Migrate to null-safety

lib/account.dart

@@ -18,11 +18,11 @@ class Account with EquatableMixin {
   }
 
   Account copyWith({
-    String scheme,
+    String? scheme,
-    String address,
+    String? address,
-    String username,
+    String? username,
-    String password,
+    String? password,
-    List<String> roots,
+    List<String>? roots,
   }) {
     return Account(
       scheme ?? this.scheme,
@@ -39,7 +39,7 @@ class Account with EquatableMixin {
         "scheme: '$scheme', "
         "address: '$address', "
         "username: '$username', "
-        "password: '${password?.isNotEmpty == true ? (kDebugMode ? password : '***') : null}', "
+        "password: '${password.isNotEmpty == true ? (kDebugMode ? password : '***') : null}', "
         "roots: List {'${roots.join('\', \'')}'}, "
         "}";
   }

lib/api/api.dart

@@ -1,7 +1,6 @@
 import 'dart:convert';
 import 'dart:typed_data';
 
-import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
@@ -43,9 +42,9 @@ class Api {
   Future<Response> request(
     String method,
     String endpoint, {
-    Map<String, String> header,
+    Map<String, String>? header,
-    String body,
+    String? body,
-    Uint8List bodyBytes,
+    Uint8List? bodyBytes,
     bool isResponseString = true,
   }) async {
     final url = _makeUri(endpoint);
@@ -114,7 +113,7 @@ class _Files {
   Api _api;
 
   Future<Response> delete({
-    @required String path,
+    required String path,
   }) async {
     try {
       return await _api.request("DELETE", path);
@@ -125,7 +124,7 @@ class _Files {
   }
 
   Future<Response> get({
-    @required String path,
+    required String path,
   }) async {
     try {
       return await _api.request("GET", path, isResponseString: false);
@@ -136,9 +135,9 @@ class _Files {
   }
 
   Future<Response> put({
-    @required String path,
+    required String path,
     String mime = "application/octet-stream",
-    Uint8List content,
+    required Uint8List content,
   }) async {
     try {
       return await _api.request(
@@ -156,8 +155,8 @@ class _Files {
   }
 
   Future<Response> propfind({
-    @required String path,
+    required String path,
-    int depth,
+    int? depth,
     getlastmodified,
     getetag,
     getcontenttype,
@@ -176,8 +175,8 @@ class _Files {
     hasPreview,
     size,
     richWorkspace,
-    Map<String, String> customNamespaces,
+    Map<String, String>? customNamespaces,
-    List<String> customProperties,
+    List<String>? customProperties,
   }) async {
     try {
       final bool hasDavNs = (getlastmodified != null ||
@@ -287,10 +286,10 @@ class _Files {
   /// [namespaces] should be specified in the format {"URI": "prefix"}, eg,
   /// {"DAV:": "d"}
   Future<Response> proppatch({
-    @required String path,
+    required String path,
-    Map<String, String> namespaces,
+    Map<String, String>? namespaces,
-    Map<String, dynamic> set,
+    Map<String, dynamic>? set,
-    List<String> remove,
+    List<String>? remove,
   }) async {
     try {
       final ns = <String, String>{
@@ -300,7 +299,7 @@ class _Files {
       builder
         ..processing("xml", "version=\"1.0\"")
         ..element("d:propertyupdate", namespaces: ns, nest: () {
-          if (set?.isNotEmpty == true) {
+          if (set != null && set.isNotEmpty) {
             builder.element("d:set", nest: () {
               builder.element("d:prop", nest: () {
                 for (final e in set.entries) {
@@ -311,7 +310,7 @@ class _Files {
               });
             });
           }
-          if (remove?.isNotEmpty == true) {
+          if (remove != null && remove.isNotEmpty) {
             builder.element("d:remove", nest: () {
               builder.element("d:prop", nest: () {
                 for (final e in remove) {
@@ -331,7 +330,7 @@ class _Files {
 
   /// A folder can be created by sending a MKCOL request to the folder
   Future<Response> mkcol({
-    @required String path,
+    required String path,
   }) async {
     try {
       return await _api.request("MKCOL", path);
@@ -344,9 +343,9 @@ class _Files {
   /// A file or folder can be copied by sending a COPY request to the file or
   /// folder and specifying the [destinationUrl] as full url
   Future<Response> copy({
-    @required String path,
+    required String path,
-    @required String destinationUrl,
+    required String destinationUrl,
-    bool overwrite,
+    bool? overwrite,
   }) async {
     try {
       return await _api.request("COPY", path, header: {
@@ -362,9 +361,9 @@ class _Files {
   /// A file or folder can be moved by sending a MOVE request to the file or
   /// folder and specifying the [destinationUrl] as full url
   Future<Response> move({
-    @required String path,
+    required String path,
-    @required String destinationUrl,
+    required String destinationUrl,
-    bool overwrite,
+    bool? overwrite,
   }) async {
     try {
       return await _api.request("MOVE", path, header: {

lib/api/api_util.dart

@@ -1,5 +1,4 @@
 /// Helper functions working with remote Nextcloud server
-import 'package:flutter/foundation.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
 import 'package:nc_photos/api/api.dart';
@@ -10,10 +9,10 @@ import 'package:nc_photos/exception.dart';
 String getFilePreviewUrl(
   Account account,
   File file, {
-  @required int width,
+  required int width,
-  @required int height,
+  required int height,
-  String mode,
+  String? mode,
-  bool a,
+  bool? a,
 }) {
   return "${account.url}/"
       "${getFilePreviewUrlRelative(file, width: width, height: height, mode: mode, a: a)}";
@@ -24,10 +23,10 @@ String getFilePreviewUrl(
 /// cropped
 String getFilePreviewUrlRelative(
   File file, {
-  @required int width,
+  required int width,
-  @required int height,
+  required int height,
-  String mode,
+  String? mode,
-  bool a,
+  bool? a,
 }) {
   String url;
   if (file.fileId != null) {
@@ -70,7 +69,7 @@ Future<String> exchangePassword(Account account) async {
     try {
       final appPwdRegex = RegExp(r"<apppassword>(.*)</apppassword>");
       final appPwdMatch = appPwdRegex.firstMatch(response.body);
-      return appPwdMatch.group(1);
+      return appPwdMatch!.group(1)!;
     } catch (_) {
       // this happens when the address is not the base URL and so Nextcloud
       // returned the login page

lib/app_db.dart

@@ -8,7 +8,6 @@ import 'package:nc_photos/entity/album/upgrader.dart';
 import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/mobile/platform.dart'
     if (dart.library.html) 'package:nc_photos/web/platform.dart' as platform;
-import 'package:nc_photos/remote_storage_util.dart' as remote_storage_util;
 import 'package:synchronized/synchronized.dart';
 
 class AppDb {
@@ -140,7 +139,7 @@ class AppDbAlbumEntry {
         upgraderV1: AlbumUpgraderV1(),
         upgraderV2: AlbumUpgraderV2(),
         upgraderV3: AlbumUpgraderV3(),
-      ),
+      )!,
     );
   }
 

lib/bloc/album_search.dart

@@ -91,12 +91,12 @@ class AlbumSearchBloc extends Bloc<AlbumSearchBlocEvent, AlbumSearchBlocState> {
     _albums = ev.albums;
     if (_lastSearch != null) {
       // search again
-      yield* _onEventSearch(_lastSearch);
+      yield* _onEventSearch(_lastSearch!);
     }
   }
 
   var _albums = <Album>[];
-  AlbumSearchBlocSearchEvent _lastSearch;
+  AlbumSearchBlocSearchEvent? _lastSearch;
 
   static final _log = Logger("bloc.album_search.AlbumSearchBloc");
 }

lib/bloc/album_search_suggestion.dart

@@ -112,12 +112,12 @@ class AlbumSearchSuggestionBloc extends Bloc<AlbumSearchSuggestionBlocEvent,
     }
     if (_lastSearch != null) {
       // search again
-      yield* _onEventSearch(_lastSearch);
+      yield* _onEventSearch(_lastSearch!);
     }
   }
 
   final _search = Woozy(limit: 5);
-  AlbumSearchSuggestionBlocSearchEvent _lastSearch;
+  AlbumSearchSuggestionBlocSearchEvent? _lastSearch;
 
   static final _log =
       Logger("bloc.album_search_suggestion.AlbumSearchSuggestionBloc");

lib/bloc/list_album.dart

@@ -47,7 +47,7 @@ abstract class ListAlbumBlocState {
         "}";
   }
 
-  final Account account;
+  final Account? account;
   final List<Album> albums;
 }
 
@@ -56,18 +56,18 @@ class ListAlbumBlocInit extends ListAlbumBlocState {
 }
 
 class ListAlbumBlocLoading extends ListAlbumBlocState {
-  const ListAlbumBlocLoading(Account account, List<Album> albums)
+  const ListAlbumBlocLoading(Account? account, List<Album> albums)
       : super(account, albums);
 }
 
 class ListAlbumBlocSuccess extends ListAlbumBlocState {
-  const ListAlbumBlocSuccess(Account account, List<Album> albums)
+  const ListAlbumBlocSuccess(Account? account, List<Album> albums)
       : super(account, albums);
 }
 
 class ListAlbumBlocFailure extends ListAlbumBlocState {
   const ListAlbumBlocFailure(
-      Account account, List<Album> albums, this.exception)
+      Account? account, List<Album> albums, this.exception)
       : super(account, albums);
 
   @override
@@ -84,7 +84,7 @@ class ListAlbumBlocFailure extends ListAlbumBlocState {
 /// The state of this bloc is inconsistent. This typically means that the data
 /// may have been changed externally
 class ListAlbumBlocInconsistent extends ListAlbumBlocState {
-  const ListAlbumBlocInconsistent(Account account, List<Album> albums)
+  const ListAlbumBlocInconsistent(Account? account, List<Album> albums)
       : super(account, albums);
 }
 
@@ -134,7 +134,7 @@ class ListAlbumBloc extends Bloc<ListAlbumBlocEvent, ListAlbumBlocState> {
     if (newState is ListAlbumBlocFailure) {
       yield ListAlbumBlocFailure(
           ev.account,
-          newState.albums?.isNotEmpty == true ? newState.albums : state.albums,
+          newState.albums.isNotEmpty ? newState.albums : state.albums,
           newState.exception);
     } else {
       yield newState;
@@ -206,9 +206,9 @@ class ListAlbumBloc extends Bloc<ListAlbumBlocEvent, ListAlbumBlocState> {
     }
   }
 
-  AppEventListener<AlbumUpdatedEvent> _albumUpdatedListener;
+  late AppEventListener<AlbumUpdatedEvent> _albumUpdatedListener;
-  AppEventListener<FileRemovedEvent> _fileRemovedListener;
+  late AppEventListener<FileRemovedEvent> _fileRemovedListener;
-  AppEventListener<AlbumCreatedEvent> _albumCreatedListener;
+  late AppEventListener<AlbumCreatedEvent> _albumCreatedListener;
 
   static final _log = Logger("bloc.list_album.ListAlbumBloc");
 }

lib/bloc/ls_dir.dart

@@ -13,9 +13,11 @@ class LsDirBlocItem {
     if (isDeep) {
       return "$runtimeType:${_toDeepString(0)}";
     } else {
+      final childrenStr =
+          children == null ? "null" : "List {length: ${children!.length}}";
       return "$runtimeType {"
           "file: '${file.path}', "
-          "children: List {length: ${children.length}}, "
+          "children: $childrenStr, "
           "}";
     }
   }
@@ -23,19 +25,19 @@ class LsDirBlocItem {
   String _toDeepString(int level) {
     String product = "\n" + " " * (level * 2) + "-${file.path}";
     if (children != null) {
-      for (final c in children) {
+      for (final c in children!) {
         product += c._toDeepString(level + 1);
       }
     }
     return product;
   }
 
-  File file;
+  final File file;
 
   /// Child directories under this directory
   ///
   /// Null if this dir is not listed, due to things like depth limitation
-  List<LsDirBlocItem> children;
+  List<LsDirBlocItem>? children;
 }
 
 abstract class LsDirBlocEvent {
@@ -59,9 +61,9 @@ class LsDirBlocQuery extends LsDirBlocEvent {
   }
 
   LsDirBlocQuery copyWith({
-    Account account,
+    Account? account,
-    File root,
+    File? root,
-    int depth,
+    int? depth,
   }) {
     return LsDirBlocQuery(
       account ?? this.account,
@@ -76,11 +78,7 @@ class LsDirBlocQuery extends LsDirBlocEvent {
 }
 
 abstract class LsDirBlocState {
-  const LsDirBlocState(this._account, this._root, this._items);
+  const LsDirBlocState(this.account, this.root, this.items);
-
-  Account get account => _account;
-  File get root => _root;
-  List<LsDirBlocItem> get items => _items;
 
   @override
   toString() {
@@ -91,9 +89,9 @@ abstract class LsDirBlocState {
         "}";
   }
 
-  final Account _account;
+  final Account? account;
-  final File _root;
+  final File root;
-  final List<LsDirBlocItem> _items;
+  final List<LsDirBlocItem> items;
 }
 
 class LsDirBlocInit extends LsDirBlocState {
@@ -101,18 +99,18 @@ class LsDirBlocInit extends LsDirBlocState {
 }
 
 class LsDirBlocLoading extends LsDirBlocState {
-  const LsDirBlocLoading(Account account, File root, List<LsDirBlocItem> items)
+  const LsDirBlocLoading(Account? account, File root, List<LsDirBlocItem> items)
       : super(account, root, items);
 }
 
 class LsDirBlocSuccess extends LsDirBlocState {
-  const LsDirBlocSuccess(Account account, File root, List<LsDirBlocItem> items)
+  const LsDirBlocSuccess(Account? account, File root, List<LsDirBlocItem> items)
       : super(account, root, items);
 }
 
 class LsDirBlocFailure extends LsDirBlocState {
   const LsDirBlocFailure(
-      Account account, File root, List<LsDirBlocItem> items, this.exception)
+      Account? account, File root, List<LsDirBlocItem> items, this.exception)
       : super(account, root, items);
 
   @override
@@ -153,12 +151,12 @@ class LsDirBloc extends Bloc<LsDirBlocEvent, LsDirBlocState> {
     var files = _cache[ev.root.path];
     if (files == null) {
       files = (await Ls(FileRepo(FileWebdavDataSource()))(ev.account, ev.root))
-          .where((f) => f.isCollection)
+          .where((f) => f.isCollection ?? false)
           .toList();
       _cache[ev.root.path] = files;
     }
     for (final f in files) {
-      List<LsDirBlocItem> children;
+      List<LsDirBlocItem>? children;
       if (ev.depth > 1) {
         children = await _query(ev.copyWith(root: f, depth: ev.depth - 1));
       }

lib/bloc/scan_dir.dart

@@ -58,10 +58,7 @@ class _ScanDirBlocExternalEvent extends ScanDirBlocEvent {
 }
 
 abstract class ScanDirBlocState {
-  const ScanDirBlocState(this._account, this._files);
+  const ScanDirBlocState(this.account, this.files);
-
-  Account get account => _account;
-  List<File> get files => _files;
 
   @override
   toString() {
@@ -71,8 +68,8 @@ abstract class ScanDirBlocState {
         "}";
   }
 
-  final Account _account;
+  final Account? account;
-  final List<File> _files;
+  final List<File> files;
 }
 
 class ScanDirBlocInit extends ScanDirBlocState {
@@ -80,17 +77,17 @@ class ScanDirBlocInit extends ScanDirBlocState {
 }
 
 class ScanDirBlocLoading extends ScanDirBlocState {
-  const ScanDirBlocLoading(Account account, List<File> files)
+  const ScanDirBlocLoading(Account? account, List<File> files)
       : super(account, files);
 }
 
 class ScanDirBlocSuccess extends ScanDirBlocState {
-  const ScanDirBlocSuccess(Account account, List<File> files)
+  const ScanDirBlocSuccess(Account? account, List<File> files)
       : super(account, files);
 }
 
 class ScanDirBlocFailure extends ScanDirBlocState {
-  const ScanDirBlocFailure(Account account, List<File> files, this.exception)
+  const ScanDirBlocFailure(Account? account, List<File> files, this.exception)
       : super(account, files);
 
   @override
@@ -107,7 +104,7 @@ class ScanDirBlocFailure extends ScanDirBlocState {
 /// The state of this bloc is inconsistent. This typically means that the data
 /// may have been changed externally
 class ScanDirBlocInconsistent extends ScanDirBlocState {
-  const ScanDirBlocInconsistent(Account account, List<File> files)
+  const ScanDirBlocInconsistent(Account? account, List<File> files)
       : super(account, files);
 }
 
@@ -285,11 +282,12 @@ class ScanDirBloc extends Bloc<ScanDirBlocEvent, ScanDirBlocState> {
     }
   }
 
-  AppEventListener<FileRemovedEvent> _fileRemovedEventListener;
+  late AppEventListener<FileRemovedEvent> _fileRemovedEventListener;
-  AppEventListener<FilePropertyUpdatedEvent> _filePropertyUpdatedEventListener;
+  late AppEventListener<FilePropertyUpdatedEvent>
+      _filePropertyUpdatedEventListener;
 
   int _successivePropertyUpdatedCount = 0;
-  StreamSubscription<void> _propertyUpdatedSubscription;
+  StreamSubscription<void>? _propertyUpdatedSubscription;
 
   bool _shouldCheckCache = true;
 

lib/cache_manager_util.dart

@@ -7,12 +7,16 @@ class CancelableGetFile {
 
   Future<FileInfo> getFileUntil(String key,
       {bool ignoreMemCache = false}) async {
-    FileInfo product;
+    FileInfo? product;
     while (product == null && _shouldRun) {
       product = await store.getFile(key, ignoreMemCache: ignoreMemCache);
       await Future.delayed(Duration(milliseconds: 500));
     }
-    return product ?? Future.error("Interrupted");
+    if (product == null) {
+      return Future.error("Interrupted");
+    } else {
+      return product;
+    }
   }
 
   void cancel() {

lib/entity/album.dart

@@ -2,7 +2,6 @@ import 'dart:convert';
 import 'dart:math';
 
 import 'package:equatable/equatable.dart';
-import 'package:flutter/foundation.dart';
 import 'package:idb_sqflite/idb_sqflite.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
@@ -31,57 +30,57 @@ bool isAlbumFile(Account account, File file) =>
 /// Immutable object that represents an album
 class Album with EquatableMixin {
   Album({
-    DateTime lastUpdated,
+    DateTime? lastUpdated,
-    @required String name,
+    required this.name,
-    @required this.provider,
+    required this.provider,
-    @required this.coverProvider,
+    required this.coverProvider,
-    @required this.sortProvider,
+    required this.sortProvider,
     this.albumFile,
-  })  : this.lastUpdated = (lastUpdated ?? DateTime.now()).toUtc(),
+  }) : this.lastUpdated = (lastUpdated ?? DateTime.now()).toUtc();
-        this.name = name ?? "";
 
-  factory Album.fromJson(
+  static Album? fromJson(
     Map<String, dynamic> json, {
-    AlbumUpgraderV1 upgraderV1,
+    required AlbumUpgraderV1? upgraderV1,
-    AlbumUpgraderV2 upgraderV2,
+    required AlbumUpgraderV2? upgraderV2,
-    AlbumUpgraderV3 upgraderV3,
+    required AlbumUpgraderV3? upgraderV3,
   }) {
     final jsonVersion = json["version"];
+    Map<String, dynamic>? result = json;
     if (jsonVersion < 2) {
-      json = upgraderV1?.call(json);
+      result = upgraderV1?.call(result);
-      if (json == null) {
+      if (result == null) {
         _log.info("[fromJson] Version $jsonVersion not compatible");
         return null;
       }
     }
     if (jsonVersion < 3) {
-      json = upgraderV2?.call(json);
+      result = upgraderV2?.call(result);
-      if (json == null) {
+      if (result == null) {
         _log.info("[fromJson] Version $jsonVersion not compatible");
         return null;
       }
     }
     if (jsonVersion < 4) {
-      json = upgraderV3?.call(json);
+      result = upgraderV3?.call(result);
-      if (json == null) {
+      if (result == null) {
         _log.info("[fromJson] Version $jsonVersion not compatible");
         return null;
       }
     }
     return Album(
-      lastUpdated: json["lastUpdated"] == null
+      lastUpdated: result["lastUpdated"] == null
           ? null
-          : DateTime.parse(json["lastUpdated"]),
+          : DateTime.parse(result["lastUpdated"]),
-      name: json["name"],
+      name: result["name"],
       provider:
-          AlbumProvider.fromJson(json["provider"].cast<String, dynamic>()),
+          AlbumProvider.fromJson(result["provider"].cast<String, dynamic>()),
       coverProvider: AlbumCoverProvider.fromJson(
-          json["coverProvider"].cast<String, dynamic>()),
+          result["coverProvider"].cast<String, dynamic>()),
       sortProvider: AlbumSortProvider.fromJson(
-          json["sortProvider"].cast<String, dynamic>()),
+          result["sortProvider"].cast<String, dynamic>()),
-      albumFile: json["albumFile"] == null
+      albumFile: result["albumFile"] == null
           ? null
-          : File.fromJson(json["albumFile"].cast<String, dynamic>()),
+          : File.fromJson(result["albumFile"].cast<String, dynamic>()),
     );
   }
 
@@ -103,12 +102,12 @@ class Album with EquatableMixin {
   /// will be used. In order to keep [lastUpdated], you must explicitly assign
   /// it with value from this or a null value
   Album copyWith({
-    OrNull<DateTime> lastUpdated,
+    OrNull<DateTime>? lastUpdated,
-    String name,
+    String? name,
-    AlbumProvider provider,
+    AlbumProvider? provider,
-    AlbumCoverProvider coverProvider,
+    AlbumCoverProvider? coverProvider,
-    AlbumSortProvider sortProvider,
+    AlbumSortProvider? sortProvider,
-    File albumFile,
+    File? albumFile,
   }) {
     return Album(
       lastUpdated:
@@ -141,7 +140,7 @@ class Album with EquatableMixin {
       "provider": provider.toJson(),
       "coverProvider": coverProvider.toJson(),
       "sortProvider": sortProvider.toJson(),
-      if (albumFile != null) "albumFile": albumFile.toJson(),
+      if (albumFile != null) "albumFile": albumFile!.toJson(),
     };
   }
 
@@ -165,7 +164,7 @@ class Album with EquatableMixin {
   /// How is this album stored on server
   ///
   /// This field is typically only meaningful when returned by [AlbumRepo.get]
-  final File albumFile;
+  final File? albumFile;
 
   /// versioning of this class, use to upgrade old persisted album
   static const version = 4;
@@ -224,7 +223,8 @@ class AlbumRemoteDataSource implements AlbumDataSource {
         upgraderV1: AlbumUpgraderV1(),
         upgraderV2: AlbumUpgraderV2(),
         upgraderV3: AlbumUpgraderV3(),
-      ).copyWith(
+      )!
+          .copyWith(
         lastUpdated: OrNull(null),
         albumFile: albumFile,
       );
@@ -245,8 +245,8 @@ class AlbumRemoteDataSource implements AlbumDataSource {
     final filePath =
         "${remote_storage_util.getRemoteAlbumsDir(account)}/$fileName";
     final fileRepo = FileRepo(FileWebdavDataSource());
-    await PutFileBinary(fileRepo)(
+    await PutFileBinary(fileRepo)(account, filePath,
-        account, filePath, utf8.encode(jsonEncode(album.toRemoteJson())),
+        Utf8Encoder().convert(jsonEncode(album.toRemoteJson())),
         shouldCreateMissingDir: true);
     // query album file
     final list = await Ls(fileRepo)(account, File(path: filePath),
@@ -256,10 +256,10 @@ class AlbumRemoteDataSource implements AlbumDataSource {
 
   @override
   update(Account account, Album album) async {
-    _log.info("[update] ${album.albumFile.path}");
+    _log.info("[update] ${album.albumFile!.path}");
     final fileRepo = FileRepo(FileWebdavDataSource());
-    await PutFileBinary(fileRepo)(account, album.albumFile.path,
+    await PutFileBinary(fileRepo)(account, album.albumFile!.path,
-        utf8.encode(jsonEncode(album.toRemoteJson())));
+        Utf8Encoder().convert(jsonEncode(album.toRemoteJson())));
   }
 
   @override
@@ -286,7 +286,7 @@ class AlbumAppDbDataSource implements AlbumDataSource {
       final path = AppDbAlbumEntry.toPathFromFile(account, albumFile);
       final range = KeyRange.bound([path, 0], [path, int_util.int32Max]);
       final List results = await index.getAll(range);
-      if (results?.isNotEmpty == true) {
+      if (results.isNotEmpty == true) {
         final entries = results
             .map((e) => AppDbAlbumEntry.fromJson(e.cast<String, dynamic>()));
         if (entries.length > 1) {
@@ -317,7 +317,7 @@ class AlbumAppDbDataSource implements AlbumDataSource {
 
   @override
   update(Account account, Album album) {
-    _log.info("[update] ${album.albumFile.path}");
+    _log.info("[update] ${album.albumFile!.path}");
     return AppDb.use((db) async {
       final transaction =
           db.transaction(AppDb.albumStoreName, idbModeReadWrite);
@@ -337,8 +337,8 @@ class AlbumCachedDataSource implements AlbumDataSource {
   get(Account account, File albumFile) async {
     try {
       final cache = await _appDbSrc.get(account, albumFile);
-      if (cache.albumFile.etag?.isNotEmpty == true &&
+      if (cache.albumFile!.etag?.isNotEmpty == true &&
-          cache.albumFile.etag == albumFile.etag) {
+          cache.albumFile!.etag == albumFile.etag) {
         // cache is good
         _log.fine(
             "[get] etag matched for ${AppDbAlbumEntry.toPathFromFile(account, albumFile)}");
@@ -412,7 +412,7 @@ class AlbumCachedDataSource implements AlbumDataSource {
 Future<void> _cacheAlbum(
     ObjectStore store, Account account, Album album) async {
   final index = store.index(AppDbAlbumEntry.indexName);
-  final path = AppDbAlbumEntry.toPathFromFile(account, album.albumFile);
+  final path = AppDbAlbumEntry.toPathFromFile(account, album.albumFile!);
   final range = KeyRange.bound([path, 0], [path, int_util.int32Max]);
   // count number of entries for this album
   final count = await index.count(range);
@@ -441,7 +441,7 @@ Future<void> _cacheAlbum(
   for (final e in entries) {
     _log.info("[_cacheAlbum] Caching ${e.path}[${e.index}]");
     await store.put(e.toJson(),
-        AppDbAlbumEntry.toPrimaryKey(account, e.album.albumFile, e.index));
+        AppDbAlbumEntry.toPrimaryKey(account, e.album.albumFile!, e.index));
   }
 
   if (count > entries.length) {

lib/entity/album/cover_provider.dart

@@ -40,7 +40,7 @@ abstract class AlbumCoverProvider with EquatableMixin {
   @override
   toString();
 
-  File getCover(Album album);
+  File? getCover(Album album);
 
   Map<String, dynamic> _toContentJson();
 
@@ -68,7 +68,8 @@ class AlbumAutoCoverProvider extends AlbumCoverProvider {
         "}";
   }
 
-  File getCover(Album album) {
+  @override
+  getCover(Album album) {
     if (coverFile == null) {
       try {
         // use the latest file as cover
@@ -77,7 +78,8 @@ class AlbumAutoCoverProvider extends AlbumCoverProvider {
             .whereType<AlbumFileItem>()
             .map((e) => e.file)
             .where((element) =>
-                file_util.isSupportedFormat(element) && element.hasPreview)
+                file_util.isSupportedFormat(element) &&
+                (element.hasPreview ?? false))
             .sorted(compareFileDateTimeDescending)
             .first;
       } catch (_) {
@@ -96,11 +98,11 @@ class AlbumAutoCoverProvider extends AlbumCoverProvider {
   @override
   _toContentJson() {
     return {
-      if (coverFile != null) "coverFile": coverFile.toJson(),
+      if (coverFile != null) "coverFile": coverFile!.toJson(),
     };
   }
 
-  final File coverFile;
+  final File? coverFile;
 
   static const _type = "auto";
 }

lib/entity/album/item.dart

@@ -1,7 +1,6 @@
 import 'dart:math';
 
 import 'package:equatable/equatable.dart';
-import 'package:flutter/foundation.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/list_extension.dart';
@@ -60,18 +59,16 @@ abstract class AlbumItem {
 
 class AlbumFileItem extends AlbumItem with EquatableMixin {
   AlbumFileItem({
-    @required this.file,
+    required this.file,
   });
 
   @override
   // ignore: hash_and_equals
-  bool operator ==(Object other) => equals(other, isDeep: true);
+  bool operator ==(Object? other) => equals(other, isDeep: true);
 
-  bool equals(Object other, {bool isDeep = false}) {
+  bool equals(Object? other, {bool isDeep = false}) {
     if (other is AlbumFileItem) {
-      return super == other &&
+      return super == other && (file.equals(other.file, isDeep: isDeep));
-          (file == null) == (other.file == null) &&
-          (file?.equals(other.file, isDeep: isDeep) ?? true);
     } else {
       return false;
     }
@@ -109,7 +106,7 @@ class AlbumFileItem extends AlbumItem with EquatableMixin {
 
 class AlbumLabelItem extends AlbumItem with EquatableMixin {
   AlbumLabelItem({
-    @required this.text,
+    required this.text,
   });
 
   factory AlbumLabelItem.fromJson(Map<String, dynamic> json) {

lib/entity/album/provider.dart

@@ -50,7 +50,7 @@ abstract class AlbumProvider with EquatableMixin {
   toString({bool isDeep = false});
 
   /// Return the date time associated with the latest item, or null
-  DateTime get latestItemTime;
+  DateTime? get latestItemTime;
 
   AlbumProvider copyWith();
 
@@ -59,7 +59,7 @@ abstract class AlbumProvider with EquatableMixin {
 
 class AlbumStaticProvider extends AlbumProvider {
   AlbumStaticProvider({
-    @required List<AlbumItem> items,
+    required List<AlbumItem> items,
   }) : this.items = UnmodifiableListView(items);
 
   factory AlbumStaticProvider.fromJson(Map<String, dynamic> json) {
@@ -90,7 +90,9 @@ class AlbumStaticProvider extends AlbumProvider {
   }
 
   @override
-  AlbumStaticProvider copyWith({List<AlbumItem> items}) {
+  AlbumStaticProvider copyWith({
+    List<AlbumItem>? items,
+  }) {
     return AlbumStaticProvider(
       items: items ?? this.items,
     );
@@ -124,7 +126,7 @@ class AlbumStaticProvider extends AlbumProvider {
 
 abstract class AlbumDynamicProvider extends AlbumProvider {
   AlbumDynamicProvider({
-    DateTime latestItemTime,
+    DateTime? latestItemTime,
   }) : _latestItemTime = latestItemTime;
 
   @override
@@ -137,13 +139,13 @@ abstract class AlbumDynamicProvider extends AlbumProvider {
   @override
   toContentJson() {
     return {
-      "latestItemTime": _latestItemTime?.toUtc()?.toIso8601String(),
+      "latestItemTime": _latestItemTime?.toUtc().toIso8601String(),
     };
   }
 
   @override
   AlbumDynamicProvider copyWith({
-    DateTime latestItemTime,
+    DateTime? latestItemTime,
   });
 
   @override
@@ -154,13 +156,13 @@ abstract class AlbumDynamicProvider extends AlbumProvider {
         _latestItemTime,
       ];
 
-  final DateTime _latestItemTime;
+  final DateTime? _latestItemTime;
 }
 
 class AlbumDirProvider extends AlbumDynamicProvider {
   AlbumDirProvider({
-    @required this.dirs,
+    required this.dirs,
-    DateTime latestItemTime,
+    DateTime? latestItemTime,
   }) : super(latestItemTime: latestItemTime);
 
   factory AlbumDirProvider.fromJson(Map<String, dynamic> json) {
@@ -192,8 +194,8 @@ class AlbumDirProvider extends AlbumDynamicProvider {
 
   @override
   AlbumDirProvider copyWith({
-    List<File> dirs,
+    List<File>? dirs,
-    DateTime latestItemTime,
+    DateTime? latestItemTime,
   }) {
     return AlbumDirProvider(
       dirs: dirs ?? this.dirs,

lib/entity/album/sort_provider.dart

@@ -1,5 +1,4 @@
 import 'package:equatable/equatable.dart';
-import 'package:flutter/foundation.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/entity/album/item.dart';
 import 'package:nc_photos/entity/file.dart';
@@ -80,7 +79,7 @@ class AlbumNullSortProvider extends AlbumSortProvider {
 
 abstract class AlbumReversibleSortProvider extends AlbumSortProvider {
   const AlbumReversibleSortProvider({
-    @required this.isAscending,
+    required this.isAscending,
   });
 
   @override
@@ -108,7 +107,7 @@ abstract class AlbumReversibleSortProvider extends AlbumSortProvider {
 /// Sort based on the time of the files
 class AlbumTimeSortProvider extends AlbumReversibleSortProvider {
   const AlbumTimeSortProvider({
-    bool isAscending,
+    required bool isAscending,
   }) : super(isAscending: isAscending);
 
   factory AlbumTimeSortProvider.fromJson(Map<String, dynamic> json) {
@@ -126,7 +125,7 @@ class AlbumTimeSortProvider extends AlbumReversibleSortProvider {
 
   @override
   sort(List<AlbumItem> items) {
-    DateTime prevFileTime;
+    DateTime? prevFileTime;
     return items
         .map((e) {
           if (e is AlbumFileItem) {
@@ -139,16 +138,16 @@ class AlbumTimeSortProvider extends AlbumReversibleSortProvider {
         .stableSorted((x, y) {
           if (x.item1 == null && y.item1 == null) {
             return 0;
-          }
+          } else if (x.item1 == null) {
-          else if (x.item1 == null) {
             return -1;
           } else if (y.item1 == null) {
             return 1;
-          }
-          if (isAscending) {
-            return x.item1.compareTo(y.item1);
           } else {
-            return y.item1.compareTo(x.item1);
+            if (isAscending) {
+              return x.item1!.compareTo(y.item1!);
+            } else {
+              return y.item1!.compareTo(x.item1!);
+            }
           }
         })
         .map((e) => e.item2)

lib/entity/album/upgrader.dart

@@ -1,7 +1,7 @@
 import 'package:logging/logging.dart';
 
 abstract class AlbumUpgrader {
-  Map<String, dynamic> call(Map<String, dynamic> json);
+  Map<String, dynamic>? call(Map<String, dynamic> json);
 }
 
 /// Upgrade v1 Album to v2
@@ -10,7 +10,8 @@ class AlbumUpgraderV1 implements AlbumUpgrader {
     this.logFilePath,
   });
 
-  Map<String, dynamic> call(Map<String, dynamic> json) {
+  @override
+  call(Map<String, dynamic> json) {
     // v1 album items are corrupted in one of the updates, drop it
     _log.fine("[call] Upgrade v1 Album for file: $logFilePath");
     final result = Map<String, dynamic>.from(json);
@@ -19,7 +20,7 @@ class AlbumUpgraderV1 implements AlbumUpgrader {
   }
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
   static final _log = Logger("entity.album.upgrader.AlbumUpgraderV1");
 }
@@ -30,7 +31,8 @@ class AlbumUpgraderV2 implements AlbumUpgrader {
     this.logFilePath,
   });
 
-  Map<String, dynamic> call(Map<String, dynamic> json) {
+  @override
+  call(Map<String, dynamic> json) {
     // move v2 items to v3 provider
     _log.fine("[call] Upgrade v2 Album for file: $logFilePath");
     final result = Map<String, dynamic>.from(json);
@@ -51,7 +53,7 @@ class AlbumUpgraderV2 implements AlbumUpgrader {
   }
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
   static final _log = Logger("entity.album.upgrader.AlbumUpgraderV2");
 }
@@ -62,7 +64,8 @@ class AlbumUpgraderV3 implements AlbumUpgrader {
     this.logFilePath,
   });
 
-  Map<String, dynamic> call(Map<String, dynamic> json) {
+  @override
+  call(Map<String, dynamic> json) {
     // move v3 items to v4 provider
     _log.fine("[call] Upgrade v3 Album for file: $logFilePath");
     final result = Map<String, dynamic>.from(json);
@@ -77,7 +80,7 @@ class AlbumUpgraderV3 implements AlbumUpgrader {
   }
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
   static final _log = Logger("entity.album.upgrader.AlbumUpgraderV3");
 }

lib/entity/exif.dart

@@ -9,14 +9,14 @@ class Exif with EquatableMixin {
 
   @override
   // ignore: hash_and_equals
-  bool operator ==(Object other) => equals(other, isDeep: true);
+  bool operator ==(Object? other) => equals(other, isDeep: true);
 
   /// Compare two Exif objects
   ///
   /// If [isDeep] is false, two Exif objects are considered identical if they
   /// contain the same number of fields. This hack is to save time comparing a
   /// large amount of data that are mostly immutable
-  bool equals(Object other, {bool isDeep = false}) {
+  bool equals(Object? other, {bool isDeep = false}) {
     if (isDeep) {
       return super == other;
     } else {
@@ -87,33 +87,33 @@ class Exif with EquatableMixin {
   }
 
   /// 0x010f Make
-  String get make => data["Make"];
+  String? get make => data["Make"];
 
   /// 0x0110 Model
-  String get model => data["Model"];
+  String? get model => data["Model"];
 
   /// 0x9003 DateTimeOriginal
-  DateTime get dateTimeOriginal => data.containsKey("DateTimeOriginal")
+  DateTime? get dateTimeOriginal => data.containsKey("DateTimeOriginal")
       ? dateTimeFormat.parse(data["DateTimeOriginal"]).toUtc()
       : null;
 
   /// 0x829a ExposureTime
-  Rational get exposureTime => data["ExposureTime"];
+  Rational? get exposureTime => data["ExposureTime"];
 
   /// 0x829d FNumber
-  Rational get fNumber => data["FNumber"];
+  Rational? get fNumber => data["FNumber"];
 
   /// 0x8827 ISO/ISOSpeedRatings/PhotographicSensitivity
-  int get isoSpeedRatings => data["ISOSpeedRatings"];
+  int? get isoSpeedRatings => data["ISOSpeedRatings"];
 
   /// 0x920a FocalLength
-  Rational get focalLength => data["FocalLength"];
+  Rational? get focalLength => data["FocalLength"];
 
   /// 0x8825 GPS tags
-  String get gpsLatitudeRef => data["GPSLatitudeRef"];
+  String? get gpsLatitudeRef => data["GPSLatitudeRef"];
-  List<Rational> get gpsLatitude => data["GPSLatitude"].cast<Rational>();
+  List<Rational>? get gpsLatitude => data["GPSLatitude"].cast<Rational>();
-  String get gpsLongitudeRef => data["GPSLongitudeRef"];
+  String? get gpsLongitudeRef => data["GPSLongitudeRef"];
-  List<Rational> get gpsLongitude => data["GPSLongitude"].cast<Rational>();
+  List<Rational>? get gpsLongitude => data["GPSLongitude"].cast<Rational>();
 
   @override
   get props => [

lib/entity/file.dart

@@ -1,7 +1,6 @@
 import 'dart:typed_data';
 
 import 'package:equatable/equatable.dart';
-import 'package:flutter/foundation.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
 import 'package:nc_photos/entity/exif.dart';
@@ -21,7 +20,7 @@ int compareFileDateTimeDescending(File x, File y) {
 /// Immutable object that hold metadata of a [File]
 class Metadata with EquatableMixin {
   Metadata({
-    DateTime lastUpdated,
+    DateTime? lastUpdated,
     this.fileEtag,
     this.imageWidth,
     this.imageHeight,
@@ -30,9 +29,9 @@ class Metadata with EquatableMixin {
 
   @override
   // ignore: hash_and_equals
-  bool operator ==(Object other) => equals(other, isDeep: true);
+  bool operator ==(Object? other) => equals(other, isDeep: true);
 
-  bool equals(Object other, {bool isDeep = false}) {
+  bool equals(Object? other, {bool isDeep = false}) {
     if (other is Metadata) {
       return super == other &&
           (exif == null) == (other.exif == null) &&
@@ -48,36 +47,37 @@ class Metadata with EquatableMixin {
   /// corresponding upgrader will be called one by one to upgrade the json,
   /// version by version until it reached the active version. If any upgrader
   /// in the chain is null, the upgrade process will fail
-  factory Metadata.fromJson(
+  static Metadata? fromJson(
     Map<String, dynamic> json, {
-    MetadataUpgraderV1 upgraderV1,
+    required MetadataUpgraderV1? upgraderV1,
-    MetadataUpgraderV2 upgraderV2,
+    required MetadataUpgraderV2? upgraderV2,
   }) {
     final jsonVersion = json["version"];
+    Map<String, dynamic>? result = json;
     if (jsonVersion < 2) {
-      json = upgraderV1?.call(json);
+      result = upgraderV1?.call(result);
-      if (json == null) {
+      if (result == null) {
         _log.info("[fromJson] Version $jsonVersion not compatible");
         return null;
       }
     }
     if (jsonVersion < 3) {
-      json = upgraderV2?.call(json);
+      result = upgraderV2?.call(result);
-      if (json == null) {
+      if (result == null) {
         _log.info("[fromJson] Version $jsonVersion not compatible");
         return null;
       }
     }
     return Metadata(
-      lastUpdated: json["lastUpdated"] == null
+      lastUpdated: result["lastUpdated"] == null
           ? null
-          : DateTime.parse(json["lastUpdated"]),
+          : DateTime.parse(result["lastUpdated"]),
-      fileEtag: json["fileEtag"],
+      fileEtag: result["fileEtag"],
-      imageWidth: json["imageWidth"],
+      imageWidth: result["imageWidth"],
-      imageHeight: json["imageHeight"],
+      imageHeight: result["imageHeight"],
-      exif: json["exif"] == null
+      exif: result["exif"] == null
           ? null
-          : Exif.fromJson(json["exif"].cast<String, dynamic>()),
+          : Exif.fromJson(result["exif"].cast<String, dynamic>()),
     );
   }
 
@@ -88,7 +88,7 @@ class Metadata with EquatableMixin {
       if (fileEtag != null) "fileEtag": fileEtag,
       if (imageWidth != null) "imageWidth": imageWidth,
       if (imageHeight != null) "imageHeight": imageHeight,
-      if (exif != null) "exif": exif.toJson(),
+      if (exif != null) "exif": exif!.toJson(),
     };
   }
 
@@ -123,10 +123,10 @@ class Metadata with EquatableMixin {
   final DateTime lastUpdated;
 
   /// Etag of the parent file when the metadata is saved
-  final String fileEtag;
+  final String? fileEtag;
-  final int imageWidth;
+  final int? imageWidth;
-  final int imageHeight;
+  final int? imageHeight;
-  final Exif exif;
+  final Exif? exif;
 
   /// versioning of this class, use to upgrade old persisted metadata
   static const version = 3;
@@ -135,17 +135,17 @@ class Metadata with EquatableMixin {
 }
 
 abstract class MetadataUpgrader {
-  Map<String, dynamic> call(Map<String, dynamic> json);
+  Map<String, dynamic>? call(Map<String, dynamic> json);
 }
 
 /// Upgrade v1 Metadata to v2
 class MetadataUpgraderV1 implements MetadataUpgrader {
   MetadataUpgraderV1({
-    @required this.fileContentType,
+    required this.fileContentType,
     this.logFilePath,
   });
 
-  Map<String, dynamic> call(Map<String, dynamic> json) {
+  Map<String, dynamic>? call(Map<String, dynamic> json) {
     if (fileContentType == "image/webp") {
       // Version 1 metadata for webp is bugged, drop it
       _log.fine("[call] Upgrade v1 metadata for file: $logFilePath");
@@ -155,10 +155,10 @@ class MetadataUpgraderV1 implements MetadataUpgrader {
     }
   }
 
-  final String fileContentType;
+  final String? fileContentType;
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
   static final _log = Logger("entity.file.MetadataUpgraderV1");
 }
@@ -166,11 +166,11 @@ class MetadataUpgraderV1 implements MetadataUpgrader {
 /// Upgrade v2 Metadata to v3
 class MetadataUpgraderV2 implements MetadataUpgrader {
   MetadataUpgraderV2({
-    @required this.fileContentType,
+    required this.fileContentType,
     this.logFilePath,
   });
 
-  Map<String, dynamic> call(Map<String, dynamic> json) {
+  Map<String, dynamic>? call(Map<String, dynamic> json) {
     if (fileContentType == "image/jpeg") {
       // Version 2 metadata for jpeg doesn't consider orientation
       if (json["exif"] != null && json["exif"].containsKey("Orientation")) {
@@ -187,17 +187,17 @@ class MetadataUpgraderV2 implements MetadataUpgrader {
     return json;
   }
 
-  final String fileContentType;
+  final String? fileContentType;
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
   static final _log = Logger("entity.file.MetadataUpgraderV2");
 }
 
 class File with EquatableMixin {
   File({
-    @required String path,
+    required String path,
     this.contentLength,
     this.contentType,
     this.etag,
@@ -214,9 +214,9 @@ class File with EquatableMixin {
 
   @override
   // ignore: hash_and_equals
-  bool operator ==(Object other) => equals(other, isDeep: true);
+  bool operator ==(Object? other) => equals(other, isDeep: true);
 
-  bool equals(Object other, {bool isDeep = false}) {
+  bool equals(Object? other, {bool isDeep = false}) {
     if (other is File) {
       return super == other &&
           (metadata == null) == (other.metadata == null) &&
@@ -310,33 +310,33 @@ class File with EquatableMixin {
       if (contentType != null) "contentType": contentType,
       if (etag != null) "etag": etag,
       if (lastModified != null)
-        "lastModified": lastModified.toUtc().toIso8601String(),
+        "lastModified": lastModified!.toUtc().toIso8601String(),
       if (isCollection != null) "isCollection": isCollection,
       if (usedBytes != null) "usedBytes": usedBytes,
       if (hasPreview != null) "hasPreview": hasPreview,
       if (fileId != null) "fileId": fileId,
       if (ownerId != null) "ownerId": ownerId,
-      if (metadata != null) "metadata": metadata.toJson(),
+      if (metadata != null) "metadata": metadata!.toJson(),
       if (isArchived != null) "isArchived": isArchived,
       if (overrideDateTime != null)
-        "overrideDateTime": overrideDateTime.toUtc().toIso8601String(),
+        "overrideDateTime": overrideDateTime!.toUtc().toIso8601String(),
     };
   }
 
   File copyWith({
-    String path,
+    String? path,
-    int contentLength,
+    int? contentLength,
-    String contentType,
+    String? contentType,
-    String etag,
+    String? etag,
-    DateTime lastModified,
+    DateTime? lastModified,
-    bool isCollection,
+    bool? isCollection,
-    int usedBytes,
+    int? usedBytes,
-    bool hasPreview,
+    bool? hasPreview,
-    int fileId,
+    int? fileId,
-    String ownerId,
+    String? ownerId,
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) {
     return File(
       path: path ?? this.path,
@@ -392,20 +392,20 @@ class File with EquatableMixin {
       ];
 
   final String path;
-  final int contentLength;
+  final int? contentLength;
-  final String contentType;
+  final String? contentType;
-  final String etag;
+  final String? etag;
-  final DateTime lastModified;
+  final DateTime? lastModified;
-  final bool isCollection;
+  final bool? isCollection;
-  final int usedBytes;
+  final int? usedBytes;
-  final bool hasPreview;
+  final bool? hasPreview;
   // maybe null when loaded from old cache
-  final int fileId;
+  final int? fileId;
-  final String ownerId;
+  final String? ownerId;
   // metadata
-  final Metadata metadata;
+  final Metadata? metadata;
-  final bool isArchived;
+  final bool? isArchived;
-  final DateTime overrideDateTime;
+  final DateTime? overrideDateTime;
 }
 
 extension FileExtension on File {
@@ -442,9 +442,9 @@ class FileRepo {
   Future<void> updateProperty(
     Account account,
     File file, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) =>
       this.dataSrc.updateProperty(
             account,
@@ -459,7 +459,7 @@ class FileRepo {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) =>
       this.dataSrc.copy(
             account,
@@ -473,7 +473,7 @@ class FileRepo {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) =>
       this.dataSrc.move(
             account,
@@ -506,9 +506,9 @@ abstract class FileDataSource {
   Future<void> updateProperty(
     Account account,
     File f, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   });
 
   /// Copy [f] to [destination]
@@ -519,7 +519,7 @@ abstract class FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   });
 
   /// Move [f] to [destination]
@@ -530,7 +530,7 @@ abstract class FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   });
 
   /// Create a directory at [path]

lib/entity/file/data_source.dart

@@ -1,7 +1,6 @@
 import 'dart:convert';
 import 'dart:typed_data';
 
-import 'package:flutter/foundation.dart';
 import 'package:idb_shim/idb_client.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
@@ -27,7 +26,7 @@ class FileWebdavDataSource implements FileDataSource {
   list(
     Account account,
     File f, {
-    int depth,
+    int? depth,
   }) async {
     _log.fine("[list] ${f.path}");
     final response = await Api(account).files().propfind(
@@ -61,7 +60,7 @@ class FileWebdavDataSource implements FileDataSource {
     final files = WebdavFileParser()(xml);
     // _log.fine("[list] Parsed files: [$files]");
     return files.where((element) => _validateFile(element)).map((e) {
-      if (e.metadata == null || e.metadata.fileEtag == e.etag) {
+      if (e.metadata == null || e.metadata!.fileEtag == e.etag) {
         return e;
       } else {
         _log.info("[list] Ignore outdated metadata for ${e.path}");
@@ -112,27 +111,27 @@ class FileWebdavDataSource implements FileDataSource {
   updateProperty(
     Account account,
     File f, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) async {
     _log.info("[updateProperty] ${f.path}");
-    if (metadata?.obj != null && metadata.obj.fileEtag != f.etag) {
+    if (metadata?.obj != null && metadata!.obj!.fileEtag != f.etag) {
       _log.warning(
-          "[updateProperty] Metadata etag mismatch (metadata: ${metadata.obj.fileEtag}, file: ${f.etag})");
+          "[updateProperty] Metadata etag mismatch (metadata: ${metadata.obj!.fileEtag}, file: ${f.etag})");
     }
     final setProps = {
       if (metadata?.obj != null)
-        "app:metadata": jsonEncode(metadata.obj.toJson()),
+        "app:metadata": jsonEncode(metadata!.obj!.toJson()),
-      if (isArchived?.obj != null) "app:is-archived": isArchived.obj,
+      if (isArchived?.obj != null) "app:is-archived": isArchived!.obj,
       if (overrideDateTime?.obj != null)
         "app:override-date-time":
-            overrideDateTime.obj.toUtc().toIso8601String(),
+            overrideDateTime!.obj!.toUtc().toIso8601String(),
     };
     final removeProps = [
-      if (OrNull.isNull(metadata)) "app:metadata",
+      if (OrNull.isSetNull(metadata)) "app:metadata",
-      if (OrNull.isNull(isArchived)) "app:is-archived",
+      if (OrNull.isSetNull(isArchived)) "app:is-archived",
-      if (OrNull.isNull(overrideDateTime)) "app:override-date-time",
+      if (OrNull.isSetNull(overrideDateTime)) "app:override-date-time",
     ];
     final response = await Api(account).files().proppatch(
           path: f.path,
@@ -155,7 +154,7 @@ class FileWebdavDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     _log.info("[copy] ${f.path} to $destination");
     final response = await Api(account).files().copy(
@@ -176,7 +175,7 @@ class FileWebdavDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     _log.info("[move] ${f.path} to $destination");
     final response = await Api(account).files().move(
@@ -256,9 +255,9 @@ class FileAppDbDataSource implements FileDataSource {
   updateProperty(
     Account account,
     File f, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) {
     _log.info("[updateProperty] ${f.path}");
     return AppDb.use((db) async {
@@ -300,7 +299,7 @@ class FileAppDbDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     // do nothing
   }
@@ -310,7 +309,7 @@ class FileAppDbDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     // do nothing
   }
@@ -325,7 +324,7 @@ class FileAppDbDataSource implements FileDataSource {
     final path = AppDbFileEntry.toPath(account, f);
     final range = KeyRange.bound([path, 0], [path, int_util.int32Max]);
     final List results = await index.getAll(range);
-    if (results?.isNotEmpty == true) {
+    if (results.isNotEmpty == true) {
       final entries = results
           .map((e) => AppDbFileEntry.fromJson(e.cast<String, dynamic>()));
       return entries
@@ -358,7 +357,7 @@ class FileCachedDataSource implements FileDataSource {
     );
     final cache = await cacheManager.list(account, f);
     if (cacheManager.isGood) {
-      return cache;
+      return cache!;
     }
 
     // no cache or outdated
@@ -426,9 +425,9 @@ class FileCachedDataSource implements FileDataSource {
   updateProperty(
     Account account,
     File f, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) async {
     await _remoteSrc
         .updateProperty(
@@ -462,7 +461,7 @@ class FileCachedDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     await _remoteSrc.copy(account, f, destination,
         shouldOverwrite: shouldOverwrite);
@@ -473,7 +472,7 @@ class FileCachedDataSource implements FileDataSource {
     Account account,
     File f,
     String destination, {
-    bool shouldOverwrite,
+    bool? shouldOverwrite,
   }) async {
     await _remoteSrc.move(account, f, destination,
         shouldOverwrite: shouldOverwrite);
@@ -599,17 +598,17 @@ class FileCachedDataSource implements FileDataSource {
 
 class _CacheManager {
   _CacheManager({
-    @required this.appDbSrc,
+    required this.appDbSrc,
-    @required this.remoteSrc,
+    required this.remoteSrc,
     this.shouldCheckCache = false,
   });
 
   /// Return the cached results of listing a directory [f]
   ///
   /// Should check [isGood] before using the cache returning by this method
-  Future<List<File>> list(Account account, File f) async {
+  Future<List<File>?> list(Account account, File f) async {
     final trimmedRootPath = f.path.trimAny("/");
-    List<File> cache;
+    List<File>? cache;
     try {
       cache = await appDbSrc.list(account, f);
       // compare the cached root
@@ -645,7 +644,7 @@ class _CacheManager {
   }
 
   bool get isGood => _isGood;
-  String get remoteTouchToken => _remoteToken;
+  String? get remoteTouchToken => _remoteToken;
 
   Future<void> _checkTouchToken(
       Account account, File f, List<File> cache) async {
@@ -653,7 +652,7 @@ class _CacheManager {
         "${remote_storage_util.getRemoteTouchDir(account)}/${f.strippedPath}";
     final fileRepo = FileRepo(FileCachedDataSource());
     final tokenManager = TouchTokenManager();
-    String remoteToken;
+    String? remoteToken;
     try {
       remoteToken = await tokenManager.getRemoteToken(fileRepo, account, f);
     } catch (e, stacktrace) {
@@ -664,7 +663,7 @@ class _CacheManager {
     }
     _remoteToken = remoteToken;
 
-    String localToken;
+    String? localToken;
     try {
       localToken = await tokenManager.getLocalToken(account, f);
     } catch (e, stacktrace) {
@@ -687,7 +686,7 @@ class _CacheManager {
   final bool shouldCheckCache;
 
   var _isGood = false;
-  String _remoteToken;
+  String? _remoteToken;
 
   static final _log = Logger("entity.file.data_source._CacheManager");
 }

lib/entity/webdav_response_parser.dart

@@ -31,7 +31,7 @@ class WebdavFileParser {
             return null;
           }
         })
-        .where((element) => element != null)
+        .whereType<File>()
         .toList();
   }
 
@@ -55,19 +55,19 @@ class WebdavFileParser {
 
   /// Map <DAV:response> contents to File
   File _toFile(XmlElement element) {
-    String path;
+    String? path;
-    int contentLength;
+    int? contentLength;
-    String contentType;
+    String? contentType;
-    String etag;
+    String? etag;
-    DateTime lastModified;
+    DateTime? lastModified;
-    bool isCollection;
+    bool? isCollection;
-    int usedBytes;
+    int? usedBytes;
-    bool hasPreview;
+    bool? hasPreview;
-    int fileId;
+    int? fileId;
-    String ownerId;
+    String? ownerId;
-    Metadata metadata;
+    Metadata? metadata;
-    bool isArchived;
+    bool? isArchived;
-    DateTime overrideDateTime;
+    DateTime? overrideDateTime;
 
     for (final child in element.children.whereType<XmlElement>()) {
       if (child.matchQualifiedName("href",
@@ -105,7 +105,7 @@ class WebdavFileParser {
     }
 
     return File(
-      path: path,
+      path: path!,
       contentLength: contentLength,
       contentType: contentType,
       etag: etag,
@@ -140,7 +140,10 @@ class WebdavFileParser {
 }
 
 class _PropParser {
-  _PropParser({this.namespaces = const {}, this.logFilePath});
+  _PropParser({
+    this.namespaces = const {},
+    this.logFilePath,
+  });
 
   /// Parse <DAV:prop> element contents
   void parse(XmlElement element) {
@@ -201,43 +204,43 @@ class _PropParser {
     }
   }
 
-  DateTime get lastModified => _lastModified;
+  DateTime? get lastModified => _lastModified;
-  int get contentLength => _contentLength;
+  int? get contentLength => _contentLength;
-  String get contentType => _contentType;
+  String? get contentType => _contentType;
-  String get etag => _etag;
+  String? get etag => _etag;
-  int get usedBytes => _usedBytes;
+  int? get usedBytes => _usedBytes;
-  bool get isCollection => _isCollection;
+  bool? get isCollection => _isCollection;
-  bool get hasPreview => _hasPreview;
+  bool? get hasPreview => _hasPreview;
-  int get fileId => _fileId;
+  int? get fileId => _fileId;
-  String get ownerId => _ownerId;
+  String? get ownerId => _ownerId;
-  Metadata get metadata => _metadata;
+  Metadata? get metadata => _metadata;
-  bool get isArchived => _isArchived;
+  bool? get isArchived => _isArchived;
-  DateTime get overrideDateTime => _overrideDateTime;
+  DateTime? get overrideDateTime => _overrideDateTime;
 
   final Map<String, String> namespaces;
 
   /// File path for logging only
-  final String logFilePath;
+  final String? logFilePath;
 
-  DateTime _lastModified;
+  DateTime? _lastModified;
-  int _contentLength;
+  int? _contentLength;
-  String _contentType;
+  String? _contentType;
-  String _etag;
+  String? _etag;
-  int _usedBytes;
+  int? _usedBytes;
-  bool _isCollection;
+  bool? _isCollection;
-  bool _hasPreview;
+  bool? _hasPreview;
-  int _fileId;
+  int? _fileId;
-  String _ownerId;
+  String? _ownerId;
-  Metadata _metadata;
+  Metadata? _metadata;
-  bool _isArchived;
+  bool? _isArchived;
-  DateTime _overrideDateTime;
+  DateTime? _overrideDateTime;
 }
 
 extension on XmlElement {
   bool matchQualifiedName(
     String local, {
-    String prefix,
+    required String prefix,
-    Map<String, String> namespaces,
+    required Map<String, String> namespaces,
   }) {
     final localNamespaces = <String, String>{};
     for (final a in attributes) {

lib/event/event.dart

@@ -23,13 +23,13 @@ class AppEventListener<T> {
       _log.warning("[endListenEvent] Already not listening");
       return;
     }
-    _subscription.cancel();
+    _subscription?.cancel();
     _subscription = null;
   }
 
   final void Function(T) _listener;
   final _stream = KiwiContainer().resolve<EventBus>().on<T>();
-  StreamSubscription<T> _subscription;
+  StreamSubscription<T>? _subscription;
 
   final _log = Logger("event.event.AppEventListener<${T.runtimeType}>");
 }

lib/exception.dart

@@ -16,7 +16,10 @@ class CacheNotFoundException implements Exception {
 }
 
 class ApiException implements Exception {
-  ApiException({this.response, this.message});
+  ApiException({
+    required this.response,
+    this.message,
+  });
 
   @override
   toString() {

lib/exception_util.dart

@@ -10,16 +10,16 @@ import 'package:nc_photos/exception.dart';
 String toUserString(dynamic exception, BuildContext context) {
   if (exception is ApiException) {
     if (exception.response.statusCode == 401) {
-      return AppLocalizations.of(context).errorUnauthenticated;
+      return AppLocalizations.of(context)!.errorUnauthenticated;
     } else if (exception.response.statusCode == 423) {
-      return AppLocalizations.of(context).errorLocked;
+      return AppLocalizations.of(context)!.errorLocked;
     } else if (exception.response.statusCode == 500) {
-      return AppLocalizations.of(context).errorServerError;
+      return AppLocalizations.of(context)!.errorServerError;
     }
   } else if (exception is SocketException) {
-    return AppLocalizations.of(context).errorDisconnected;
+    return AppLocalizations.of(context)!.errorDisconnected;
   } else if (exception is InvalidBaseUrlException) {
-    return AppLocalizations.of(context).errorInvalidBaseUrl;
+    return AppLocalizations.of(context)!.errorInvalidBaseUrl;
   }
   return exception.toString();
 }

lib/iterable_extension.dart

@@ -3,10 +3,10 @@ import 'package:tuple/tuple.dart';
 
 extension IterableExtension<T> on Iterable<T> {
   /// Return a new sorted list
-  List<T> sorted([int compare(T a, T b)]) => this.toList()..sort(compare);
+  List<T> sorted([int compare(T a, T b)?]) => this.toList()..sort(compare);
 
   /// Return a new stable sorted list
-  List<T> stableSorted([int compare(T a, T b)]) {
+  List<T> stableSorted([int compare(T a, T b)?]) {
     final tmp = this.toList();
     mergeSort(tmp, compare: compare);
     return tmp;

lib/language_util.dart

@@ -6,12 +6,12 @@ class AppLanguage {
 
   final int langId;
   final String nativeName;
-  final Locale locale;
+  final Locale? locale;
 }
 
 String getSelectedLanguageName(BuildContext context) =>
     _getSelectedLanguage(context).nativeName;
-Locale getSelectedLocale(BuildContext context) =>
+Locale? getSelectedLocale(BuildContext context) =>
     _getSelectedLanguage(context).locale;
 
 final supportedLanguages = {
@@ -32,9 +32,9 @@ enum _AppLanguageEnum {
 
 AppLanguage _getSelectedLanguage(BuildContext context) {
   try {
-    final lang = Pref.inst().getLanguage();
+    final lang = Pref.inst().getLanguageOr(0);
-    return supportedLanguages[lang];
+    return supportedLanguages[lang]!;
   } catch (_) {
-    return supportedLanguages[_AppLanguageEnum.systemDefault.index];
+    return supportedLanguages[_AppLanguageEnum.systemDefault.index]!;
   }
 }

lib/main.dart

@@ -72,8 +72,8 @@ void _initLog() {
 
 Future<void> _initPref() async {
   await Pref.init();
-  if (Pref.inst().getLastVersion(null) == null) {
+  if (Pref.inst().getLastVersion() == null) {
-    if (Pref.inst().getSetupProgress(null) == null) {
+    if (Pref.inst().getSetupProgress() == null) {
       // new install
       await Pref.inst().setLastVersion(k.version);
     } else {

lib/metadata_task_manager.dart

@@ -25,7 +25,7 @@ class MetadataTask {
       final op = UpdateMissingMetadata(fileRepo);
       await for (final _ in op(account,
           File(path: "${api_util.getWebdavRootUrlRelative(account)}/$r"))) {
-        if (!Pref.inst().isEnableExif()) {
+        if (!Pref.inst().isEnableExifOr()) {
           _log.info("[call] EXIF disabled, task ending immaturely");
           op.stop();
           return;
@@ -53,7 +53,7 @@ class MetadataTaskManager {
 
   void _handleStream() async {
     await for (final task in _streamController.stream) {
-      if (Pref.inst().isEnableExif()) {
+      if (Pref.inst().isEnableExifOr()) {
         _log.info("[_doTask] Executing task: $task");
         await task();
       } else {

lib/mobile/android/media_store.dart

@@ -6,11 +6,13 @@ class MediaStore {
   static const exceptionCodePermissionError = "permissionError";
 
   static Future<String> saveFileToDownload(
-          String fileName, Uint8List fileContent) =>
+      String fileName, Uint8List fileContent) async {
-      _channel.invokeMethod("saveFileToDownload", <String, dynamic>{
+    return (await _channel
-        "fileName": fileName,
+        .invokeMethod<String>("saveFileToDownload", <String, dynamic>{
-        "content": fileContent,
+      "fileName": fileName,
-      });
+      "content": fileContent,
+    }))!;
+  }
 
   static const _channel =
       const MethodChannel("com.nkming.nc_photos/media_store");

lib/mobile/android/notification.dart

@@ -2,7 +2,7 @@ import 'package:flutter/services.dart';
 
 class Notification {
   static Future<void> notifyItemsDownloadSuccessful(
-          List<String> fileUris, List<String> mimeTypes) =>
+          List<String> fileUris, List<String?> mimeTypes) =>
       _channel.invokeMethod("notifyItemsDownloadSuccessful", <String, dynamic>{
         "fileUris": fileUris,
         "mimeTypes": mimeTypes,

lib/mobile/android/share.dart

@@ -2,7 +2,7 @@ import 'package:flutter/services.dart';
 
 class Share {
   static Future<void> shareItems(
-          List<String> fileUris, List<String> mimeTypes) =>
+          List<String> fileUris, List<String?> mimeTypes) =>
       _channel.invokeMethod("shareItems", <String, dynamic>{
         "fileUris": fileUris,
         "mimeTypes": mimeTypes,

lib/mobile/map_widget.dart

@@ -4,9 +4,9 @@ import 'package:tuple/tuple.dart';
 
 class Map extends StatelessWidget {
   const Map({
-    Key key,
+    Key? key,
-    this.center,
+    required this.center,
-    this.zoom,
+    required this.zoom,
     this.onTap,
   }) : super(key: key);
 
@@ -44,5 +44,5 @@ class Map extends StatelessWidget {
   /// A pair of latitude and longitude coordinates, stored as degrees
   final Tuple2<double, double> center;
   final double zoom;
-  final void Function() onTap;
+  final VoidCallback? onTap;
 }

lib/mobile/notification.dart

@@ -11,5 +11,5 @@ class AndroidItemDownloadSuccessfulNotification
   }
 
   final List<String> fileUris;
-  final List<String> mimeTypes;
+  final List<String?> mimeTypes;
 }

lib/mobile/self_signed_cert_manager.dart

@@ -103,7 +103,7 @@ class SelfSignedCertManager {
     }
   }
 
-  _BadCertInfo _latestBadCert;
+  late _BadCertInfo _latestBadCert;
   var _whitelist = <_CertInfo>[];
 
   static SelfSignedCertManager _inst = SelfSignedCertManager._();
@@ -168,7 +168,7 @@ class _BadCertInfo {
 
 class _CustomHttpOverrides extends HttpOverrides {
   @override
-  HttpClient createHttpClient(SecurityContext context) {
+  HttpClient createHttpClient(SecurityContext? context) {
     return super.createHttpClient(context)
       ..badCertificateCallback = (cert, host, port) {
         try {

lib/mobile/share.dart

@@ -10,5 +10,5 @@ class AndroidShare extends itf.Share {
   }
 
   final List<String> fileUris;
-  final List<String> mimeTypes;
+  final List<String?> mimeTypes;
 }

lib/or_null.dart

@@ -2,7 +2,9 @@
 class OrNull<T> {
   OrNull(this.obj);
 
-  static bool isNull(OrNull x) => x != null && x.obj == null;
+  /// Return iff the value of [x] is set to null, which means if [x] itself is
+  /// null, false will still be returned
+  static bool isSetNull(OrNull? x) => x != null && x.obj == null;
 
-  final T obj;
+  final T? obj;
 }

lib/platform/universal_storage.dart

@@ -9,13 +9,13 @@ abstract class UniversalStorage {
 
   /// Return the content associated with [name], or null if no such association
   /// exists
-  Future<Uint8List> getBinary(String name);
+  Future<Uint8List?> getBinary(String name);
 
   Future<void> putString(String name, String content);
 
   /// Return the string associated with [name], or null if no such association
   /// exists
-  Future<String> getString(String name);
+  Future<String?> getString(String name);
 
   Future<void> remove(String name);
 }

lib/pref.dart

@@ -12,67 +12,65 @@ class Pref {
 
   factory Pref.inst() => _inst;
 
-  List<Account> getAccounts([List<Account> def]) {
+  List<Account>? getAccounts() {
     final jsonObjs = _pref.getStringList("accounts");
-    return jsonObjs?.map((e) => Account.fromJson(jsonDecode(e)))?.toList() ??
+    return jsonObjs?.map((e) => Account.fromJson(jsonDecode(e))).toList();
-        def;
   }
 
+  List<Account> getAccountsOr(List<Account> def) => getAccounts() ?? def;
   Future<bool> setAccounts(List<Account> value) {
     final jsons = value.map((e) => jsonEncode(e.toJson())).toList();
     return _pref.setStringList("accounts", jsons);
   }
 
-  int getCurrentAccountIndex([int def]) =>
+  int? getCurrentAccountIndex() => _pref.getInt("currentAccountIndex");
-      _pref.getInt("currentAccountIndex") ?? def;
+  int getCurrentAccountIndexOr(int def) => getCurrentAccountIndex() ?? def;
-
   Future<bool> setCurrentAccountIndex(int value) =>
       _pref.setInt("currentAccountIndex", value);
 
-  int getHomePhotosZoomLevel([int def]) =>
+  int? getHomePhotosZoomLevel() => _pref.getInt("homePhotosZoomLevel");
-      _pref.getInt("homePhotosZoomLevel") ?? def;
+  int getHomePhotosZoomLevelOr(int def) => getHomePhotosZoomLevel() ?? def;
-
   Future<bool> setHomePhotosZoomLevel(int value) =>
       _pref.setInt("homePhotosZoomLevel", value);
 
-  int getAlbumViewerZoomLevel([int def]) =>
+  int? getAlbumViewerZoomLevel() => _pref.getInt("albumViewerZoomLevel");
-      _pref.getInt("albumViewerZoomLevel") ?? def;
+  int getAlbumViewerZoomLevelOr(int def) => getAlbumViewerZoomLevel() ?? def;
-
   Future<bool> setAlbumViewerZoomLevel(int value) =>
       _pref.setInt("albumViewerZoomLevel", value);
 
-  bool isEnableExif([bool def = true]) => _pref.getBool("isEnableExif") ?? def;
+  bool? isEnableExif() => _pref.getBool("isEnableExif");
-
+  bool isEnableExifOr([bool def = true]) => isEnableExif() ?? def;
   Future<bool> setEnableExif(bool value) =>
       _pref.setBool("isEnableExif", value);
 
-  int getSetupProgress([int def = 0]) => _pref.getInt("setupProgress") ?? def;
+  int? getSetupProgress() => _pref.getInt("setupProgress");
-
+  int getSetupProgressOr([int def = 0]) => getSetupProgress() ?? def;
   Future<bool> setSetupProgress(int value) =>
       _pref.setInt("setupProgress", value);
 
   /// Return the version number when the app last ran
-  int getLastVersion([int def = 0]) => _pref.getInt("lastVersion") ?? def;
+  int? getLastVersion() => _pref.getInt("lastVersion");
-
+  int getLastVersionOr(int def) => getLastVersion() ?? def;
   Future<bool> setLastVersion(int value) => _pref.setInt("lastVersion", value);
 
-  bool isDarkTheme([bool def = false]) => _pref.getBool("isDarkTheme") ?? def;
+  bool? isDarkTheme() => _pref.getBool("isDarkTheme");
-
+  bool isDarkThemeOr(bool def) => isDarkTheme() ?? def;
   Future<bool> setDarkTheme(bool value) => _pref.setBool("isDarkTheme", value);
 
-  int getLanguage([int def = 0]) => _pref.getInt("language") ?? def;
+  int? getLanguage() => _pref.getInt("language");
+  int getLanguageOr(int def) => getLanguage() ?? def;
   Future<bool> setLanguage(int value) => _pref.setInt("language", value);
 
   Pref._();
 
   static final _inst = Pref._();
-  SharedPreferences _pref;
+  late SharedPreferences _pref;
 }
 
 extension PrefExtension on Pref {
-  Account getCurrentAccount() {
+  Account? getCurrentAccount() {
     try {
-      return Pref.inst().getAccounts()[Pref.inst().getCurrentAccountIndex()];
+      return Pref.inst().getAccounts()![Pref.inst().getCurrentAccountIndex()!];
     } catch (_) {
       return null;
     }

lib/share_handler.dart

@@ -23,7 +23,7 @@ class ShareHandler {
     showDialog(
       context: context,
       builder: (context) => ProcessingDialog(
-          text: AppLocalizations.of(context).shareDownloadingDialogContent),
+          text: AppLocalizations.of(context)!.shareDownloadingDialogContent),
     );
     final results = <Tuple2<File, dynamic>>[];
     for (final f in files) {
@@ -33,7 +33,7 @@ class ShareHandler {
       } on PermissionException catch (_) {
         _log.warning("[shareFiles] Permission not granted");
         SnackBarManager().showSnackBar(SnackBar(
-          content: Text(AppLocalizations.of(context)
+          content: Text(AppLocalizations.of(context)!
               .downloadFailureNoPermissionNotification),
           duration: k.snackBarDurationNormal,
         ));

lib/snack_bar_manager.dart

@@ -22,7 +22,7 @@ class SnackBarManager {
   /// Show a snack bar if possible
   ///
   /// If the snack bar can't be shown at this time, return null
-  ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showSnackBar(
+  ScaffoldFeatureController<SnackBar, SnackBarClosedReason>? showSnackBar(
       SnackBar snackBar) {
     for (final h in _handlers.reversed) {
       final result = h.showSnackBar(snackBar);
@@ -42,6 +42,6 @@ class SnackBarManager {
 }
 
 abstract class SnackBarHandler {
-  ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showSnackBar(
+  ScaffoldFeatureController<SnackBar, SnackBarClosedReason>? showSnackBar(
       SnackBar snackBar);
 }

lib/theme.dart

@@ -2,7 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
 class AppTheme extends StatelessWidget {
-  const AppTheme({@required this.child});
+  const AppTheme({
+    required this.child,
+  });
 
   @override
   Widget build(BuildContext context) {
@@ -46,24 +48,24 @@ class AppTheme extends StatelessWidget {
 
   static Color getSelectionOverlayColor(BuildContext context) {
     return Theme.of(context).brightness == Brightness.light
-        ? primarySwatchLight[100].withOpacity(0.7)
+        ? primarySwatchLight[100]!.withOpacity(0.7)
-        : primarySwatchDark[700].withOpacity(0.7);
+        : primarySwatchDark[700]!.withOpacity(0.7);
   }
 
   static Color getSelectionCheckColor(BuildContext context) {
     return Theme.of(context).brightness == Brightness.light
-        ? Colors.grey[800]
+        ? Colors.grey[800]!
-        : Colors.grey[350];
+        : Colors.grey[350]!;
   }
 
   static Color getOverscrollIndicatorColor(BuildContext context) {
     return Theme.of(context).brightness == Brightness.light
-        ? Colors.grey[800]
+        ? Colors.grey[800]!
-        : Colors.grey[200];
+        : Colors.grey[200]!;
   }
 
   static Color getRootPickerContentBoxColor(BuildContext context) {
-    return Colors.blue[200];
+    return Colors.blue[200]!;
   }
 
   static Color getPrimaryTextColor(BuildContext context) {

lib/touch_token_manager.dart

@@ -21,7 +21,7 @@ import 'package:nc_photos/use_case/remove.dart';
 /// doing it on every query
 class TouchTokenManager {
   Future<void> setRemoteToken(
-      FileRepo fileRepo, Account account, File file, String token) async {
+      FileRepo fileRepo, Account account, File file, String? token) async {
     _log.info(
         "[setRemoteToken] Set remote token for file '${file.path}': $token");
     final path = _getRemotePath(account, file);
@@ -36,7 +36,7 @@ class TouchTokenManager {
 
   /// Return the touch token for [file] from remote source, or null if no such
   /// file
-  Future<String> getRemoteToken(
+  Future<String?> getRemoteToken(
       FileRepo fileRepo, Account account, File file) async {
     final path = _getRemotePath(account, file);
     try {
@@ -51,7 +51,7 @@ class TouchTokenManager {
     }
   }
 
-  Future<void> setLocalToken(Account account, File file, String token) {
+  Future<void> setLocalToken(Account account, File file, String? token) {
     _log.info(
         "[setLocalToken] Set local token for file '${file.path}': $token");
     final name = _getLocalStorageName(account, file);
@@ -62,7 +62,7 @@ class TouchTokenManager {
     }
   }
 
-  Future<String> getLocalToken(Account account, File file) async {
+  Future<String?> getLocalToken(Account account, File file) async {
     final name = _getLocalStorageName(account, file);
     return platform.UniversalStorage().getString(name);
   }

lib/use_case/load_metadata.dart

@@ -22,9 +22,9 @@ class LoadMetadata {
   }
 
   Future<Map<String, dynamic>> _loadMetadata({
-    @required File file,
+    required File file,
-    exifdart.AbstractBlobReader Function() exifdartReaderBuilder,
+    required exifdart.AbstractBlobReader Function() exifdartReaderBuilder,
-    AsyncImageInput Function() imageSizeGetterInputBuilder,
+    required AsyncImageInput Function() imageSizeGetterInputBuilder,
   }) async {
     var metadata = exifdart.Metadata();
     if (file_util.isMetadataSupportedFormat(file)) {
@@ -47,8 +47,8 @@ class LoadMetadata {
             await AsyncImageSizeGetter.getSize(imageSizeGetterInputBuilder());
         // image size getter doesn't handle exif orientation
         if (metadata.exif?.containsKey("Orientation") == true &&
-            metadata.exif["Orientation"] >= 5 &&
+            metadata.exif!["Orientation"] >= 5 &&
-            metadata.exif["Orientation"] <= 8) {
+            metadata.exif!["Orientation"] <= 8) {
           // 90 deg CW/CCW
           imageWidth = resolution.height;
           imageHeight = resolution.width;
@@ -66,12 +66,12 @@ class LoadMetadata {
       }
     } else {
       if (metadata.rotateAngleCcw != null &&
-          metadata.rotateAngleCcw % 180 != 0) {
+          metadata.rotateAngleCcw! % 180 != 0) {
-        imageWidth = metadata.imageHeight;
+        imageWidth = metadata.imageHeight!;
-        imageHeight = metadata.imageWidth;
+        imageHeight = metadata.imageWidth!;
       } else {
-        imageWidth = metadata.imageWidth;
+        imageWidth = metadata.imageWidth!;
-        imageHeight = metadata.imageHeight;
+        imageHeight = metadata.imageHeight!;
       }
     }
 

lib/use_case/remove.dart

@@ -24,6 +24,7 @@ class Remove {
   }
 
   Future<void> _cleanUpAlbums(Account account, File file) async {
+    final albumRepo = this.albumRepo!;
     final albums = (await ListAlbum(fileRepo, albumRepo)(account)
         .where((event) => event is Album)
         .toList()).cast<Album>();
@@ -58,7 +59,7 @@ class Remove {
   }
 
   final FileRepo fileRepo;
-  final AlbumRepo albumRepo;
+  final AlbumRepo? albumRepo;
 
   static final _log = Logger("use_case.remove.Remove");
 }

lib/use_case/resync_album.dart

@@ -44,18 +44,22 @@ class ResyncAlbum {
 
   Future<AlbumFileItem> _syncOne(Account account, AlbumFileItem item,
       ObjectStore objStore, Index index) async {
-    Map dbItem;
+    Map? dbItem;
     if (item.file.fileId != null) {
       final List dbItems = await index
           .getAll(AppDbFileDbEntry.toNamespacedFileId(account, item.file));
       // find the one owned by us
-      dbItem = dbItems.firstWhere((element) {
+      try {
-        final e = AppDbFileDbEntry.fromJson(element.cast<String, dynamic>());
+        dbItem = dbItems.firstWhere((element) {
-        return file_util.getUserDirName(e.file) == account.username;
+          final e = AppDbFileDbEntry.fromJson(element.cast<String, dynamic>());
-      }, orElse: () => null);
+          return file_util.getUserDirName(e.file) == account.username;
+        });
+      } on StateError catch (_) {
+        // not found
+      }
     } else {
       dbItem = await objStore
-          .getObject(AppDbFileDbEntry.toPrimaryKey(account, item.file));
+          .getObject(AppDbFileDbEntry.toPrimaryKey(account, item.file)) as Map;
     }
     if (dbItem == null) {
       _log.warning(

lib/use_case/update_dynamic_album_cover.dart

@@ -40,8 +40,9 @@ class UpdateDynamicAlbumCover {
   }
 
   Album _updateWithSortedFiles(Album album, List<File> sortedFiles) {
-    final coverFile = sortedFiles.firstWhere((element) => element.hasPreview);
+    try {
-    if (coverFile != null) {
+      final coverFile =
+          sortedFiles.firstWhere((element) => element.hasPreview ?? false);
       // cache the result for later use
       if (coverFile.path !=
           (album.coverProvider as AlbumAutoCoverProvider).coverFile?.path) {
@@ -51,6 +52,8 @@ class UpdateDynamicAlbumCover {
           ),
         );
       }
+    } on StateError catch (_) {
+      // no files
     }
     return album;
   }

lib/use_case/update_dynamic_album_time.dart

@@ -37,7 +37,7 @@ class UpdateDynamicAlbumTime {
   }
 
   Album _updateWithSortedFiles(Album album, List<File> sortedFiles) {
-    DateTime latestItemTime;
+    DateTime? latestItemTime;
     try {
       latestItemTime = sortedFiles.first.bestDateTime;
     } catch (_) {

lib/use_case/update_missing_metadata.dart

@@ -40,8 +40,8 @@ class UpdateMissingMetadata {
         _log.fine("[call] Updating metadata for ${file.path}");
         final binary = await GetFileBinary(fileRepo)(account, file);
         final metadata = await LoadMetadata()(account, file, binary);
-        int imageWidth, imageHeight;
+        int? imageWidth, imageHeight;
-        Exif exif;
+        Exif? exif;
         if (metadata.containsKey("resolution")) {
           imageWidth = metadata["resolution"]["width"];
           imageHeight = metadata["resolution"]["height"];

lib/use_case/update_property.dart

@@ -12,9 +12,9 @@ class UpdateProperty {
   Future<void> call(
     Account account,
     File file, {
-    OrNull<Metadata> metadata,
+    OrNull<Metadata>? metadata,
-    OrNull<bool> isArchived,
+    OrNull<bool>? isArchived,
-    OrNull<DateTime> overrideDateTime,
+    OrNull<DateTime>? overrideDateTime,
   }) async {
     if (metadata == null && isArchived == null && overrideDateTime == null) {
       // ?
@@ -22,9 +22,9 @@ class UpdateProperty {
       return;
     }
 
-    if (metadata?.obj != null && metadata.obj.fileEtag != file.etag) {
+    if (metadata?.obj != null && metadata!.obj!.fileEtag != file.etag) {
       _log.warning(
-          "[call] Metadata fileEtag mismatch with actual file's (metadata: ${metadata.obj.fileEtag}, file: ${file.etag})");
+          "[call] Metadata fileEtag mismatch with actual file's (metadata: ${metadata.obj!.fileEtag}, file: ${file.etag})");
     }
     await fileRepo.updateProperty(
       account,

lib/web/db_util.dart

@@ -1,4 +1,4 @@
 import 'package:idb_shim/idb_browser.dart';
 import 'package:idb_shim/idb_shim.dart';
 
-IdbFactory getDbFactory() => getIdbFactory();
+IdbFactory getDbFactory() => idbFactoryBrowser;

lib/web/map_widget.dart

@@ -8,9 +8,9 @@ import 'package:tuple/tuple.dart';
 
 class Map extends StatefulWidget {
   const Map({
-    Key key,
+    Key? key,
-    this.center,
+    required this.center,
-    this.zoom,
+    required this.zoom,
     this.onTap,
   }) : super(key: key);
 
@@ -20,7 +20,7 @@ class Map extends StatefulWidget {
   /// A pair of latitude and longitude coordinates, stored as degrees
   final Tuple2<double, double> center;
   final double zoom;
-  final void Function() onTap;
+  final void Function()? onTap;
 }
 
 class _MapState extends State<Map> {

lib/widget/account_picker_dialog.dart

@@ -15,8 +15,8 @@ import 'package:nc_photos/widget/sign_in.dart';
 /// A dialog that allows the user to switch between accounts
 class AccountPickerDialog extends StatefulWidget {
   AccountPickerDialog({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
   @override
@@ -29,7 +29,7 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
   @override
   initState() {
     super.initState();
-    _accounts = Pref.inst().getAccounts([]);
+    _accounts = Pref.inst().getAccountsOr([]);
   }
 
   @override
@@ -48,7 +48,7 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
                     Icons.close,
                     color: AppTheme.getSecondaryTextColor(context),
                   ),
-                  tooltip: AppLocalizations.of(context).deleteTooltip,
+                  tooltip: AppLocalizations.of(context)!.deleteTooltip,
                   onPressed: () => _onRemoveItemPressed(a),
                 ),
               ),
@@ -63,7 +63,7 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
             ..pushNamed(SignIn.routeName);
         },
         child: Tooltip(
-          message: AppLocalizations.of(context).addServerTooltip,
+          message: AppLocalizations.of(context)!.addServerTooltip,
           child: Center(
             child: Icon(
               Icons.add,
@@ -89,7 +89,7 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
             Icons.edit,
             color: AppTheme.getSecondaryTextColor(context),
           ),
-          tooltip: AppLocalizations.of(context).editTooltip,
+          tooltip: AppLocalizations.of(context)!.editTooltip,
           onPressed: () => _onEditPressed(),
         ),
       ),
@@ -106,20 +106,28 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
   }
 
   void _onRemoveItemPressed(Account account) {
-    _removeAccount(account);
+    try {
-    setState(() {
+      _removeAccount(account);
-      _accounts = Pref.inst().getAccounts([]);
+      setState(() {
-    });
+        _accounts = Pref.inst().getAccounts()!;
-    SnackBarManager().showSnackBar(SnackBar(
+      });
-      content: Text(AppLocalizations.of(context)
+      SnackBarManager().showSnackBar(SnackBar(
-          .removeServerSuccessNotification(account.url)),
+        content: Text(AppLocalizations.of(context)!
-      duration: k.snackBarDurationNormal,
+            .removeServerSuccessNotification(account.url)),
-    ));
+        duration: k.snackBarDurationNormal,
+      ));
+    } catch (e) {
+      SnackBarManager().showSnackBar(SnackBar(
+        content: Text(exception_util.toUserString(e, context)),
+        duration: k.snackBarDurationNormal,
+      ));
+    }
   }
 
   void _onEditPressed() async {
     try {
-      final result = await Navigator.of(context).pushNamed(RootPicker.routeName,
+      final result = await Navigator.of(context).pushNamed<Account>(
+          RootPicker.routeName,
           arguments: RootPickerArguments(widget.account));
       if (result != null) {
         // we've got a good account
@@ -129,19 +137,19 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
           Navigator.of(context).pop();
           return;
         }
-        final accounts = Pref.inst().getAccounts([]);
+        final accounts = Pref.inst().getAccounts()!;
         if (accounts.contains(result)) {
           // conflict with another account. This normally won't happen because
           // the app passwords are unique to each entry, but just in case
           Navigator.of(context).pop();
           SnackBarManager().showSnackBar(SnackBar(
-            content: Text(AppLocalizations.of(context)
+            content: Text(AppLocalizations.of(context)!
                 .editAccountConflictFailureNotification),
             duration: k.snackBarDurationNormal,
           ));
           return;
         }
-        accounts[Pref.inst().getCurrentAccountIndex()] = result;
+        accounts[Pref.inst().getCurrentAccountIndex()!] = result;
         Pref.inst()..setAccounts(accounts);
         Navigator.pushNamedAndRemoveUntil(
             context, Home.routeName, (route) => false,
@@ -158,9 +166,9 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
   }
 
   void _removeAccount(Account account) {
-    final currentAccounts = Pref.inst().getAccounts([]);
+    final currentAccounts = Pref.inst().getAccounts()!;
     final currentAccount =
-        currentAccounts[Pref.inst().getCurrentAccountIndex()];
+        currentAccounts[Pref.inst().getCurrentAccountIndex()!];
     final newAccounts =
         currentAccounts.where((element) => element != account).toList();
     final newAccountIndex = newAccounts.indexOf(currentAccount);
@@ -172,7 +180,7 @@ class _AccountPickerDialogState extends State<AccountPickerDialog> {
       ..setCurrentAccountIndex(newAccountIndex);
   }
 
-  List<Account> _accounts;
+  late List<Account> _accounts;
 
   static final _log =
       Logger("widget.account_picker_dialog._AccountPickerDialogState");

lib/widget/album_dir_picker.dart

@@ -21,12 +21,17 @@ class AlbumDirPickerArguments {
 class AlbumDirPicker extends StatefulWidget {
   static const routeName = "/album-dir-picker";
 
+  static Route buildRoute(AlbumDirPickerArguments args) =>
+      MaterialPageRoute<List<File>>(
+        builder: (context) => AlbumDirPicker.fromArgs(args),
+      );
+
   AlbumDirPicker({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  AlbumDirPicker.fromArgs(AlbumDirPickerArguments args, {Key key})
+  AlbumDirPicker.fromArgs(AlbumDirPickerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -81,7 +86,7 @@ class _AlbumDirPickerState extends State<AlbumDirPicker>
             child: Column(
               children: [
                 Text(
-                  AppLocalizations.of(context).albumDirPickerHeaderText,
+                  AppLocalizations.of(context)!.albumDirPickerHeaderText,
                   style: Theme.of(context).textTheme.headline5,
                   textAlign: TextAlign.center,
                 ),
@@ -89,7 +94,7 @@ class _AlbumDirPickerState extends State<AlbumDirPicker>
                 Align(
                   alignment: AlignmentDirectional.topStart,
                   child: Text(
-                    AppLocalizations.of(context).albumDirPickerSubHeaderText,
+                    AppLocalizations.of(context)!.albumDirPickerSubHeaderText,
                   ),
                 ),
               ],
@@ -112,7 +117,7 @@ class _AlbumDirPickerState extends State<AlbumDirPicker>
                 ),
                 ElevatedButton(
                   onPressed: () => _onConfirmPressed(context),
-                  child: Text(AppLocalizations.of(context).confirmButtonLabel),
+                  child: Text(AppLocalizations.of(context)!.confirmButtonLabel),
                 ),
               ],
             ),
@@ -127,7 +132,7 @@ class _AlbumDirPickerState extends State<AlbumDirPicker>
     if (picked.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).albumDirPickerListEmptyNotification),
+            AppLocalizations.of(context)!.albumDirPickerListEmptyNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {

lib/widget/album_grid_item.dart

@@ -5,9 +5,9 @@ import 'package:nc_photos/widget/selectable.dart';
 
 class AlbumGridItem extends StatelessWidget {
   AlbumGridItem({
-    Key key,
+    Key? key,
-    @required this.cover,
+    required this.cover,
-    @required this.title,
+    required this.title,
     this.subtitle,
     this.subtitle2,
     this.icon,
@@ -50,8 +50,8 @@ class AlbumGridItem extends StatelessWidget {
             ),
             const SizedBox(height: 8),
             Text(
-              title ?? "",
+              title,
-              style: Theme.of(context).textTheme.bodyText1.copyWith(
+              style: Theme.of(context).textTheme.bodyText1!.copyWith(
                     color: AppTheme.getPrimaryTextColor(context),
                   ),
               textAlign: TextAlign.start,
@@ -64,7 +64,7 @@ class AlbumGridItem extends StatelessWidget {
                 Expanded(
                   child: Text(
                     subtitle ?? "",
-                    style: Theme.of(context).textTheme.bodyText2.copyWith(
+                    style: Theme.of(context).textTheme.bodyText2!.copyWith(
                           fontSize: 10,
                           color: AppTheme.getSecondaryTextColor(context),
                         ),
@@ -75,8 +75,8 @@ class AlbumGridItem extends StatelessWidget {
                 ),
                 if (subtitle2?.isNotEmpty == true)
                   Text(
-                    subtitle2,
+                    subtitle2!,
-                    style: Theme.of(context).textTheme.bodyText2.copyWith(
+                    style: Theme.of(context).textTheme.bodyText2!.copyWith(
                           fontSize: 10,
                           color: AppTheme.getSecondaryTextColor(context),
                         ),
@@ -93,12 +93,12 @@ class AlbumGridItem extends StatelessWidget {
 
   final Widget cover;
   final String title;
-  final String subtitle;
+  final String? subtitle;
 
   /// Appears after [subtitle], aligned to the end side of parent
-  final String subtitle2;
+  final String? subtitle2;
-  final IconData icon;
+  final IconData? icon;
   final bool isSelected;
-  final VoidCallback onTap;
+  final VoidCallback? onTap;
-  final VoidCallback onLongPress;
+  final VoidCallback? onLongPress;
 }

lib/widget/album_importer.dart

@@ -34,12 +34,16 @@ class AlbumImporterArguments {
 class AlbumImporter extends StatefulWidget {
   static const routeName = "/album-importer";
 
+  static Route buildRoute(AlbumImporterArguments args) => MaterialPageRoute(
+        builder: (context) => AlbumImporter.fromArgs(args),
+      );
+
   AlbumImporter({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  AlbumImporter.fromArgs(AlbumImporterArguments args, {Key key})
+  AlbumImporter.fromArgs(AlbumImporterArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -98,7 +102,7 @@ class _AlbumImporterState extends State<AlbumImporter> {
             child: Column(
               children: [
                 Text(
-                  AppLocalizations.of(context).albumImporterHeaderText,
+                  AppLocalizations.of(context)!.albumImporterHeaderText,
                   style: Theme.of(context).textTheme.headline5,
                   textAlign: TextAlign.center,
                 ),
@@ -106,7 +110,7 @@ class _AlbumImporterState extends State<AlbumImporter> {
                 Align(
                   alignment: AlignmentDirectional.topStart,
                   child: Text(
-                    AppLocalizations.of(context).albumImporterSubHeaderText,
+                    AppLocalizations.of(context)!.albumImporterSubHeaderText,
                   ),
                 ),
               ],
@@ -141,7 +145,7 @@ class _AlbumImporterState extends State<AlbumImporter> {
                 ),
                 ElevatedButton(
                   onPressed: () => _onImportPressed(context),
-                  child: Text(AppLocalizations.of(context).importButtonLabel),
+                  child: Text(AppLocalizations.of(context)!.importButtonLabel),
                 ),
               ],
             ),
@@ -214,7 +218,7 @@ class _AlbumImporterState extends State<AlbumImporter> {
       barrierDismissible: false,
       context: context,
       builder: (context) => ProcessingDialog(
-          text: AppLocalizations.of(context).albumImporterProgressText),
+          text: AppLocalizations.of(context)!.albumImporterProgressText),
     );
     try {
       await _createAllAlbums(context);
@@ -269,7 +273,7 @@ class _AlbumImporterState extends State<AlbumImporter> {
         .toList();
   }
 
-  ListImportableAlbumBloc _bloc;
+  late ListImportableAlbumBloc _bloc;
 
   var _backingFiles = <File>[];
   final _picks = <File>[];

lib/widget/album_picker_dialog.dart

@@ -18,8 +18,8 @@ import 'package:tuple/tuple.dart';
 
 class AlbumPickerDialog extends StatefulWidget {
   AlbumPickerDialog({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
   @override
@@ -68,7 +68,7 @@ class _AlbumPickerDialogState extends State<AlbumPickerDialog> {
       _reqQuery();
     } else {
       // process the current state
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
         setState(() {
           _onStateChange(context, _bloc.state);
         });
@@ -81,7 +81,7 @@ class _AlbumPickerDialogState extends State<AlbumPickerDialog> {
       SimpleDialogOption(
         onPressed: () => _onNewAlbumPressed(context),
         child: Tooltip(
-          message: AppLocalizations.of(context).createAlbumTooltip,
+          message: AppLocalizations.of(context)!.createAlbumTooltip,
           child: Center(
             child: Icon(
               Icons.add,
@@ -170,7 +170,7 @@ class _AlbumPickerDialogState extends State<AlbumPickerDialog> {
     _bloc.add(ListAlbumBlocQuery(widget.account));
   }
 
-  ListAlbumBloc _bloc;
+  late ListAlbumBloc _bloc;
 
   final _items = <Album>[];
 

lib/widget/album_search_delegate.dart

@@ -18,7 +18,7 @@ class AlbumSearchDelegate extends SearchDelegate {
   AlbumSearchDelegate(BuildContext context, this.account)
       : super(
           searchFieldLabel:
-              AppLocalizations.of(context).albumSearchTextFieldHint,
+              AppLocalizations.of(context)!.albumSearchTextFieldHint,
         ) {
     final fileRepo = FileRepo(FileCachedDataSource());
     final albumRepo = AlbumRepo(AlbumCachedDataSource());
@@ -38,7 +38,7 @@ class AlbumSearchDelegate extends SearchDelegate {
     return [
       IconButton(
         icon: Icon(Icons.clear),
-        tooltip: AppLocalizations.of(context).clearTooltip,
+        tooltip: AppLocalizations.of(context)!.clearTooltip,
         onPressed: () {
           query = "";
         },
@@ -88,7 +88,7 @@ class AlbumSearchDelegate extends SearchDelegate {
             ),
             const SizedBox(height: 8),
             Text(
-              AppLocalizations.of(context).listNoResultsText,
+              AppLocalizations.of(context)!.listNoResultsText,
               style: const TextStyle(fontSize: 24),
             ),
           ],

lib/widget/album_viewer.dart

@@ -42,13 +42,17 @@ class AlbumViewerArguments {
 class AlbumViewer extends StatefulWidget {
   static const routeName = "/album-viewer";
 
+  static Route buildRoute(AlbumViewerArguments args) => MaterialPageRoute(
+        builder: (context) => AlbumViewer.fromArgs(args),
+      );
+
   AlbumViewer({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.album,
+    required this.album,
   }) : super(key: key);
 
-  AlbumViewer.fromArgs(AlbumViewerArguments args, {Key key})
+  AlbumViewer.fromArgs(AlbumViewerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -96,7 +100,7 @@ class _AlbumViewerState extends State<AlbumViewer>
   @override
   enterEditMode() {
     super.enterEditMode();
-    _editAlbum = _album.copyWith();
+    _editAlbum = _album!.copyWith();
     setState(() {
       _transformItems();
     });
@@ -104,7 +108,7 @@ class _AlbumViewerState extends State<AlbumViewer>
     if (!SessionStorage().hasShowDragRearrangeNotification) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).albumEditDragRearrangeNotification),
+            AppLocalizations.of(context)!.albumEditDragRearrangeNotification),
         duration: k.snackBarDurationNormal,
       ));
       SessionStorage().hasShowDragRearrangeNotification = true;
@@ -112,15 +116,15 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   @override
-  validateEditMode() => _editFormKey?.currentState?.validate() == true;
+  validateEditMode() => _editFormKey.currentState?.validate() == true;
 
   @override
   doneEditMode() {
     try {
       // persist the changes
-      _editFormKey.currentState.save();
+      _editFormKey.currentState!.save();
-      final newAlbum = makeEdited(_editAlbum);
+      final newAlbum = makeEdited(_editAlbum!);
-      if (newAlbum.copyWith(lastUpdated: OrNull(_album.lastUpdated)) !=
+      if (newAlbum.copyWith(lastUpdated: OrNull(_album!.lastUpdated)) !=
           _album) {
         _log.info("[doneEditMode] Album modified: $newAlbum");
         final albumRepo = AlbumRepo(AlbumCachedDataSource());
@@ -217,7 +221,7 @@ class _AlbumViewerState extends State<AlbumViewer>
     } else if (isSelectionMode) {
       return _buildSelectionAppBar(context);
     } else {
-      return buildNormalAppBar(context, widget.account, _album);
+      return buildNormalAppBar(context, widget.account, _album!);
     }
   }
 
@@ -226,14 +230,14 @@ class _AlbumViewerState extends State<AlbumViewer>
       if (platform_k.isAndroid)
         IconButton(
           icon: const Icon(Icons.share),
-          tooltip: AppLocalizations.of(context).shareSelectedTooltip,
+          tooltip: AppLocalizations.of(context)!.shareSelectedTooltip,
           onPressed: () {
             _onSelectionAppBarSharePressed(context);
           },
         ),
       IconButton(
         icon: const Icon(Icons.remove),
-        tooltip: AppLocalizations.of(context).removeSelectedFromAlbumTooltip,
+        tooltip: AppLocalizations.of(context)!.removeSelectedFromAlbumTooltip,
         onPressed: () {
           _onSelectionAppBarRemovePressed();
         },
@@ -245,12 +249,12 @@ class _AlbumViewerState extends State<AlbumViewer>
     return buildEditAppBar(context, widget.account, widget.album, actions: [
       IconButton(
         icon: Icon(Icons.text_fields),
-        tooltip: AppLocalizations.of(context).albumAddTextTooltip,
+        tooltip: AppLocalizations.of(context)!.albumAddTextTooltip,
         onPressed: _onEditAppBarAddTextPressed,
       ),
       IconButton(
         icon: Icon(Icons.sort_by_alpha),
-        tooltip: AppLocalizations.of(context).sortTooltip,
+        tooltip: AppLocalizations.of(context)!.sortTooltip,
         onPressed: _onEditAppBarSortPressed,
       ),
     ]);
@@ -279,7 +283,7 @@ class _AlbumViewerState extends State<AlbumViewer>
     if (selected.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content:
-            Text(AppLocalizations.of(context).shareSelectedEmptyNotification),
+            Text(AppLocalizations.of(context)!.shareSelectedEmptyNotification),
         duration: k.snackBarDurationNormal,
       ));
       return;
@@ -301,14 +305,14 @@ class _AlbumViewerState extends State<AlbumViewer>
         .toList();
 
     final albumRepo = AlbumRepo(AlbumCachedDataSource());
-    final newAlbum = _album.copyWith(
+    final newAlbum = _album!.copyWith(
       provider: AlbumStaticProvider(
         items: newItems,
       ),
     );
     UpdateAlbum(albumRepo)(widget.account, newAlbum).then((_) {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .removeSelectedFromAlbumSuccessNotification(
                 selectedIndexes.length)),
         duration: k.snackBarDurationNormal,
@@ -323,7 +327,7 @@ class _AlbumViewerState extends State<AlbumViewer>
           stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            "${AppLocalizations.of(context).removeSelectedFromAlbumFailureNotification}: "
+            "${AppLocalizations.of(context)!.removeSelectedFromAlbumFailureNotification}: "
             "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -334,14 +338,14 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   void _onEditAppBarSortPressed() {
-    final sortProvider = _editAlbum.sortProvider;
+    final sortProvider = _editAlbum!.sortProvider;
     showDialog(
       context: context,
       builder: (context) => FancyOptionPicker(
-        title: AppLocalizations.of(context).sortOptionDialogTitle,
+        title: AppLocalizations.of(context)!.sortOptionDialogTitle,
         items: [
           FancyOptionPickerItem(
-            label: AppLocalizations.of(context).sortOptionTimeAscendingLabel,
+            label: AppLocalizations.of(context)!.sortOptionTimeAscendingLabel,
             isSelected: sortProvider is AlbumTimeSortProvider &&
                 sortProvider.isAscending,
             onSelect: () {
@@ -350,7 +354,7 @@ class _AlbumViewerState extends State<AlbumViewer>
             },
           ),
           FancyOptionPickerItem(
-            label: AppLocalizations.of(context).sortOptionTimeDescendingLabel,
+            label: AppLocalizations.of(context)!.sortOptionTimeDescendingLabel,
             isSelected: sortProvider is AlbumTimeSortProvider &&
                 !sortProvider.isAscending,
             onSelect: () {
@@ -364,7 +368,7 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   void _onSortOldestPressed() {
-    _editAlbum = _editAlbum.copyWith(
+    _editAlbum = _editAlbum!.copyWith(
       sortProvider: AlbumTimeSortProvider(isAscending: true),
     );
     setState(() {
@@ -373,7 +377,7 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   void _onSortNewestPressed() {
-    _editAlbum = _editAlbum.copyWith(
+    _editAlbum = _editAlbum!.copyWith(
       sortProvider: AlbumTimeSortProvider(isAscending: false),
     );
     setState(() {
@@ -431,7 +435,7 @@ class _AlbumViewerState extends State<AlbumViewer>
     final newIndex =
         toIndex + (isBefore ? 0 : 1) + (fromIndex < toIndex ? -1 : 0);
     _sortedItems.insert(newIndex, item);
-    _editAlbum = _editAlbum.copyWith(
+    _editAlbum = _editAlbum!.copyWith(
       sortProvider: AlbumNullSortProvider(),
       // save the current order
       provider: AlbumStaticProvider(
@@ -444,14 +448,14 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   void _onEditAppBarAddTextPressed() {
-    showDialog(
+    showDialog<String>(
       context: context,
       builder: (context) => SimpleInputDialog(),
     ).then((value) {
       if (value == null) {
         return;
       }
-      _editAlbum = _editAlbum.copyWith(
+      _editAlbum = _editAlbum!.copyWith(
         provider: AlbumStaticProvider(
           items: [
             AlbumLabelItem(text: value),
@@ -466,7 +470,7 @@ class _AlbumViewerState extends State<AlbumViewer>
   }
 
   void _onLabelItemEditPressed(AlbumLabelItem item, int index) {
-    showDialog(
+    showDialog<String>(
       context: context,
       builder: (context) => SimpleInputDialog(
         initialText: item.text,
@@ -476,7 +480,7 @@ class _AlbumViewerState extends State<AlbumViewer>
         return;
       }
       _sortedItems[index] = AlbumLabelItem(text: value);
-      _editAlbum = _editAlbum.copyWith(
+      _editAlbum = _editAlbum!.copyWith(
         provider: AlbumStaticProvider(
           items: _sortedItems,
         ),
@@ -490,9 +494,10 @@ class _AlbumViewerState extends State<AlbumViewer>
   void _transformItems() {
     if (_editAlbum != null) {
       // edit mode
-      _sortedItems = _editAlbum.sortProvider.sort(_getAlbumItemsOf(_editAlbum));
+      _sortedItems =
+          _editAlbum!.sortProvider.sort(_getAlbumItemsOf(_editAlbum!));
     } else {
-      _sortedItems = _album.sortProvider.sort(_getAlbumItemsOf(_album));
+      _sortedItems = _album!.sortProvider.sort(_getAlbumItemsOf(_album!));
     }
     _backingFiles = _sortedItems
         .whereType<AlbumFileItem>()
@@ -644,29 +649,29 @@ class _AlbumViewerState extends State<AlbumViewer>
   static List<AlbumItem> _getAlbumItemsOf(Album a) =>
       AlbumStaticProvider.of(a).items;
 
-  Album _album;
+  Album? _album;
   var _sortedItems = <AlbumItem>[];
   var _backingFiles = <File>[];
 
   final _scrollController = ScrollController();
-  double _itemListMaxExtent;
+  double? _itemListMaxExtent;
   bool _isDragging = false;
   // == null if not drag scrolling
-  bool _isDragScrollingDown;
+  bool? _isDragScrollingDown;
   final _editFormKey = GlobalKey<FormState>();
-  Album _editAlbum;
+  Album? _editAlbum;
 
   static final _log = Logger("widget.album_viewer._AlbumViewerState");
 }
 
 abstract class _ListItem implements SelectableItem, DraggableItem {
   _ListItem({
-    @required this.index,
+    required this.index,
-    VoidCallback onTap,
+    VoidCallback? onTap,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   })  : _onTap = onTap,
         _onDropBefore = onDropBefore,
         _onDropAfter = onDropAfter,
@@ -709,22 +714,22 @@ abstract class _ListItem implements SelectableItem, DraggableItem {
 
   final int index;
 
-  final VoidCallback _onTap;
+  final VoidCallback? _onTap;
-  final DragTargetAccept<DraggableItem> _onDropBefore;
+  final DragTargetAccept<DraggableItem>? _onDropBefore;
-  final DragTargetAccept<DraggableItem> _onDropAfter;
+  final DragTargetAccept<DraggableItem>? _onDropAfter;
-  final VoidCallback _onDragStarted;
+  final VoidCallback? _onDragStarted;
-  final VoidCallback _onDragEndedAny;
+  final VoidCallback? _onDragEndedAny;
 }
 
 abstract class _FileListItem extends _ListItem {
   _FileListItem({
-    @required int index,
+    required int index,
-    @required this.file,
+    required this.file,
-    VoidCallback onTap,
+    VoidCallback? onTap,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   }) : super(
           index: index,
           onTap: onTap,
@@ -739,15 +744,15 @@ abstract class _FileListItem extends _ListItem {
 
 class _ImageListItem extends _FileListItem {
   _ImageListItem({
-    @required int index,
+    required int index,
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   }) : super(
           index: index,
           file: file,
@@ -773,15 +778,15 @@ class _ImageListItem extends _FileListItem {
 
 class _VideoListItem extends _FileListItem {
   _VideoListItem({
-    @required int index,
+    required int index,
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   }) : super(
           index: index,
           file: file,
@@ -806,12 +811,12 @@ class _VideoListItem extends _FileListItem {
 
 class _LabelListItem extends _ListItem {
   _LabelListItem({
-    @required int index,
+    required int index,
-    @required this.text,
+    required this.text,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   }) : super(
           index: index,
           onDropBefore: onDropBefore,
@@ -842,13 +847,13 @@ class _LabelListItem extends _ListItem {
 
 class _EditLabelListItem extends _LabelListItem {
   _EditLabelListItem({
-    @required int index,
+    required int index,
-    @required String text,
+    required String text,
-    @required this.onEditPressed,
+    required this.onEditPressed,
-    DragTargetAccept<DraggableItem> onDropBefore,
+    DragTargetAccept<DraggableItem>? onDropBefore,
-    DragTargetAccept<DraggableItem> onDropAfter,
+    DragTargetAccept<DraggableItem>? onDropAfter,
-    VoidCallback onDragStarted,
+    VoidCallback? onDragStarted,
-    VoidCallback onDragEndedAny,
+    VoidCallback? onDragEndedAny,
   }) : super(
           index: index,
           text: text,
@@ -873,7 +878,7 @@ class _EditLabelListItem extends _LabelListItem {
           end: 0,
           child: IconButton(
             icon: Icon(Icons.edit),
-            tooltip: AppLocalizations.of(context).editTooltip,
+            tooltip: AppLocalizations.of(context)!.editTooltip,
             onPressed: onEditPressed,
           ),
         ),
@@ -886,5 +891,5 @@ class _EditLabelListItem extends _LabelListItem {
     return super.buildWidget(context);
   }
 
-  final VoidCallback onEditPressed;
+  final VoidCallback? onEditPressed;
 }

lib/widget/album_viewer_mixin.dart

@@ -18,20 +18,17 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
   @override
   initState() {
     super.initState();
-    _thumbZoomLevel = Pref.inst().getAlbumViewerZoomLevel(0);
+    _thumbZoomLevel = Pref.inst().getAlbumViewerZoomLevelOr(0);
   }
 
   @protected
-  File initCover(Account account, List<File> backingFiles) {
+  void initCover(Account account, List<File> backingFiles) {
     try {
       final coverFile =
-          backingFiles.firstWhere((element) => element.hasPreview);
+          backingFiles.firstWhere((element) => element.hasPreview ?? false);
       _coverPreviewUrl = api_util.getFilePreviewUrl(account, coverFile,
           width: 1024, height: 600);
-      return coverFile;
+    } catch (_) {}
-    } catch (_) {
-      return null;
-    }
   }
 
   @protected
@@ -39,9 +36,9 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
     BuildContext context,
     Account account,
     Album album, {
-    List<Widget> actions,
+    List<Widget>? actions,
-    List<PopupMenuEntry<int>> Function(BuildContext) menuItemBuilder,
+    List<PopupMenuEntry<int>> Function(BuildContext)? menuItemBuilder,
-    void Function(int) onSelectedMenuItem,
+    void Function(int)? onSelectedMenuItem,
   }) {
     return SliverAppBar(
       floating: true,
@@ -58,7 +55,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
       actions: [
         PopupMenuButton(
           icon: const Icon(Icons.photo_size_select_large),
-          tooltip: AppLocalizations.of(context).zoomTooltip,
+          tooltip: AppLocalizations.of(context)!.zoomTooltip,
           itemBuilder: (context) => [
             PopupMenuZoom(
               initialValue: _thumbZoomLevel,
@@ -74,12 +71,12 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
           ],
         ),
         ...(actions ?? []),
-        PopupMenuButton(
+        PopupMenuButton<int>(
           tooltip: MaterialLocalizations.of(context).moreButtonTooltip,
           itemBuilder: (context) => [
             PopupMenuItem(
               value: -1,
-              child: Text(AppLocalizations.of(context).editAlbumMenuLabel),
+              child: Text(AppLocalizations.of(context)!.editAlbumMenuLabel),
             ),
             ...(menuItemBuilder?.call(context) ?? []),
           ],
@@ -120,7 +117,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
             });
           },
         ),
-        title: Text(AppLocalizations.of(context)
+        title: Text(AppLocalizations.of(context)!
             .selectionAppBarTitle(selectedListItems.length)),
         actions: actions,
       ),
@@ -132,7 +129,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
     BuildContext context,
     Account account,
     Album album, {
-    List<Widget> actions,
+    List<Widget>? actions,
   }) {
     return SliverAppBar(
       floating: true,
@@ -141,16 +138,17 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
         background: _getAppBarCover(context, account),
         title: TextFormField(
           decoration: InputDecoration(
-            hintText: AppLocalizations.of(context).nameInputHint,
+            hintText: AppLocalizations.of(context)!.nameInputHint,
           ),
           validator: (value) {
-            if (value.isEmpty) {
+            if (value?.isNotEmpty == true) {
-              return AppLocalizations.of(context).albumNameInputInvalidEmpty;
+              return null;
+            } else {
+              return AppLocalizations.of(context)!.albumNameInputInvalidEmpty;
             }
-            return null;
           },
           onSaved: (value) {
-            _editFormValue.name = value;
+            _editFormValue.name = value!;
           },
           onChanged: (value) {
             // need to save the value otherwise it'll return to the initial
@@ -166,7 +164,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
       leading: IconButton(
         icon: const Icon(Icons.check),
         color: Theme.of(context).colorScheme.primary,
-        tooltip: AppLocalizations.of(context).doneButtonTooltip,
+        tooltip: AppLocalizations.of(context)!.doneButtonTooltip,
         onPressed: () {
           if (validateEditMode()) {
             setState(() {
@@ -226,7 +224,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
     });
   }
 
-  Widget _getAppBarCover(BuildContext context, Account account) {
+  Widget? _getAppBarCover(BuildContext context, Account account) {
     try {
       if (_coverPreviewUrl != null) {
         return Opacity(
@@ -236,7 +234,7 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
             clipBehavior: Clip.hardEdge,
             fit: BoxFit.cover,
             child: CachedNetworkImage(
-              imageUrl: _coverPreviewUrl,
+              imageUrl: _coverPreviewUrl!,
               httpHeaders: {
                 "Authorization": Api.getAuthorizationHeaderValue(account),
               },
@@ -254,11 +252,11 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
     return null;
   }
 
-  String _coverPreviewUrl;
+  String? _coverPreviewUrl;
   var _thumbZoomLevel = 0;
 
   var _isEditMode = false;
-  String _editNameValue;
+  String? _editNameValue;
   var _editFormValue = _EditFormValue();
 
   static final _log = Logger("widget.album_viewer_mixin.AlbumViewerMixin");
@@ -266,5 +264,5 @@ mixin AlbumViewerMixin<T extends StatefulWidget>
 }
 
 class _EditFormValue {
-  String name;
+  late String name;
 }

lib/widget/animated_visibility.dart

@@ -5,14 +5,14 @@ import 'package:flutter/widgets.dart';
 /// The point is to disable non-visible buttons
 class AnimatedVisibility extends StatefulWidget {
   const AnimatedVisibility({
-    Key key,
+    Key? key,
-    this.child,
+    required this.child,
-    @required this.opacity,
+    required this.opacity,
     this.curve = Curves.linear,
-    @required this.duration,
+    required this.duration,
     this.onEnd,
     this.alwaysIncludeSemantics = false,
-  })  : assert(opacity != null && opacity >= 0.0 && opacity <= 1.0),
+  })  : assert(opacity >= 0.0 && opacity <= 1.0),
         super(key: key);
 
   @override
@@ -22,7 +22,7 @@ class AnimatedVisibility extends StatefulWidget {
   final double opacity;
   final Curve curve;
   final Duration duration;
-  final VoidCallback onEnd;
+  final VoidCallback? onEnd;
   final bool alwaysIncludeSemantics;
 }
 

lib/widget/archive_viewer.dart

@@ -32,12 +32,16 @@ class ArchiveViewerArguments {
 class ArchiveViewer extends StatefulWidget {
   static const routeName = "/archive-viewer";
 
+  static Route buildRoute(ArchiveViewerArguments args) => MaterialPageRoute(
+        builder: (context) => ArchiveViewer.fromArgs(args),
+      );
+
   ArchiveViewer({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  ArchiveViewer.fromArgs(ArchiveViewerArguments args, {Key key})
+  ArchiveViewer.fromArgs(ArchiveViewerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -55,7 +59,7 @@ class _ArchiveViewerState extends State<ArchiveViewer>
   initState() {
     super.initState();
     _initBloc();
-    _thumbZoomLevel = Pref.inst().getAlbumViewerZoomLevel(0);
+    _thumbZoomLevel = Pref.inst().getAlbumViewerZoomLevelOr(0);
   }
 
   @override
@@ -81,7 +85,7 @@ class _ArchiveViewerState extends State<ArchiveViewer>
       _reqQuery();
     } else {
       // process the current state
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
         setState(() {
           _onStateChange(context, _bloc.state);
         });
@@ -144,12 +148,12 @@ class _ArchiveViewerState extends State<ArchiveViewer>
             });
           },
         ),
-        title: Text(AppLocalizations.of(context)
+        title: Text(AppLocalizations.of(context)!
             .selectionAppBarTitle(selectedListItems.length)),
         actions: [
           IconButton(
             icon: const Icon(Icons.unarchive),
-            tooltip: AppLocalizations.of(context).unarchiveSelectedTooltip,
+            tooltip: AppLocalizations.of(context)!.unarchiveSelectedTooltip,
             onPressed: () {
               _onSelectionAppBarUnarchivePressed();
             },
@@ -161,12 +165,12 @@ class _ArchiveViewerState extends State<ArchiveViewer>
 
   Widget _buildNormalAppBar(BuildContext context) {
     return SliverAppBar(
-      title: Text(AppLocalizations.of(context).albumArchiveLabel),
+      title: Text(AppLocalizations.of(context)!.albumArchiveLabel),
       floating: true,
       actions: [
         PopupMenuButton(
           icon: const Icon(Icons.photo_size_select_large),
-          tooltip: AppLocalizations.of(context).zoomTooltip,
+          tooltip: AppLocalizations.of(context)!.zoomTooltip,
           itemBuilder: (context) => [
             PopupMenuZoom(
               initialValue: _thumbZoomLevel,
@@ -208,7 +212,7 @@ class _ArchiveViewerState extends State<ArchiveViewer>
 
   Future<void> _onSelectionAppBarUnarchivePressed() async {
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context)
+      content: Text(AppLocalizations.of(context)!
           .unarchiveSelectedProcessingNotification(selectedListItems.length)),
       duration: k.snackBarDurationShort,
     ));
@@ -237,12 +241,12 @@ class _ArchiveViewerState extends State<ArchiveViewer>
     if (failures.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).unarchiveSelectedSuccessNotification),
+            AppLocalizations.of(context)!.unarchiveSelectedSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .unarchiveSelectedFailureNotification(failures.length)),
         duration: k.snackBarDurationNormal,
       ));
@@ -308,7 +312,7 @@ class _ArchiveViewerState extends State<ArchiveViewer>
     }
   }
 
-  ScanDirBloc _bloc;
+  late ScanDirBloc _bloc;
 
   var _backingFiles = <File>[];
 
@@ -319,7 +323,7 @@ class _ArchiveViewerState extends State<ArchiveViewer>
 
 abstract class _ListItem implements SelectableItem {
   _ListItem({
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : _onTap = onTap;
 
   @override
@@ -331,13 +335,13 @@ abstract class _ListItem implements SelectableItem {
   @override
   get staggeredTile => const StaggeredTile.count(1, 1);
 
-  final VoidCallback _onTap;
+  final VoidCallback? _onTap;
 }
 
 abstract class _FileListItem extends _ListItem {
   _FileListItem({
-    @required this.file,
+    required this.file,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(onTap: onTap);
 
   @override
@@ -353,10 +357,10 @@ abstract class _FileListItem extends _ListItem {
 
 class _ImageListItem extends _FileListItem {
   _ImageListItem({
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(file: file, onTap: onTap);
 
   @override
@@ -374,10 +378,10 @@ class _ImageListItem extends _FileListItem {
 
 class _VideoListItem extends _FileListItem {
   _VideoListItem({
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(file: file, onTap: onTap);
 
   @override

lib/widget/builder/album_grid_item_builder.dart

@@ -13,8 +13,8 @@ import 'package:nc_photos/widget/album_grid_item.dart';
 /// Build a standard [AlbumGridItem] for an [Album]
 class AlbumGridItemBuilder {
   AlbumGridItemBuilder({
-    @required this.account,
+    required this.account,
-    @required this.album,
+    required this.album,
     this.isSelected = false,
     this.onTap,
     this.onLongPress,
@@ -22,9 +22,9 @@ class AlbumGridItemBuilder {
 
   AlbumGridItem build(BuildContext context) {
     var subtitle = "";
-    String subtitle2;
+    String? subtitle2;
     if (album.provider is AlbumStaticProvider) {
-      subtitle = AppLocalizations.of(context)
+      subtitle = AppLocalizations.of(context)!
           .albumSize(AlbumStaticProvider.of(album).items.length);
     } else if (album.provider is AlbumDirProvider) {
       final provider = album.provider as AlbumDirProvider;
@@ -49,7 +49,7 @@ class AlbumGridItemBuilder {
     Widget cover;
     try {
       final coverFile = album.coverProvider.getCover(album);
-      final previewUrl = api_util.getFilePreviewUrl(account, coverFile,
+      final previewUrl = api_util.getFilePreviewUrl(account, coverFile!,
           width: 512, height: 512);
       cover = FittedBox(
         clipBehavior: Clip.hardEdge,
@@ -89,6 +89,6 @@ class AlbumGridItemBuilder {
   final Account account;
   final Album album;
   final bool isSelected;
-  final VoidCallback onTap;
+  final VoidCallback? onTap;
-  final VoidCallback onLongPress;
+  final VoidCallback? onLongPress;
 }

lib/widget/cached_network_image_mod.dart

@@ -21,8 +21,8 @@ class CachedNetworkImage extends StatelessWidget {
   /// to clear the image from the [ImageCache].
   static Future evictFromCache(
     String url, {
-    String cacheKey,
+    String? cacheKey,
-    BaseCacheManager cacheManager,
+    BaseCacheManager? cacheManager,
     double scale = 1.0,
   }) async {
     cacheManager = cacheManager ?? DefaultCacheManager();
@@ -33,31 +33,31 @@ class CachedNetworkImage extends StatelessWidget {
   final CachedNetworkImageProvider _image;
 
   /// Option to use cachemanager with other settings
-  final BaseCacheManager cacheManager;
+  final BaseCacheManager? cacheManager;
 
   /// The target image that is displayed.
   final String imageUrl;
 
   /// The target image's cache key.
-  final String cacheKey;
+  final String? cacheKey;
 
   /// Optional builder to further customize the display of the image.
-  final ImageWidgetBuilder imageBuilder;
+  final ImageWidgetBuilder? imageBuilder;
 
   /// Widget displayed while the target [imageUrl] is loading.
-  final PlaceholderWidgetBuilder placeholder;
+  final PlaceholderWidgetBuilder? placeholder;
 
   /// Widget displayed while the target [imageUrl] is loading.
-  final ProgressIndicatorBuilder progressIndicatorBuilder;
+  final ProgressIndicatorBuilder? progressIndicatorBuilder;
 
   /// Widget displayed while the target [imageUrl] failed loading.
-  final LoadingErrorWidgetBuilder errorWidget;
+  final LoadingErrorWidgetBuilder? errorWidget;
 
   /// The duration of the fade-in animation for the [placeholder].
-  final Duration placeholderFadeInDuration;
+  final Duration? placeholderFadeInDuration;
 
   /// The duration of the fade-out animation for the [placeholder].
-  final Duration fadeOutDuration;
+  final Duration? fadeOutDuration;
 
   /// The curve of the fade-out animation for the [placeholder].
   final Curve fadeOutCurve;
@@ -74,7 +74,7 @@ class CachedNetworkImage extends StatelessWidget {
   /// aspect ratio. This may result in a sudden change if the size of the
   /// placeholder widget does not match that of the target image. The size is
   /// also affected by the scale factor.
-  final double width;
+  final double? width;
 
   /// If non-null, require the image to have this height.
   ///
@@ -82,13 +82,13 @@ class CachedNetworkImage extends StatelessWidget {
   /// aspect ratio. This may result in a sudden change if the size of the
   /// placeholder widget does not match that of the target image. The size is
   /// also affected by the scale factor.
-  final double height;
+  final double? height;
 
   /// How to inscribe the image into the space allocated during layout.
   ///
   /// The default varies based on the other fields. See the discussion at
   /// [paintImage].
-  final BoxFit fit;
+  final BoxFit? fit;
 
   /// How to align the image within its bounds.
   ///
@@ -112,7 +112,7 @@ class CachedNetworkImage extends StatelessWidget {
   ///    specify an [AlignmentGeometry].
   ///  * [AlignmentDirectional], like [Alignment] for specifying alignments
   ///    relative to text direction.
-  final AlignmentGeometry alignment;
+  final Alignment alignment;
 
   /// How to paint any portions of the layout bounds not covered by the image.
   final ImageRepeat repeat;
@@ -135,14 +135,14 @@ class CachedNetworkImage extends StatelessWidget {
   final bool matchTextDirection;
 
   /// Optional headers for the http request of the image url
-  final Map<String, String> httpHeaders;
+  final Map<String, String>? httpHeaders;
 
   /// When set to true it will animate from the old image to the new image
   /// if the url changes.
   final bool useOldImageOnUrlChange;
 
   /// If non-null, this color is blended with each image pixel using [colorBlendMode].
-  final Color color;
+  final Color? color;
 
   /// Used to combine [color] with this image.
   ///
@@ -152,7 +152,7 @@ class CachedNetworkImage extends StatelessWidget {
   /// See also:
   ///
   ///  * [BlendMode], which includes an illustration of the effect of each blend mode.
-  final BlendMode colorBlendMode;
+  final BlendMode? colorBlendMode;
 
   /// Target the interpolation quality for image scaling.
   ///
@@ -160,24 +160,24 @@ class CachedNetworkImage extends StatelessWidget {
   final FilterQuality filterQuality;
 
   /// Will resize the image in memory to have a certain width using [ResizeImage]
-  final int memCacheWidth;
+  final int? memCacheWidth;
 
   /// Will resize the image in memory to have a certain height using [ResizeImage]
-  final int memCacheHeight;
+  final int? memCacheHeight;
 
   /// Will resize the image and store the resized image in the disk cache.
-  final int maxWidthDiskCache;
+  final int? maxWidthDiskCache;
 
   /// Will resize the image and store the resized image in the disk cache.
-  final int maxHeightDiskCache;
+  final int? maxHeightDiskCache;
 
   /// CachedNetworkImage shows a network image using a caching mechanism. It also
   /// provides support for a placeholder, showing an error and fading into the
   /// loaded image. Next to that it supports most features of a default Image
   /// widget.
   CachedNetworkImage({
-    Key key,
+    Key? key,
-    @required this.imageUrl,
+    required this.imageUrl,
     this.httpHeaders,
     this.imageBuilder,
     this.placeholder,
@@ -204,17 +204,8 @@ class CachedNetworkImage extends StatelessWidget {
     this.cacheKey,
     this.maxWidthDiskCache,
     this.maxHeightDiskCache,
-    ImageRenderMethodForWeb imageRenderMethodForWeb,
+    ImageRenderMethodForWeb? imageRenderMethodForWeb,
-  })  : assert(imageUrl != null),
+  })  : _image = CachedNetworkImageProvider(
-        assert(fadeOutDuration != null),
-        assert(fadeOutCurve != null),
-        assert(fadeInDuration != null),
-        assert(fadeInCurve != null),
-        assert(alignment != null),
-        assert(filterQuality != null),
-        assert(repeat != null),
-        assert(matchTextDirection != null),
-        _image = CachedNetworkImageProvider(
           imageUrl,
           headers: httpHeaders,
           cacheManager: cacheManager,
@@ -267,32 +258,32 @@ class CachedNetworkImage extends StatelessWidget {
   }
 
   Widget _octoImageBuilder(BuildContext context, Widget child) {
-    return imageBuilder(context, child, _image);
+    return imageBuilder!(context, child, _image);
   }
 
   Widget _octoPlaceholderBuilder(BuildContext context) {
-    return placeholder(context, imageUrl);
+    return placeholder!(context, imageUrl);
   }
 
   Widget _octoProgressIndicatorBuilder(
     BuildContext context,
-    ImageChunkEvent progress,
+    ImageChunkEvent? progress,
   ) {
-    int totalSize;
+    int? totalSize;
     var downloaded = 0;
     if (progress != null) {
       totalSize = progress.expectedTotalBytes;
       downloaded = progress.cumulativeBytesLoaded;
     }
-    return progressIndicatorBuilder(
+    return progressIndicatorBuilder!(
         context, imageUrl, DownloadProgress(imageUrl, totalSize, downloaded));
   }
 
   Widget _octoErrorBuilder(
     BuildContext context,
     Object error,
-    StackTrace stackTrace,
+    StackTrace? stackTrace,
   ) {
-    return errorWidget(context, imageUrl, error);
+    return errorWidget!(context, imageUrl, error);
   }
 }

lib/widget/connect.dart

@@ -25,12 +25,16 @@ class ConnectArguments {
 class Connect extends StatefulWidget {
   static const routeName = "/connect";
 
+  static Route buildRoute(ConnectArguments args) => MaterialPageRoute<Account>(
+        builder: (context) => Connect.fromArgs(args),
+      );
+
   Connect({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  Connect.fromArgs(ConnectArguments args, {Key key})
+  Connect.fromArgs(ConnectArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -82,7 +86,7 @@ class _ConnectState extends State<Connect> {
               color: Theme.of(context).colorScheme.primary,
             ),
             Text(
-              AppLocalizations.of(context)
+              AppLocalizations.of(context)!
                   .connectingToServer(widget.account.url),
               textAlign: TextAlign.center,
               style: Theme.of(context).textTheme.headline6,
@@ -106,7 +110,7 @@ class _ConnectState extends State<Connect> {
       } else if (state.exception is ApiException &&
           (state.exception as ApiException).response.statusCode == 401) {
         SnackBarManager().showSnackBar(SnackBar(
-          content: Text(AppLocalizations.of(context).errorWrongPassword),
+          content: Text(AppLocalizations.of(context)!.errorWrongPassword),
           duration: k.snackBarDurationNormal,
         ));
         Navigator.of(context).pop(null);
@@ -124,9 +128,9 @@ class _ConnectState extends State<Connect> {
     showDialog(
       context: context,
       builder: (context) => AlertDialog(
-        title: Text(AppLocalizations.of(context).serverCertErrorDialogTitle),
+        title: Text(AppLocalizations.of(context)!.serverCertErrorDialogTitle),
         content:
-            Text(AppLocalizations.of(context).serverCertErrorDialogContent),
+            Text(AppLocalizations.of(context)!.serverCertErrorDialogContent),
         actions: <Widget>[
           TextButton(
             onPressed: () {
@@ -138,7 +142,7 @@ class _ConnectState extends State<Connect> {
             onPressed: () {
               Navigator.of(context).pop(true);
             },
-            child: Text(AppLocalizations.of(context).advancedButtonLabel),
+            child: Text(AppLocalizations.of(context)!.advancedButtonLabel),
           ),
         ],
       ),
@@ -150,10 +154,11 @@ class _ConnectState extends State<Connect> {
       showDialog(
         context: context,
         builder: (context) => AlertDialog(
-          title: Text(AppLocalizations.of(context).whitelistCertDialogTitle),
+          title: Text(AppLocalizations.of(context)!.whitelistCertDialogTitle),
-          content: Text(AppLocalizations.of(context).whitelistCertDialogContent(
+          content: Text(AppLocalizations.of(context)!
-              SelfSignedCertManager().getLastBadCertHost(),
+              .whitelistCertDialogContent(
-              SelfSignedCertManager().getLastBadCertFingerprint())),
+                  SelfSignedCertManager().getLastBadCertHost(),
+                  SelfSignedCertManager().getLastBadCertFingerprint())),
           actions: <Widget>[
             TextButton(
               onPressed: () {
@@ -166,7 +171,7 @@ class _ConnectState extends State<Connect> {
                 Navigator.of(context).pop(true);
               },
               child:
-                  Text(AppLocalizations.of(context).whitelistCertButtonLabel),
+                  Text(AppLocalizations.of(context)!.whitelistCertButtonLabel),
             ),
           ],
         ),

lib/widget/dir_picker_mixin.dart

@@ -100,7 +100,7 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
                 dense: true,
                 leading: const SizedBox(width: 24),
                 title: Text(
-                    AppLocalizations.of(context).rootPickerNavigateUpItemText),
+                    AppLocalizations.of(context)!.rootPickerNavigateUpItemText),
                 onTap: () {
                   try {
                     _navigateInto(File(path: path.dirname(_currentPath)));
@@ -128,7 +128,7 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
     final canPick = canPickDir(item.file);
     final pickState = _isItemPicked(item);
 
-    IconData iconData;
+    IconData? iconData;
     if (canPick) {
       switch (pickState) {
         case _PickState.picked:
@@ -170,9 +170,10 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
               onPressed: null,
             ),
       title: Text(path.basename(item.file.path)),
-      trailing:
+      trailing: item.children?.isNotEmpty == true
-          item.children.isNotEmpty ? const Icon(Icons.arrow_forward_ios) : null,
+          ? const Icon(Icons.arrow_forward_ios)
-      onTap: item.children.isNotEmpty
+          : null,
+      onTap: item.children?.isNotEmpty == true
           ? () {
               try {
                 _navigateInto(item.file);
@@ -238,12 +239,12 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
       // this dir is explicitly picked, nothing more to do
       return [item.file];
     }
-    if (item.children == null || item.children.isEmpty) {
+    if (item.children == null || item.children!.isEmpty) {
       return [];
     }
 
     final products = <File>[];
-    for (final i in item.children) {
+    for (final i in item.children!) {
       products.addAll(_optimizePicks(i));
     }
     // // see if all children are being picked
@@ -282,7 +283,7 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
           _picks.removeWhere((element) => identical(element, parent));
         } catch (_) {
           SnackBarManager().showSnackBar(SnackBar(
-              content: Text(AppLocalizations.of(context)
+              content: Text(AppLocalizations.of(context)!
                   .rootPickerUnpickFailureNotification)));
         }
       }
@@ -296,12 +297,13 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
   /// Either [path] or [item] must be set, If both are set, [item] takes
   /// priority
   List<LsDirBlocItem> _pickedAllExclude({
-    String path,
+    String? path,
-    LsDirBlocItem item,
+    LsDirBlocItem? item,
-    @required LsDirBlocItem exclude,
+    required LsDirBlocItem exclude,
   }) {
+    assert(path != null || item != null);
     if (item == null) {
-      final item = _findChildItemByPath(_root, path);
+      final item = _findChildItemByPath(_root, path!);
       return _pickedAllExclude(item: item, exclude: exclude);
     }
 
@@ -311,7 +313,7 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
     _log.fine(
         "[_pickedAllExclude] Unpicking '${item.file.path}' and picking children");
     final products = <LsDirBlocItem>[];
-    for (final i in item.children) {
+    for (final i in item.children ?? []) {
       if (exclude.file.path.startsWith(i.file.path)) {
         // [i] is a parent of exclude
         products.addAll(_pickedAllExclude(item: i, exclude: exclude));
@@ -327,7 +329,7 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
     if (path == parent.file.path) {
       return parent;
     }
-    for (final c in parent.children) {
+    for (final c in parent.children ?? []) {
       if (path == c.file.path || path.startsWith("${c.file.path}/")) {
         return _findChildItemByPath(c, path);
       }
@@ -364,11 +366,11 @@ mixin DirPickerMixin<T extends StatefulWidget> on State<T> {
     _bloc.add(LsDirBlocQuery(getAccount(), file, depth: 2));
   }
 
-  LsDirBloc _bloc;
+  late LsDirBloc _bloc;
-  LsDirBlocItem _root;
+  late LsDirBlocItem _root;
 
   /// Track where the user is navigating in [_backingFiles]
-  String _currentPath;
+  late String _currentPath;
   var _picks = <File>[];
 
   static final _log = Logger("widget.dir_picker_mixin.DirPickerMixin");

lib/widget/draggable.dart

@@ -2,11 +2,11 @@ import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:logging/logging.dart';
 
-class Draggable<T> extends StatelessWidget {
+class Draggable<T extends Object> extends StatelessWidget {
   Draggable({
-    Key key,
+    Key? key,
-    @required this.data,
+    required this.data,
-    @required this.child,
+    required this.child,
     this.feedback,
     this.onDropBefore,
     this.onDropAfter,
@@ -79,7 +79,7 @@ class Draggable<T> extends StatelessWidget {
                       },
                       onAccept: (item) {
                         _log.fine("[build] Dropping $item before $data");
-                        onDropBefore(item);
+                        onDropBefore!(item);
                       },
                     ),
                   ),
@@ -92,7 +92,7 @@ class Draggable<T> extends StatelessWidget {
                       },
                       onAccept: (item) {
                         _log.fine("[build] Dropping $item after $data");
-                        onDropAfter(item);
+                        onDropAfter!(item);
                       },
                     ),
                   ),
@@ -105,26 +105,26 @@ class Draggable<T> extends StatelessWidget {
 
   final T data;
   final Widget child;
-  final Widget feedback;
+  final Widget? feedback;
 
   /// Called when some item dropped before this item
-  final DragTargetAccept<T> onDropBefore;
+  final DragTargetAccept<T>? onDropBefore;
 
   /// Called when some item dropped after this item
-  final DragTargetAccept<T> onDropAfter;
+  final DragTargetAccept<T>? onDropAfter;
 
-  final VoidCallback onDragStarted;
+  final VoidCallback? onDragStarted;
 
   /// Called when either one of onDragEnd, onDragCompleted or
   /// onDraggableCanceled is called.
   ///
   /// The callback might be called multiple times per each drag event
-  final VoidCallback onDragEndedAny;
+  final VoidCallback? onDragEndedAny;
 
   /// Size of the feedback widget that appears under the pointer.
   ///
   /// Right now a translucent version of [child] is being shown
-  final Size feedbackSize;
+  final Size? feedbackSize;
 
   static final _log = Logger("widget.draggable.Draggable");
 }

lib/widget/draggable_item_list_mixin.dart

@@ -9,21 +9,21 @@ abstract class DraggableItem {
   /// The widget to show under the pointer when a drag is under way.
   ///
   /// Return null if you wish to just use the same widget as display
-  Widget buildDragFeedbackWidget(BuildContext context) => null;
+  Widget? buildDragFeedbackWidget(BuildContext context) => null;
 
   bool get isDraggable => false;
-  DragTargetAccept<DraggableItem> get onDropBefore => null;
+  DragTargetAccept<DraggableItem>? get onDropBefore => null;
-  DragTargetAccept<DraggableItem> get onDropAfter => null;
+  DragTargetAccept<DraggableItem>? get onDropAfter => null;
-  VoidCallback get onDragStarted => null;
+  VoidCallback? get onDragStarted => null;
-  VoidCallback get onDragEndedAny => null;
+  VoidCallback? get onDragEndedAny => null;
   StaggeredTile get staggeredTile => const StaggeredTile.count(1, 1);
 }
 
 mixin DraggableItemListMixin<T extends StatefulWidget> on State<T> {
   @protected
   Widget buildDraggableItemList({
-    @required double maxCrossAxisExtent,
+    required double maxCrossAxisExtent,
-    ValueChanged<double> onMaxExtentChanged,
+    ValueChanged<double?>? onMaxExtentChanged,
   }) {
     _maxCrossAxisExtent = maxCrossAxisExtent;
     return MeasurableItemList(
@@ -50,12 +50,10 @@ mixin DraggableItemListMixin<T extends StatefulWidget> on State<T> {
       onDropAfter: item.onDropAfter,
       onDragStarted: item.onDragStarted,
       onDragEndedAny: item.onDragEndedAny,
-      feedbackSize: _maxCrossAxisExtent != null
+      feedbackSize: Size(_maxCrossAxisExtent * .65, _maxCrossAxisExtent * .65),
-          ? Size(_maxCrossAxisExtent * .65, _maxCrossAxisExtent * .65)
-          : null,
     );
   }
 
   var _items = <DraggableItem>[];
-  double _maxCrossAxisExtent;
+  late double _maxCrossAxisExtent;
 }

lib/widget/dynamic_album_viewer.dart

@@ -43,13 +43,18 @@ class DynamicAlbumViewerArguments {
 class DynamicAlbumViewer extends StatefulWidget {
   static const routeName = "/dynamic-album-viewer";
 
+  static Route buildRoute(DynamicAlbumViewerArguments args) =>
+      MaterialPageRoute(
+        builder: (context) => DynamicAlbumViewer.fromArgs(args),
+      );
+
   DynamicAlbumViewer({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.album,
+    required this.album,
   }) : super(key: key);
 
-  DynamicAlbumViewer.fromArgs(DynamicAlbumViewerArguments args, {Key key})
+  DynamicAlbumViewer.fromArgs(DynamicAlbumViewerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -96,19 +101,19 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
   @override
   enterEditMode() {
     super.enterEditMode();
-    _editAlbum = _album.copyWith();
+    _editAlbum = _album!.copyWith();
   }
 
   @override
-  validateEditMode() => _editFormKey?.currentState?.validate() == true;
+  validateEditMode() => _editFormKey.currentState?.validate() == true;
 
   @override
   doneEditMode() {
     try {
       // persist the changes
-      _editFormKey.currentState.save();
+      _editFormKey.currentState!.save();
-      final newAlbum = makeEdited(_editAlbum);
+      final newAlbum = makeEdited(_editAlbum!);
-      if (newAlbum.copyWith(lastUpdated: OrNull(_album.lastUpdated)) !=
+      if (newAlbum.copyWith(lastUpdated: OrNull(_album!.lastUpdated)) !=
           _album) {
         _log.info("[doneEditMode] Album modified: $newAlbum");
         final albumRepo = AlbumRepo(AlbumCachedDataSource());
@@ -142,14 +147,14 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
         setState(() {
           _album = widget.album;
           _transformItems(items);
-          final coverFile = initCover(widget.account, _backingFiles);
+          initCover(widget.account, _backingFiles);
-          _updateAlbumPostPopulate(coverFile, items);
+          _updateAlbumPostPopulate(items);
         });
       }
     });
   }
 
-  void _updateAlbumPostPopulate(File coverFile, List<AlbumItem> items) {
+  void _updateAlbumPostPopulate(List<AlbumItem> items) {
     List<File> timeDescSortedFiles;
     if (widget.album.sortProvider is AlbumTimeSortProvider) {
       if ((widget.album.sortProvider as AlbumTimeSortProvider).isAscending) {
@@ -168,7 +173,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
 
     bool shouldUpdate = false;
     final albumUpdatedCover = UpdateDynamicAlbumCover()
-        .updateWithSortedFiles(_album, timeDescSortedFiles);
+        .updateWithSortedFiles(_album!, timeDescSortedFiles);
     if (!identical(albumUpdatedCover, _album)) {
       _log.info("[_updateAlbumPostPopulate] Update album cover");
       shouldUpdate = true;
@@ -176,7 +181,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     _album = albumUpdatedCover;
 
     final albumUpdatedTime = UpdateDynamicAlbumTime()
-        .updateWithSortedFiles(_album, timeDescSortedFiles);
+        .updateWithSortedFiles(_album!, timeDescSortedFiles);
     if (!identical(albumUpdatedTime, _album)) {
       _log.info(
           "[_updateAlbumPostPopulate] Update album time: ${albumUpdatedTime.provider.latestItemTime}");
@@ -185,7 +190,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     _album = albumUpdatedTime;
 
     if (shouldUpdate) {
-      UpdateAlbum(AlbumRepo(AlbumCachedDataSource()))(widget.account, _album);
+      UpdateAlbum(AlbumRepo(AlbumCachedDataSource()))(widget.account, _album!);
     }
   }
 
@@ -241,11 +246,11 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     return buildNormalAppBar(
       context,
       widget.account,
-      _album,
+      _album!,
       menuItemBuilder: (context) => [
         PopupMenuItem(
           value: _menuValueConvertBasic,
-          child: Text(AppLocalizations.of(context).convertBasicAlbumMenuLabel),
+          child: Text(AppLocalizations.of(context)!.convertBasicAlbumMenuLabel),
         ),
       ],
       onSelectedMenuItem: (option) {
@@ -267,7 +272,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
       if (platform_k.isAndroid)
         IconButton(
           icon: const Icon(Icons.share),
-          tooltip: AppLocalizations.of(context).shareSelectedTooltip,
+          tooltip: AppLocalizations.of(context)!.shareSelectedTooltip,
           onPressed: () {
             _onSelectionAppBarSharePressed(context);
           },
@@ -277,7 +282,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
         itemBuilder: (context) => [
           PopupMenuItem(
             value: _SelectionAppBarOption.delete,
-            child: Text(AppLocalizations.of(context).deleteSelectedTooltip),
+            child: Text(AppLocalizations.of(context)!.deleteSelectedTooltip),
           ),
         ],
         onSelected: (option) {
@@ -293,7 +298,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     return buildEditAppBar(context, widget.account, widget.album, actions: [
       IconButton(
         icon: Icon(Icons.sort_by_alpha),
-        tooltip: AppLocalizations.of(context).sortTooltip,
+        tooltip: AppLocalizations.of(context)!.sortTooltip,
         onPressed: _onEditAppBarSortPressed,
       ),
     ]);
@@ -317,9 +322,9 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     showDialog(
       context: context,
       builder: (context) => AlertDialog(
-        title: Text(AppLocalizations.of(context)
+        title: Text(AppLocalizations.of(context)!
             .convertBasicAlbumConfirmationDialogTitle),
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .convertBasicAlbumConfirmationDialogContent),
         actions: <Widget>[
           TextButton(
@@ -341,17 +346,17 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
         return;
       }
       _log.info(
-          "[_onAppBarConvertBasicPressed] Converting album '${_album.name}' to static");
+          "[_onAppBarConvertBasicPressed] Converting album '${_album!.name}' to static");
       final albumRepo = AlbumRepo(AlbumCachedDataSource());
       UpdateAlbum(albumRepo)(
         widget.account,
-        _album.copyWith(
+        _album!.copyWith(
           provider: AlbumStaticProvider(items: _sortedItems),
           coverProvider: AlbumAutoCoverProvider(),
         ),
       ).then((value) {
         SnackBarManager().showSnackBar(SnackBar(
-          content: Text(AppLocalizations.of(context)
+          content: Text(AppLocalizations.of(context)!
               .convertBasicAlbumSuccessNotification),
           duration: k.snackBarDurationNormal,
         ));
@@ -386,7 +391,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
 
   void _onSelectionAppBarDeletePressed() async {
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context)
+      content: Text(AppLocalizations.of(context)!
           .deleteSelectedProcessingNotification(selectedListItems.length)),
       duration: k.snackBarDurationShort,
     ));
@@ -417,12 +422,12 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
     if (failures.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).deleteSelectedSuccessNotification),
+            AppLocalizations.of(context)!.deleteSelectedSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .deleteSelectedFailureNotification(failures.length)),
         duration: k.snackBarDurationNormal,
       ));
@@ -439,14 +444,14 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
   }
 
   void _onEditAppBarSortPressed() {
-    final sortProvider = _editAlbum.sortProvider;
+    final sortProvider = _editAlbum!.sortProvider;
     showDialog(
       context: context,
       builder: (context) => FancyOptionPicker(
-        title: AppLocalizations.of(context).sortOptionDialogTitle,
+        title: AppLocalizations.of(context)!.sortOptionDialogTitle,
         items: [
           FancyOptionPickerItem(
-            label: AppLocalizations.of(context).sortOptionTimeAscendingLabel,
+            label: AppLocalizations.of(context)!.sortOptionTimeAscendingLabel,
             isSelected: sortProvider is AlbumTimeSortProvider &&
                 sortProvider.isAscending,
             onSelect: () {
@@ -455,7 +460,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
             },
           ),
           FancyOptionPickerItem(
-            label: AppLocalizations.of(context).sortOptionTimeDescendingLabel,
+            label: AppLocalizations.of(context)!.sortOptionTimeDescendingLabel,
             isSelected: sortProvider is AlbumTimeSortProvider &&
                 !sortProvider.isAscending,
             onSelect: () {
@@ -469,7 +474,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
   }
 
   void _onSortOldestPressed() {
-    _editAlbum = _editAlbum.copyWith(
+    _editAlbum = _editAlbum!.copyWith(
       sortProvider: AlbumTimeSortProvider(isAscending: true),
     );
     setState(() {
@@ -478,7 +483,7 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
   }
 
   void _onSortNewestPressed() {
-    _editAlbum = _editAlbum.copyWith(
+    _editAlbum = _editAlbum!.copyWith(
       sortProvider: AlbumTimeSortProvider(isAscending: false),
     );
     setState(() {
@@ -489,9 +494,9 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
   void _transformItems(List<AlbumItem> items) {
     if (_editAlbum != null) {
       // edit mode
-      _sortedItems = _editAlbum.sortProvider.sort(items);
+      _sortedItems = _editAlbum!.sortProvider.sort(items);
     } else {
-      _sortedItems = _album.sortProvider.sort(items);
+      _sortedItems = _album!.sortProvider.sort(items);
     }
     _onSortedItemsUpdated();
   }
@@ -535,12 +540,12 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
         .toList();
   }
 
-  Album _album;
+  Album? _album;
   var _sortedItems = <AlbumItem>[];
   var _backingFiles = <File>[];
 
   final _editFormKey = GlobalKey<FormState>();
-  Album _editAlbum;
+  Album? _editAlbum;
 
   static final _log =
       Logger("widget.dynamic_album_viewer._DynamicAlbumViewerState");
@@ -549,8 +554,8 @@ class _DynamicAlbumViewerState extends State<DynamicAlbumViewer>
 
 abstract class _ListItem implements SelectableItem {
   _ListItem({
-    @required this.index,
+    required this.index,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : _onTap = onTap;
 
   @override
@@ -571,14 +576,14 @@ abstract class _ListItem implements SelectableItem {
 
   final int index;
 
-  final VoidCallback _onTap;
+  final VoidCallback? _onTap;
 }
 
 abstract class _FileListItem extends _ListItem {
   _FileListItem({
-    @required int index,
+    required int index,
-    @required this.file,
+    required this.file,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(
           index: index,
           onTap: onTap,
@@ -589,11 +594,11 @@ abstract class _FileListItem extends _ListItem {
 
 class _ImageListItem extends _FileListItem {
   _ImageListItem({
-    @required int index,
+    required int index,
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(
           index: index,
           file: file,
@@ -615,11 +620,11 @@ class _ImageListItem extends _FileListItem {
 
 class _VideoListItem extends _FileListItem {
   _VideoListItem({
-    @required int index,
+    required int index,
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(
           index: index,
           file: file,

lib/widget/fancy_option_picker.dart

@@ -3,28 +3,28 @@ import 'package:flutter/widgets.dart';
 
 class FancyOptionPickerItem {
   FancyOptionPickerItem({
-    @required this.label,
+    required this.label,
     this.isSelected = false,
     this.onSelect,
   });
 
   String label;
   bool isSelected;
-  VoidCallback onSelect;
+  VoidCallback? onSelect;
 }
 
 /// A fancy looking dialog to pick an option
 class FancyOptionPicker extends StatelessWidget {
   FancyOptionPicker({
-    Key key,
+    Key? key,
     this.title,
-    @required this.items,
+    required this.items,
   }) : super(key: key);
 
   @override
   build(BuildContext context) {
     return SimpleDialog(
-      title: title != null ? Text(title) : null,
+      title: title != null ? Text(title!) : null,
       children: items
           .map((e) => SimpleDialogOption(
                 child: ListTile(
@@ -47,6 +47,6 @@ class FancyOptionPicker extends StatelessWidget {
     );
   }
 
-  final String title;
+  final String? title;
   final List<FancyOptionPickerItem> items;
 }

lib/widget/home.dart

@@ -16,12 +16,16 @@ class HomeArguments {
 class Home extends StatefulWidget {
   static const routeName = "/home";
 
+  static Route buildRoute(HomeArguments args) => MaterialPageRoute(
+        builder: (context) => Home.fromArgs(args),
+      );
+
   Home({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  Home.fromArgs(HomeArguments args, {Key key})
+  Home.fromArgs(HomeArguments args, {Key? key})
       : this(
           account: args.account,
         );
@@ -33,12 +37,6 @@ class Home extends StatefulWidget {
 }
 
 class _HomeState extends State<Home> {
-  @override
-  initState() {
-    super.initState();
-    _pageController = PageController(initialPage: 0, keepPage: false);
-  }
-
   @override
   build(BuildContext context) {
     return AppTheme(
@@ -54,11 +52,11 @@ class _HomeState extends State<Home> {
       items: <BottomNavigationBarItem>[
         BottomNavigationBarItem(
           icon: const Icon(Icons.photo_outlined),
-          label: AppLocalizations.of(context).photosTabLabel,
+          label: AppLocalizations.of(context)!.photosTabLabel,
         ),
         BottomNavigationBarItem(
           icon: const Icon(Icons.photo_album_outlined),
-          label: AppLocalizations.of(context).albumsTabLabel,
+          label: AppLocalizations.of(context)!.albumsTabLabel,
         ),
       ],
       currentIndex: _nextPage,
@@ -108,6 +106,6 @@ class _HomeState extends State<Home> {
     });
   }
 
-  PageController _pageController;
+  final _pageController = PageController(initialPage: 0, keepPage: false);
   int _nextPage = 0;
 }

lib/widget/home_albums.dart

@@ -32,8 +32,8 @@ import 'package:tuple/tuple.dart';
 
 class HomeAlbums extends StatefulWidget {
   HomeAlbums({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
   @override
@@ -83,7 +83,7 @@ class _HomeAlbumsState extends State<HomeAlbums>
       _reqQuery();
     } else {
       // process the current state
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
         setState(() {
           _onStateChange(context, _bloc.state);
         });
@@ -149,12 +149,12 @@ class _HomeAlbumsState extends State<HomeAlbums>
             });
           },
         ),
-        title: Text(AppLocalizations.of(context)
+        title: Text(AppLocalizations.of(context)!
             .selectionAppBarTitle(_selectedItems.length)),
         actions: [
           IconButton(
             icon: const Icon(Icons.delete),
-            tooltip: AppLocalizations.of(context).deleteSelectedTooltip,
+            tooltip: AppLocalizations.of(context)!.deleteSelectedTooltip,
             onPressed: () {
               _onSelectionAppBarDeletePressed();
             },
@@ -171,13 +171,13 @@ class _HomeAlbumsState extends State<HomeAlbums>
         IconButton(
           onPressed: () => _onSearchPressed(context),
           icon: const Icon(Icons.search),
-          tooltip: AppLocalizations.of(context).searchTooltip,
+          tooltip: AppLocalizations.of(context)!.searchTooltip,
         ),
       ],
       menuActions: [
         PopupMenuItem(
           value: _menuValueImport,
-          child: Text(AppLocalizations.of(context).importFoldersTooltip),
+          child: Text(AppLocalizations.of(context)!.importFoldersTooltip),
         ),
       ],
       onSelectedMenuActions: (option) {
@@ -225,7 +225,7 @@ class _HomeAlbumsState extends State<HomeAlbums>
           ),
         ),
       ),
-      title: AppLocalizations.of(context).albumArchiveLabel,
+      title: AppLocalizations.of(context)!.albumArchiveLabel,
       onTap: () {
         Navigator.of(context).pushNamed(ArchiveViewer.routeName,
             arguments: ArchiveViewerArguments(widget.account));
@@ -247,7 +247,7 @@ class _HomeAlbumsState extends State<HomeAlbums>
           ),
         ),
       ),
-      title: AppLocalizations.of(context).createAlbumTooltip,
+      title: AppLocalizations.of(context)!.createAlbumTooltip,
       onTap: () => _onNewAlbumItemTap(context),
     );
   }
@@ -324,7 +324,7 @@ class _HomeAlbumsState extends State<HomeAlbums>
           "[_onNewAlbumItemTap] Failed while showDialog", e, stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content:
-            Text(AppLocalizations.of(context).createAlbumFailureNotification),
+            Text(AppLocalizations.of(context)!.createAlbumFailureNotification),
         duration: k.snackBarDurationNormal,
       ));
     });
@@ -337,11 +337,12 @@ class _HomeAlbumsState extends State<HomeAlbums>
 
   Future<void> _onSelectionAppBarDeletePressed() async {
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context)
+      content: Text(AppLocalizations.of(context)!
           .deleteSelectedProcessingNotification(_selectedItems.length)),
       duration: k.snackBarDurationShort,
     ));
-    final selectedFiles = _selectedItems.map((e) => e.album.albumFile).toList();
+    final selectedFiles =
+        _selectedItems.map((e) => e.album.albumFile!).toList();
     setState(() {
       _selectedItems.clear();
     });
@@ -363,12 +364,12 @@ class _HomeAlbumsState extends State<HomeAlbums>
     if (failures.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).deleteSelectedSuccessNotification),
+            AppLocalizations.of(context)!.deleteSelectedSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .deleteSelectedFailureNotification(failures.length)),
         duration: k.snackBarDurationNormal,
       ));
@@ -411,12 +412,12 @@ class _HomeAlbumsState extends State<HomeAlbums>
         .map((from) {
           try {
             return _items.whereType<_GridItem>().firstWhere(
-                (to) => from.album.albumFile.path == to.album.albumFile.path);
+                (to) => from.album.albumFile!.path == to.album.albumFile!.path);
           } catch (_) {
             return null;
           }
         })
-        .where((element) => element != null)
+        .whereType<_GridItem>()
         .toList();
     _selectedItems
       ..clear()
@@ -439,7 +440,7 @@ class _HomeAlbumsState extends State<HomeAlbums>
 
   bool get _isSelectionMode => _selectedItems.isNotEmpty;
 
-  ListAlbumBloc _bloc;
+  late ListAlbumBloc _bloc;
 
   final _items = <_GridItem>[];
   final _selectedItems = <_GridItem>[];

lib/widget/home_app_bar.dart

@@ -13,8 +13,8 @@ import 'package:nc_photos/widget/settings.dart';
 /// AppBar for home screens
 class HomeSliverAppBar extends StatelessWidget {
   HomeSliverAppBar({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
     this.actions,
     this.menuActions,
     this.onSelectedMenuActions,
@@ -90,7 +90,7 @@ class HomeSliverAppBar extends StatelessWidget {
               inactiveThumbImage:
                   const AssetImage("assets/ic_dark_mode_switch_24dp.png"),
             ),
-            PopupMenuButton(
+            PopupMenuButton<int>(
               tooltip: MaterialLocalizations.of(context).moreButtonTooltip,
               itemBuilder: (context) =>
                   (menuActions ?? []) +
@@ -98,7 +98,7 @@ class HomeSliverAppBar extends StatelessWidget {
                     PopupMenuItem(
                       value: _menuValueAbout,
                       child:
-                          Text(AppLocalizations.of(context).settingsMenuLabel),
+                          Text(AppLocalizations.of(context)!.settingsMenuLabel),
                     ),
                   ],
               onSelected: (option) {
@@ -125,12 +125,12 @@ class HomeSliverAppBar extends StatelessWidget {
   final Account account;
 
   /// Screen specific action buttons
-  final List<Widget> actions;
+  final List<Widget>? actions;
 
   /// Screen specific actions under the overflow menu. The value of each item
   /// much >= 0
-  final List<PopupMenuEntry<int>> menuActions;
+  final List<PopupMenuEntry<int>>? menuActions;
-  final void Function(int) onSelectedMenuActions;
+  final void Function(int)? onSelectedMenuActions;
 
   static const _menuValueAbout = -1;
 }

lib/widget/home_photos.dart

@@ -41,8 +41,8 @@ import 'package:nc_photos/widget/viewer.dart';
 
 class HomePhotos extends StatefulWidget {
   HomePhotos({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
   @override
@@ -59,7 +59,7 @@ class _HomePhotosState extends State<HomePhotos>
   @override
   initState() {
     super.initState();
-    _thumbZoomLevel = Pref.inst().getHomePhotosZoomLevel(0);
+    _thumbZoomLevel = Pref.inst().getHomePhotosZoomLevelOr(0);
     _initBloc();
   }
 
@@ -82,7 +82,7 @@ class _HomePhotosState extends State<HomePhotos>
       _reqQuery();
     } else {
       // process the current state
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
         setState(() {
           _onStateChange(context, _bloc.state);
         });
@@ -162,35 +162,36 @@ class _HomePhotosState extends State<HomePhotos>
             });
           },
         ),
-        title: Text(AppLocalizations.of(context)
+        title: Text(AppLocalizations.of(context)!
             .selectionAppBarTitle(selectedListItems.length)),
         actions: [
           if (platform_k.isAndroid)
             IconButton(
               icon: const Icon(Icons.share),
-              tooltip: AppLocalizations.of(context).shareSelectedTooltip,
+              tooltip: AppLocalizations.of(context)!.shareSelectedTooltip,
               onPressed: () {
                 _onSelectionAppBarSharePressed(context);
               },
             ),
           IconButton(
             icon: const Icon(Icons.playlist_add),
-            tooltip: AppLocalizations.of(context).addSelectedToAlbumTooltip,
+            tooltip: AppLocalizations.of(context)!.addSelectedToAlbumTooltip,
             onPressed: () {
               _onSelectionAppBarAddToAlbumPressed(context);
             },
           ),
-          PopupMenuButton(
+          PopupMenuButton<_SelectionAppBarMenuOption>(
             tooltip: MaterialLocalizations.of(context).moreButtonTooltip,
             itemBuilder: (context) => [
               PopupMenuItem(
                 value: _SelectionAppBarMenuOption.archive,
-                child:
+                child: Text(
-                    Text(AppLocalizations.of(context).archiveSelectedMenuLabel),
+                    AppLocalizations.of(context)!.archiveSelectedMenuLabel),
               ),
               PopupMenuItem(
                 value: _SelectionAppBarMenuOption.delete,
-                child: Text(AppLocalizations.of(context).deleteSelectedTooltip),
+                child:
+                    Text(AppLocalizations.of(context)!.deleteSelectedTooltip),
               ),
             ],
             onSelected: (option) {
@@ -212,7 +213,7 @@ class _HomePhotosState extends State<HomePhotos>
         actions: [
           PopupMenuButton(
             icon: const Icon(Icons.photo_size_select_large),
-            tooltip: AppLocalizations.of(context).zoomTooltip,
+            tooltip: AppLocalizations.of(context)!.zoomTooltip,
             itemBuilder: (context) => [
               PopupMenuZoom(
                 initialValue: _thumbZoomLevel,
@@ -231,7 +232,7 @@ class _HomePhotosState extends State<HomePhotos>
         menuActions: [
           PopupMenuItem(
             value: _menuValueRefresh,
-            child: Text(AppLocalizations.of(context).refreshMenuLabel),
+            child: Text(AppLocalizations.of(context)!.refreshMenuLabel),
           ),
         ],
         onSelectedMenuActions: (option) {
@@ -251,7 +252,7 @@ class _HomePhotosState extends State<HomePhotos>
     } else if (state is ScanDirBlocSuccess || state is ScanDirBlocLoading) {
       _transformItems(state.files);
       if (state is ScanDirBlocSuccess) {
-        if (Pref.inst().isEnableExif() && !_hasFiredMetadataTask.value) {
+        if (Pref.inst().isEnableExifOr() && !_hasFiredMetadataTask.value) {
           KiwiContainer()
               .resolve<MetadataTaskManager>()
               .addTask(MetadataTask(widget.account));
@@ -306,14 +307,14 @@ class _HomePhotosState extends State<HomePhotos>
             clearSelectedItems();
           });
           SnackBarManager().showSnackBar(SnackBar(
-            content: Text(AppLocalizations.of(context)
+            content: Text(AppLocalizations.of(context)!
                 .addSelectedToAlbumSuccessNotification(value.name)),
             duration: k.snackBarDurationNormal,
           ));
         }).catchError((_) {});
       } else {
         SnackBarManager().showSnackBar(SnackBar(
-          content: Text(AppLocalizations.of(context)
+          content: Text(AppLocalizations.of(context)!
               .addSelectedToAlbumFailureNotification),
           duration: k.snackBarDurationNormal,
         ));
@@ -325,7 +326,7 @@ class _HomePhotosState extends State<HomePhotos>
           stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            "${AppLocalizations.of(context).addSelectedToAlbumFailureNotification}: "
+            "${AppLocalizations.of(context)!.addSelectedToAlbumFailureNotification}: "
             "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -355,7 +356,7 @@ class _HomePhotosState extends State<HomePhotos>
           "[_addSelectedToAlbum] Failed while updating album", e, stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            "${AppLocalizations.of(context).addSelectedToAlbumFailureNotification}: "
+            "${AppLocalizations.of(context)!.addSelectedToAlbumFailureNotification}: "
             "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -365,7 +366,7 @@ class _HomePhotosState extends State<HomePhotos>
 
   Future<void> _onSelectionAppBarDeletePressed(BuildContext context) async {
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context)
+      content: Text(AppLocalizations.of(context)!
           .deleteSelectedProcessingNotification(selectedListItems.length)),
       duration: k.snackBarDurationShort,
     ));
@@ -394,12 +395,12 @@ class _HomePhotosState extends State<HomePhotos>
     if (failures.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).deleteSelectedSuccessNotification),
+            AppLocalizations.of(context)!.deleteSelectedSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .deleteSelectedFailureNotification(failures.length)),
         duration: k.snackBarDurationNormal,
       ));
@@ -425,7 +426,7 @@ class _HomePhotosState extends State<HomePhotos>
 
   Future<void> _onSelectionAppBarArchivePressed(BuildContext context) async {
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context)
+      content: Text(AppLocalizations.of(context)!
           .archiveSelectedProcessingNotification(selectedListItems.length)),
       duration: k.snackBarDurationShort,
     ));
@@ -454,12 +455,12 @@ class _HomePhotosState extends State<HomePhotos>
     if (failures.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            AppLocalizations.of(context).archiveSelectedSuccessNotification),
+            AppLocalizations.of(context)!.archiveSelectedSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
     } else {
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .archiveSelectedFailureNotification(failures.length)),
         duration: k.snackBarDurationNormal,
       ));
@@ -478,16 +479,16 @@ class _HomePhotosState extends State<HomePhotos>
             file_util.isSupportedFormat(element) && element.isArchived != true)
         .sorted(compareFileDateTimeDescending);
 
-    DateTime currentDate;
+    DateTime? currentDate;
     final isMonthOnly = _thumbZoomLevel < 0;
     itemStreamListItems = () sync* {
       for (int i = 0; i < _backingFiles.length; ++i) {
         final f = _backingFiles[i];
 
-        final newDate = f.bestDateTime?.toLocal();
+        final newDate = f.bestDateTime.toLocal();
-        if (newDate?.year != currentDate?.year ||
+        if (newDate.year != currentDate?.year ||
-            newDate?.month != currentDate?.month ||
+            newDate.month != currentDate?.month ||
-            (!isMonthOnly && newDate?.day != currentDate?.day)) {
+            (!isMonthOnly && newDate.day != currentDate?.day)) {
           yield _DateListItem(date: newDate, isMonthOnly: isMonthOnly);
           currentDate = newDate;
         }
@@ -546,13 +547,13 @@ class _HomePhotosState extends State<HomePhotos>
   }
 
   /// Return the estimated scroll extent of the custom scroll view, or null
-  double _getScrollViewExtent(BoxConstraints constraints) {
+  double? _getScrollViewExtent(BoxConstraints constraints) {
     if (_itemListMaxExtent != null &&
         constraints.hasBoundedHeight &&
         _appBarExtent != null) {
       // scroll extent = list height - widget viewport height + sliver app bar height + list padding
       final scrollExtent =
-          _itemListMaxExtent - constraints.maxHeight + _appBarExtent + 16;
+          _itemListMaxExtent! - constraints.maxHeight + _appBarExtent! + 16;
       _log.info(
           "[_getScrollViewExtent] $_itemListMaxExtent - ${constraints.maxHeight} + $_appBarExtent + 16 = $scrollExtent");
       return scrollExtent;
@@ -595,7 +596,7 @@ class _HomePhotosState extends State<HomePhotos>
     }
   }
 
-  ScanDirBloc _bloc;
+  late ScanDirBloc _bloc;
 
   var _backingFiles = <File>[];
 
@@ -603,8 +604,8 @@ class _HomePhotosState extends State<HomePhotos>
 
   final ScrollController _scrollController = ScrollController();
 
-  double _appBarExtent;
+  double? _appBarExtent;
-  double _itemListMaxExtent;
+  double? _itemListMaxExtent;
 
   static final _log = Logger("widget.home_photos._HomePhotosState");
   static const _menuValueRefresh = 0;
@@ -612,7 +613,7 @@ class _HomePhotosState extends State<HomePhotos>
 
 abstract class _ListItem implements SelectableItem {
   _ListItem({
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : _onTap = onTap;
 
   @override
@@ -624,12 +625,12 @@ abstract class _ListItem implements SelectableItem {
   @override
   get staggeredTile => const StaggeredTile.count(1, 1);
 
-  final VoidCallback _onTap;
+  final VoidCallback? _onTap;
 }
 
 class _DateListItem extends _ListItem {
   _DateListItem({
-    @required this.date,
+    required this.date,
     this.isMonthOnly = false,
   });
 
@@ -647,7 +648,7 @@ class _DateListItem extends _ListItem {
           isMonthOnly ? DateFormat.YEAR_MONTH : DateFormat.YEAR_MONTH_DAY;
       subtitle =
           DateFormat(pattern, Localizations.localeOf(context).languageCode)
-              .format(date.toLocal());
+              .format(date!.toLocal());
     }
     return Align(
       alignment: AlignmentDirectional.centerStart,
@@ -655,7 +656,7 @@ class _DateListItem extends _ListItem {
         padding: const EdgeInsets.symmetric(horizontal: 8),
         child: Text(
           subtitle,
-          style: Theme.of(context).textTheme.caption.copyWith(
+          style: Theme.of(context).textTheme.caption!.copyWith(
                 color: AppTheme.getPrimaryTextColor(context),
                 fontWeight: FontWeight.bold,
               ),
@@ -664,14 +665,14 @@ class _DateListItem extends _ListItem {
     );
   }
 
-  final DateTime date;
+  final DateTime? date;
   final bool isMonthOnly;
 }
 
 abstract class _FileListItem extends _ListItem {
   _FileListItem({
-    @required this.file,
+    required this.file,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(onTap: onTap);
 
   @override
@@ -687,10 +688,10 @@ abstract class _FileListItem extends _ListItem {
 
 class _ImageListItem extends _FileListItem {
   _ImageListItem({
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(file: file, onTap: onTap);
 
   @override
@@ -708,10 +709,10 @@ class _ImageListItem extends _FileListItem {
 
 class _VideoListItem extends _FileListItem {
   _VideoListItem({
-    @required File file,
+    required File file,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
-    VoidCallback onTap,
+    VoidCallback? onTap,
   }) : super(file: file, onTap: onTap);
 
   @override

lib/widget/image_viewer.dart

@@ -11,9 +11,9 @@ import 'package:nc_photos/widget/cached_network_image_mod.dart' as mod;
 
 class ImageViewer extends StatefulWidget {
   ImageViewer({
-    @required this.account,
+    required this.account,
-    @required this.file,
+    required this.file,
-    this.canZoom,
+    required this.canZoom,
     this.onLoaded,
     this.onHeightChanged,
     this.onZoomStarted,
@@ -35,10 +35,10 @@ class ImageViewer extends StatefulWidget {
   final Account account;
   final File file;
   final bool canZoom;
-  final VoidCallback onLoaded;
+  final VoidCallback? onLoaded;
-  final void Function(double height) onHeightChanged;
+  final ValueChanged<double>? onHeightChanged;
-  final VoidCallback onZoomStarted;
+  final VoidCallback? onZoomStarted;
-  final VoidCallback onZoomEnded;
+  final VoidCallback? onZoomEnded;
 }
 
 class _ImageViewerState extends State<ImageViewer>
@@ -58,9 +58,9 @@ class _ImageViewerState extends State<ImageViewer>
         alignment: Alignment.center,
         child: NotificationListener<SizeChangedLayoutNotification>(
           onNotification: (_) {
-            WidgetsBinding.instance.addPostFrameCallback((_) {
+            WidgetsBinding.instance!.addPostFrameCallback((_) {
               if (_key.currentContext != null) {
-                widget.onHeightChanged?.call(_key.currentContext.size.height);
+                widget.onHeightChanged?.call(_key.currentContext!.size!.height);
               }
             });
             return false;
@@ -78,7 +78,7 @@ class _ImageViewerState extends State<ImageViewer>
               filterQuality: FilterQuality.high,
               imageRenderMethodForWeb: ImageRenderMethodForWeb.HttpGet,
               imageBuilder: (context, child, imageProvider) {
-                WidgetsBinding.instance.addPostFrameCallback((_) {
+                WidgetsBinding.instance!.addPostFrameCallback((_) {
                   _onItemLoaded();
                 });
                 SizeChangedLayoutNotification().dispatch(context);

lib/widget/measurable_item_list.dart

@@ -10,11 +10,11 @@ abstract class MeasurableItemListState {
 
 class MeasurableItemList extends StatefulWidget {
   MeasurableItemList({
-    Key key,
+    Key? key,
-    @required this.maxCrossAxisExtent,
+    required this.maxCrossAxisExtent,
-    @required this.itemCount,
+    required this.itemCount,
-    @required this.itemBuilder,
+    required this.itemBuilder,
-    @required this.staggeredTileBuilder,
+    required this.staggeredTileBuilder,
     this.onMaxExtentChanged,
   }) : super(key: key);
 
@@ -25,7 +25,7 @@ class MeasurableItemList extends StatefulWidget {
   final int itemCount;
   final IndexedWidgetBuilder itemBuilder;
   final IndexedStaggeredTileBuilder staggeredTileBuilder;
-  final ValueChanged<double> onMaxExtentChanged;
+  final ValueChanged<double?>? onMaxExtentChanged;
 }
 
 class _MeasurableItemListState extends State<MeasurableItemList>
@@ -35,21 +35,21 @@ class _MeasurableItemListState extends State<MeasurableItemList>
   initState() {
     super.initState();
 
-    WidgetsBinding.instance.addPostFrameCallback((_) {
+    WidgetsBinding.instance!.addPostFrameCallback((_) {
       _prevOrientation = MediaQuery.of(context).orientation;
-      WidgetsBinding.instance.addObserver(this);
+      WidgetsBinding.instance!.addObserver(this);
     });
   }
 
   @override
   dispose() {
-    WidgetsBinding.instance.removeObserver(this);
+    WidgetsBinding.instance!.removeObserver(this);
     super.dispose();
   }
 
   @override
   didChangeMetrics() {
-    WidgetsBinding.instance.addPostFrameCallback((_) {
+    WidgetsBinding.instance!.addPostFrameCallback((_) {
       final orientation = MediaQuery.of(context).orientation;
       if (orientation != _prevOrientation) {
         _log.info(
@@ -70,7 +70,8 @@ class _MeasurableItemListState extends State<MeasurableItemList>
       }
       if (constraints.crossAxisExtent != _prevListWidth) {
         _log.info("[build] updateListHeight: list viewport width changed");
-        WidgetsBinding.instance.addPostFrameCallback((_) => updateListHeight());
+        WidgetsBinding.instance!
+            .addPostFrameCallback((_) => updateListHeight());
         _prevListWidth = constraints.crossAxisExtent;
       }
 
@@ -78,7 +79,8 @@ class _MeasurableItemListState extends State<MeasurableItemList>
       final cellSize = widget.maxCrossAxisExtent;
       if (cellSize != _prevCellSize) {
         _log.info("[build] updateListHeight: cell size changed");
-        WidgetsBinding.instance.addPostFrameCallback((_) => updateListHeight());
+        WidgetsBinding.instance!
+            .addPostFrameCallback((_) => updateListHeight());
         _prevCellSize = cellSize;
       }
       _gridKey = _GridKey("$_uniqueToken $cellSize");
@@ -94,9 +96,9 @@ class _MeasurableItemListState extends State<MeasurableItemList>
 
   @override
   updateListHeight() {
-    double newMaxExtent;
+    double? newMaxExtent;
     try {
-      final renderObj = _gridKey.currentContext.findRenderObject()
+      final renderObj = _gridKey.currentContext!.findRenderObject()
           as RenderMeasurableSliverStaggeredGrid;
       final maxExtent = renderObj.calculateExtent();
       _log.info("[updateListHeight] Max extent: $maxExtent");
@@ -118,14 +120,14 @@ class _MeasurableItemListState extends State<MeasurableItemList>
     }
   }
 
-  double _prevListWidth;
+  double? _prevListWidth;
-  double _prevCellSize;
+  double? _prevCellSize;
-  double _maxExtent;
+  double? _maxExtent;
-  Orientation _prevOrientation;
+  Orientation? _prevOrientation;
 
   // this unique token is there to keep the global key unique
   final _uniqueToken = Uuid().v4();
-  GlobalObjectKey _gridKey;
+  late GlobalObjectKey _gridKey;
 
   static final _log =
       Logger("widget.measurable_item_list._MeasurableItemListState");

lib/widget/measure.dart

@@ -8,9 +8,9 @@ class MeasureSize extends SingleChildRenderObjectWidget {
   final OnWidgetSizeChanged onChange;
 
   const MeasureSize({
-    Key key,
+    Key? key,
-    @required this.onChange,
+    required this.onChange,
-    @required Widget child,
+    required Widget child,
   }) : super(key: key, child: child);
 
   @override
@@ -20,7 +20,7 @@ class MeasureSize extends SingleChildRenderObjectWidget {
 }
 
 class _MeasureSizeRenderObject extends RenderProxyBox {
-  Size oldSize;
+  Size? oldSize;
   final OnWidgetSizeChanged onChange;
 
   _MeasureSizeRenderObject(this.onChange);
@@ -29,11 +29,11 @@ class _MeasureSizeRenderObject extends RenderProxyBox {
   void performLayout() {
     super.performLayout();
 
-    Size newSize = child.size;
+    var newSize = child?.size;
-    if (oldSize == newSize) return;
+    if (newSize == null || oldSize == newSize) return;
 
     oldSize = newSize;
-    WidgetsBinding.instance.addPostFrameCallback((_) {
+    WidgetsBinding.instance!.addPostFrameCallback((_) {
       onChange(newSize);
     });
   }
@@ -41,9 +41,9 @@ class _MeasureSizeRenderObject extends RenderProxyBox {
 
 class SliverMeasureExtent extends SingleChildRenderObjectWidget {
   const SliverMeasureExtent({
-    Key key,
+    Key? key,
-    @required this.onChange,
+    required this.onChange,
-    @required Widget child,
+    required Widget child,
   }) : super(key: key, child: child);
 
   @override
@@ -61,16 +61,16 @@ class _SliverMeasureExtentRenderObject extends RenderProxySliver {
   void performLayout() {
     super.performLayout();
 
-    double newExent = child.geometry.scrollExtent;
+    var newExent = child?.geometry?.scrollExtent;
-    if (_oldExtent == newExent) {
+    if (newExent == null || _oldExtent == newExent) {
       return;
     }
 
     _oldExtent = newExent;
-    WidgetsBinding.instance.addPostFrameCallback((_) => onChange(newExent));
+    WidgetsBinding.instance!.addPostFrameCallback((_) => onChange(newExent));
   }
 
   final void Function(double) onChange;
 
-  double _oldExtent;
+  double? _oldExtent;
 }

lib/widget/measureable_sliver_staggered_grid.dart

@@ -5,11 +5,11 @@ import 'package:flutter_staggered_grid_view/flutter_staggered_grid_view.dart';
 // ignore: must_be_immutable
 class MeasurableSliverStaggeredGrid extends SliverStaggeredGrid {
   MeasurableSliverStaggeredGrid.extentBuilder({
-    Key key,
+    Key? key,
-    @required double maxCrossAxisExtent,
+    required double maxCrossAxisExtent,
-    @required IndexedStaggeredTileBuilder staggeredTileBuilder,
+    required IndexedStaggeredTileBuilder staggeredTileBuilder,
-    @required IndexedWidgetBuilder itemBuilder,
+    required IndexedWidgetBuilder itemBuilder,
-    @required int itemCount,
+    required int itemCount,
     double mainAxisSpacing = 0,
     double crossAxisSpacing = 0,
   }) : super(
@@ -32,19 +32,19 @@ class MeasurableSliverStaggeredGrid extends SliverStaggeredGrid {
     final element = context as SliverVariableSizeBoxAdaptorElement;
     _renderObject = RenderMeasurableSliverStaggeredGrid(
         childManager: element, gridDelegate: gridDelegate);
-    return _renderObject;
+    return _renderObject!;
   }
 
-  RenderMeasurableSliverStaggeredGrid get renderObject => _renderObject;
+  RenderMeasurableSliverStaggeredGrid? get renderObject => _renderObject;
 
-  RenderMeasurableSliverStaggeredGrid _renderObject;
+  RenderMeasurableSliverStaggeredGrid? _renderObject;
 }
 
 class RenderMeasurableSliverStaggeredGrid extends RenderSliverStaggeredGrid
     with WidgetsBindingObserver {
   RenderMeasurableSliverStaggeredGrid({
-    @required RenderSliverVariableSizeBoxChildManager childManager,
+    required RenderSliverVariableSizeBoxChildManager childManager,
-    @required SliverStaggeredGridDelegate gridDelegate,
+    required SliverStaggeredGridDelegate gridDelegate,
   }) : super(childManager: childManager, gridDelegate: gridDelegate);
 
   /// Calculate the height of this staggered grid view
@@ -69,13 +69,13 @@ class RenderMeasurableSliverStaggeredGrid extends RenderSliverStaggeredGrid
       }
 
       final bool hasTrailingScrollOffset = geometry.hasTrailingScrollOffset;
-      RenderBox child;
+      RenderBox? child;
       if (!hasTrailingScrollOffset) {
         // Layout the child to compute its tailingScrollOffset.
         final constraints =
             BoxConstraints.tightFor(width: geometry.crossAxisExtent);
         child = addAndLayoutChild(index, constraints, parentUsesSize: true);
-        geometry = geometry.copyWith(mainAxisExtent: paintExtentOf(child));
+        geometry = geometry.copyWith(mainAxisExtent: paintExtentOf(child!));
       }
 
       if (child != null) {

lib/widget/my_app.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import 'package:logging/logging.dart';
+import 'package:nc_photos/account.dart';
 import 'package:nc_photos/event/event.dart';
 import 'package:nc_photos/language_util.dart' as language_util;
 import 'package:nc_photos/pref.dart';
@@ -44,10 +45,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
   @override
   build(BuildContext context) {
     return MaterialApp(
-      onGenerateTitle: (context) => AppLocalizations.of(context).appTitle,
+      onGenerateTitle: (context) => AppLocalizations.of(context)!.appTitle,
       theme: _getLightTheme(),
       darkTheme: _getDarkTheme(),
-      themeMode: Pref.inst().isDarkTheme() ? ThemeMode.dark : ThemeMode.light,
+      themeMode:
+          Pref.inst().isDarkThemeOr(false) ? ThemeMode.dark : ThemeMode.light,
       initialRoute: Splash.routeName,
       onGenerateRoute: _onGenerateRoute,
       navigatorObservers: <NavigatorObserver>[MyApp.routeObserver],
@@ -87,9 +89,9 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
         Splash.routeName: (context) => Splash(),
       };
 
-  Route<dynamic> _onGenerateRoute(RouteSettings settings) {
+  Route<dynamic>? _onGenerateRoute(RouteSettings settings) {
     _log.info("[_onGenerateRoute] Route: ${settings.name}");
-    Route<dynamic> route;
+    Route<dynamic>? route;
     route ??= _handleBasicRoute(settings);
     route ??= _handleViewerRoute(settings);
     route ??= _handleConnectRoute(settings);
@@ -112,7 +114,7 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     setState(() {});
   }
 
-  Route<dynamic> _handleBasicRoute(RouteSettings settings) {
+  Route<dynamic>? _handleBasicRoute(RouteSettings settings) {
     for (final e in _getRouter().entries) {
       if (e.key == settings.name) {
         return MaterialPageRoute(
@@ -123,13 +125,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleViewerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleViewerRoute(RouteSettings settings) {
     try {
       if (settings.name == Viewer.routeName && settings.arguments != null) {
-        final ViewerArguments args = settings.arguments;
+        final args = settings.arguments as ViewerArguments;
-        return MaterialPageRoute(
+        return Viewer.buildRoute(args);
-          builder: (context) => Viewer.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleViewerRoute] Failed while handling route", e);
@@ -137,13 +137,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleConnectRoute(RouteSettings settings) {
+  Route<dynamic>? _handleConnectRoute(RouteSettings settings) {
     try {
       if (settings.name == Connect.routeName && settings.arguments != null) {
-        final ConnectArguments args = settings.arguments;
+        final args = settings.arguments as ConnectArguments;
-        return MaterialPageRoute(
+        return Connect.buildRoute(args);
-          builder: (context) => Connect.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleConnectRoute] Failed while handling route", e);
@@ -151,13 +149,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleHomeRoute(RouteSettings settings) {
+  Route<dynamic>? _handleHomeRoute(RouteSettings settings) {
     try {
       if (settings.name == Home.routeName && settings.arguments != null) {
-        final HomeArguments args = settings.arguments;
+        final args = settings.arguments as HomeArguments;
-        return MaterialPageRoute(
+        return Home.buildRoute(args);
-          builder: (context) => Home.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleHomeRoute] Failed while handling route", e);
@@ -165,13 +161,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleRootPickerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleRootPickerRoute(RouteSettings settings) {
     try {
       if (settings.name == RootPicker.routeName && settings.arguments != null) {
-        final RootPickerArguments args = settings.arguments;
+        final args = settings.arguments as RootPickerArguments;
-        return MaterialPageRoute(
+        return RootPicker.buildRoute(args);
-          builder: (context) => RootPicker.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleRootPickerRoute] Failed while handling route", e);
@@ -179,14 +173,12 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleAlbumViewerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleAlbumViewerRoute(RouteSettings settings) {
     try {
       if (settings.name == AlbumViewer.routeName &&
           settings.arguments != null) {
-        final AlbumViewerArguments args = settings.arguments;
+        final args = settings.arguments as AlbumViewerArguments;
-        return MaterialPageRoute(
+        return AlbumViewer.buildRoute(args);
-          builder: (context) => AlbumViewer.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleAlbumViewerRoute] Failed while handling route", e);
@@ -194,13 +186,11 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleSettingsRoute(RouteSettings settings) {
+  Route<dynamic>? _handleSettingsRoute(RouteSettings settings) {
     try {
       if (settings.name == Settings.routeName && settings.arguments != null) {
-        final SettingsArguments args = settings.arguments;
+        final args = settings.arguments as SettingsArguments;
-        return MaterialPageRoute(
+        return Settings.buildRoute(args);
-          builder: (context) => Settings.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleSettingsRoute] Failed while handling route", e);
@@ -208,14 +198,12 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleArchiveViewerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleArchiveViewerRoute(RouteSettings settings) {
     try {
       if (settings.name == ArchiveViewer.routeName &&
           settings.arguments != null) {
-        final ArchiveViewerArguments args = settings.arguments;
+        final args = settings.arguments as ArchiveViewerArguments;
-        return MaterialPageRoute(
+        return ArchiveViewer.buildRoute(args);
-          builder: (context) => ArchiveViewer.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleArchiveViewerRoute] Failed while handling route", e);
@@ -223,14 +211,12 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleDynamicAlbumViewerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleDynamicAlbumViewerRoute(RouteSettings settings) {
     try {
       if (settings.name == DynamicAlbumViewer.routeName &&
           settings.arguments != null) {
-        final DynamicAlbumViewerArguments args = settings.arguments;
+        final args = settings.arguments as DynamicAlbumViewerArguments;
-        return MaterialPageRoute(
+        return DynamicAlbumViewer.buildRoute(args);
-          builder: (context) => DynamicAlbumViewer.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe(
@@ -239,14 +225,12 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleAlbumDirPickerRoute(RouteSettings settings) {
+  Route<dynamic>? _handleAlbumDirPickerRoute(RouteSettings settings) {
     try {
       if (settings.name == AlbumDirPicker.routeName &&
           settings.arguments != null) {
-        final AlbumDirPickerArguments args = settings.arguments;
+        final args = settings.arguments as AlbumDirPickerArguments;
-        return MaterialPageRoute(
+        return AlbumDirPicker.buildRoute(args);
-          builder: (context) => AlbumDirPicker.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe(
@@ -255,14 +239,12 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
     return null;
   }
 
-  Route<dynamic> _handleAlbumImporterRoute(RouteSettings settings) {
+  Route<dynamic>? _handleAlbumImporterRoute(RouteSettings settings) {
     try {
       if (settings.name == AlbumImporter.routeName &&
           settings.arguments != null) {
-        final AlbumImporterArguments args = settings.arguments;
+        final args = settings.arguments as AlbumImporterArguments;
-        return MaterialPageRoute(
+        return AlbumImporter.buildRoute(args);
-          builder: (context) => AlbumImporter.fromArgs(args),
-        );
       }
     } catch (e) {
       _log.severe("[_handleAlbumImporterRoute] Failed while handling route", e);
@@ -272,8 +254,8 @@ class _MyAppState extends State<MyApp> implements SnackBarHandler {
 
   final _scaffoldMessengerKey = GlobalKey<ScaffoldMessengerState>();
 
-  AppEventListener<ThemeChangedEvent> _themeChangedListener;
+  late AppEventListener<ThemeChangedEvent> _themeChangedListener;
-  AppEventListener<LanguageChangedEvent> _langChangedListener;
+  late AppEventListener<LanguageChangedEvent> _langChangedListener;
 
   static final _log = Logger("widget.my_app.MyAppState");
 }

lib/widget/new_album_dialog.dart

@@ -7,6 +7,7 @@ import 'package:nc_photos/entity/album.dart';
 import 'package:nc_photos/entity/album/cover_provider.dart';
 import 'package:nc_photos/entity/album/provider.dart';
 import 'package:nc_photos/entity/album/sort_provider.dart';
+import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/use_case/create_album.dart';
 import 'package:nc_photos/widget/album_dir_picker.dart';
 
@@ -16,8 +17,8 @@ import 'package:nc_photos/widget/album_dir_picker.dart';
 /// cancelled
 class NewAlbumDialog extends StatefulWidget {
   NewAlbumDialog({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
     this.isAllowDynamic = true,
   }) : super(key: key);
 
@@ -39,7 +40,7 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
     return Visibility(
       visible: _isVisible,
       child: AlertDialog(
-        title: Text(AppLocalizations.of(context).createAlbumTooltip),
+        title: Text(AppLocalizations.of(context)!.createAlbumTooltip),
         content: Form(
           key: _formKey,
           child: Container(
@@ -50,17 +51,17 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
               children: [
                 TextFormField(
                   decoration: InputDecoration(
-                    hintText: AppLocalizations.of(context).nameInputHint,
+                    hintText: AppLocalizations.of(context)!.nameInputHint,
                   ),
                   validator: (value) {
-                    if (value.isEmpty) {
+                    if (value!.isEmpty) {
-                      return AppLocalizations.of(context)
+                      return AppLocalizations.of(context)!
                           .albumNameInputInvalidEmpty;
                     }
                     return null;
                   },
                   onSaved: (value) {
-                    _formValue.name = value;
+                    _formValue.name = value!;
                   },
                 ),
                 if (widget.isAllowDynamic) ...[
@@ -75,7 +76,7 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
                           .toList(),
                       onChanged: (newValue) {
                         setState(() {
-                          _provider = newValue;
+                          _provider = newValue!;
                         });
                       },
                       onSaved: (value) {
@@ -104,8 +105,8 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
   }
 
   void _onOkPressed(BuildContext context) {
-    if (_formKey.currentState.validate()) {
+    if (_formKey.currentState?.validate() == true) {
-      _formKey.currentState.save();
+      _formKey.currentState!.save();
       if (_formValue.provider == _Provider.static ||
           _formValue.provider == null) {
         _onConfirmStaticAlbum();
@@ -136,7 +137,7 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
       _isVisible = false;
     });
     Navigator.of(context)
-        .pushNamed(AlbumDirPicker.routeName,
+        .pushNamed<List<File>>(AlbumDirPicker.routeName,
             arguments: AlbumDirPickerArguments(widget.account))
         .then((value) {
       if (value == null) {
@@ -174,8 +175,8 @@ class _NewAlbumDialogState extends State<NewAlbumDialog> {
 }
 
 class _FormValue {
-  String name;
+  late String name;
-  _Provider provider;
+  _Provider? provider;
 }
 
 enum _Provider {
@@ -187,10 +188,10 @@ extension on _Provider {
   String toValueString(BuildContext context) {
     switch (this) {
       case _Provider.static:
-        return AppLocalizations.of(context).createAlbumDialogBasicLabel;
+        return AppLocalizations.of(context)!.createAlbumDialogBasicLabel;
 
       case _Provider.dir:
-        return AppLocalizations.of(context).createAlbumDialogFolderBasedLabel;
+        return AppLocalizations.of(context)!.createAlbumDialogFolderBasedLabel;
 
       default:
         throw StateError("Unknown value: $this");
@@ -200,10 +201,10 @@ extension on _Provider {
   String toDescription(BuildContext context) {
     switch (this) {
       case _Provider.static:
-        return AppLocalizations.of(context).createAlbumDialogBasicDescription;
+        return AppLocalizations.of(context)!.createAlbumDialogBasicDescription;
 
       case _Provider.dir:
-        return AppLocalizations.of(context)
+        return AppLocalizations.of(context)!
             .createAlbumDialogFolderBasedDescription;
 
       default:

lib/widget/page_visibility_mixin.dart

@@ -5,7 +5,7 @@ mixin PageVisibilityMixin<T extends StatefulWidget> on State<T>, RouteAware {
   @override
   didChangeDependencies() {
     super.didChangeDependencies();
-    MyApp.routeObserver.subscribe(this, ModalRoute.of(context));
+    MyApp.routeObserver.subscribe(this, ModalRoute.of(context)!);
   }
 
   @override

lib/widget/photo_date_time_edit_dialog.dart

@@ -6,8 +6,8 @@ import 'package:nc_photos/num_extension.dart';
 
 class PhotoDateTimeEditDialog extends StatefulWidget {
   PhotoDateTimeEditDialog({
-    Key key,
+    Key? key,
-    @required this.initialDateTime,
+    required this.initialDateTime,
   }) : super(key: key);
 
   @override
@@ -20,7 +20,7 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
   @override
   build(BuildContext context) {
     return AlertDialog(
-      title: Text(AppLocalizations.of(context).updateDateTimeDialogTitle),
+      title: Text(AppLocalizations.of(context)!.updateDateTimeDialogTitle),
       content: Form(
         key: _formKey,
         child: Container(
@@ -29,7 +29,7 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
             mainAxisSize: MainAxisSize.min,
             children: [
               Text(
-                AppLocalizations.of(context).dateSubtitle,
+                AppLocalizations.of(context)!.dateSubtitle,
                 style: Theme.of(context).textTheme.subtitle2,
               ),
               Row(
@@ -38,20 +38,20 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
                     child: TextFormField(
                       decoration: InputDecoration(
                         hintText:
-                            AppLocalizations.of(context).dateYearInputHint,
+                            AppLocalizations.of(context)!.dateYearInputHint,
                       ),
                       keyboardType: TextInputType.number,
                       validator: (value) {
                         try {
-                          int.parse(value);
+                          int.parse(value!);
                           return null;
                         } catch (_) {
-                          return AppLocalizations.of(context)
+                          return AppLocalizations.of(context)!
                               .dateTimeInputInvalid;
                         }
                       },
                       onSaved: (value) {
-                        _formValue.year = int.parse(value);
+                        _formValue.year = int.parse(value!);
                       },
                       initialValue: "${widget.initialDateTime.year}",
                     ),
@@ -62,18 +62,18 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
                     child: TextFormField(
                       decoration: InputDecoration(
                         hintText:
-                            AppLocalizations.of(context).dateMonthInputHint,
+                            AppLocalizations.of(context)!.dateMonthInputHint,
                       ),
                       keyboardType: TextInputType.number,
                       validator: (value) {
-                        if (int.tryParse(value)?.inRange(1, 12) == true) {
+                        if (int.tryParse(value!)?.inRange(1, 12) == true) {
                           return null;
                         }
-                        return AppLocalizations.of(context)
+                        return AppLocalizations.of(context)!
                             .dateTimeInputInvalid;
                       },
                       onSaved: (value) {
-                        _formValue.month = int.parse(value);
+                        _formValue.month = int.parse(value!);
                       },
                       initialValue: widget.initialDateTime.month
                           .toString()
@@ -85,18 +85,19 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
                   Flexible(
                     child: TextFormField(
                       decoration: InputDecoration(
-                        hintText: AppLocalizations.of(context).dateDayInputHint,
+                        hintText:
+                            AppLocalizations.of(context)!.dateDayInputHint,
                       ),
                       keyboardType: TextInputType.number,
                       validator: (value) {
-                        if (int.tryParse(value)?.inRange(1, 31) == true) {
+                        if (int.tryParse(value!)?.inRange(1, 31) == true) {
                           return null;
                         }
-                        return AppLocalizations.of(context)
+                        return AppLocalizations.of(context)!
                             .dateTimeInputInvalid;
                       },
                       onSaved: (value) {
-                        _formValue.day = int.parse(value);
+                        _formValue.day = int.parse(value!);
                       },
                       initialValue:
                           widget.initialDateTime.day.toString().padLeft(2, "0"),
@@ -107,7 +108,7 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
               ),
               const SizedBox(height: 16),
               Text(
-                AppLocalizations.of(context).timeSubtitle,
+                AppLocalizations.of(context)!.timeSubtitle,
                 style: Theme.of(context).textTheme.subtitle2,
               ),
               Row(
@@ -116,18 +117,18 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
                     child: TextFormField(
                       decoration: InputDecoration(
                         hintText:
-                            AppLocalizations.of(context).timeHourInputHint,
+                            AppLocalizations.of(context)!.timeHourInputHint,
                       ),
                       keyboardType: TextInputType.number,
                       validator: (value) {
-                        if (int.tryParse(value)?.inRange(0, 23) == true) {
+                        if (int.tryParse(value!)?.inRange(0, 23) == true) {
                           return null;
                         }
-                        return AppLocalizations.of(context)
+                        return AppLocalizations.of(context)!
                             .dateTimeInputInvalid;
                       },
                       onSaved: (value) {
-                        _formValue.hour = int.parse(value);
+                        _formValue.hour = int.parse(value!);
                       },
                       initialValue: widget.initialDateTime.hour
                           .toString()
@@ -140,18 +141,18 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
                     child: TextFormField(
                       decoration: InputDecoration(
                         hintText:
-                            AppLocalizations.of(context).timeMinuteInputHint,
+                            AppLocalizations.of(context)!.timeMinuteInputHint,
                       ),
                       keyboardType: TextInputType.number,
                       validator: (value) {
-                        if (int.tryParse(value)?.inRange(0, 59) == true) {
+                        if (int.tryParse(value!)?.inRange(0, 59) == true) {
                           return null;
                         }
-                        return AppLocalizations.of(context)
+                        return AppLocalizations.of(context)!
                             .dateTimeInputInvalid;
                       },
                       onSaved: (value) {
-                        _formValue.minute = int.parse(value);
+                        _formValue.minute = int.parse(value!);
                       },
                       initialValue: widget.initialDateTime.minute
                           .toString()
@@ -180,8 +181,8 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
   }
 
   void _onSavePressed(BuildContext context) {
-    if (_formKey.currentState.validate()) {
+    if (_formKey.currentState?.validate() == true) {
-      _formKey.currentState.save();
+      _formKey.currentState!.save();
       final d = DateTime(_formValue.year, _formValue.month, _formValue.day,
           _formValue.hour, _formValue.minute);
       _log.info("[_onSavePressed] Set date time: $d");
@@ -197,9 +198,9 @@ class _PhotoDateTimeEditDialogState extends State<PhotoDateTimeEditDialog> {
 }
 
 class _FormValue {
-  int year;
+  late int year;
-  int month;
+  late int month;
-  int day;
+  late int day;
-  int hour;
+  late int hour;
-  int minute;
+  late int minute;
 }

lib/widget/photo_list_item.dart

@@ -7,9 +7,9 @@ import 'package:nc_photos/theme.dart';
 
 class PhotoListImage extends StatelessWidget {
   const PhotoListImage({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
     this.isGif = false,
   }) : super(key: key);
 
@@ -72,9 +72,9 @@ class PhotoListImage extends StatelessWidget {
 
 class PhotoListVideo extends StatelessWidget {
   const PhotoListVideo({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.previewUrl,
+    required this.previewUrl,
   }) : super(key: key);
 
   @override

lib/widget/popup_menu_zoom.dart

@@ -2,10 +2,10 @@ import 'package:flutter/material.dart';
 
 class PopupMenuZoom extends PopupMenuEntry<void> {
   PopupMenuZoom({
-    Key key,
+    Key? key,
-    @required this.initialValue,
+    required this.initialValue,
-    @required this.minValue,
+    required this.minValue,
-    @required this.maxValue,
+    required this.maxValue,
     this.onChanged,
   }) : super(key: key);
 
@@ -22,7 +22,7 @@ class PopupMenuZoom extends PopupMenuEntry<void> {
   final int initialValue;
   final double minValue;
   final double maxValue;
-  final void Function(double) onChanged;
+  final void Function(double)? onChanged;
 }
 
 class _PopupMenuZoomState extends State<PopupMenuZoom> {

lib/widget/processing_dialog.dart

@@ -3,8 +3,8 @@ import 'package:flutter/widgets.dart';
 
 class ProcessingDialog extends StatelessWidget {
   ProcessingDialog({
-    Key key,
+    Key? key,
-    @required this.text,
+    required this.text,
   });
 
   @override

lib/widget/root_picker.dart

@@ -25,12 +25,17 @@ class RootPickerArguments {
 class RootPicker extends StatefulWidget {
   static const routeName = "/root-picker";
 
+  static Route buildRoute(RootPickerArguments args) =>
+      MaterialPageRoute<Account>(
+        builder: (context) => RootPicker.fromArgs(args),
+      );
+
   RootPicker({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  RootPicker.fromArgs(RootPickerArguments args, {Key key})
+  RootPicker.fromArgs(RootPickerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -100,7 +105,7 @@ class _RootPickerState extends State<RootPicker>
             child: Column(
               children: [
                 Text(
-                  AppLocalizations.of(context).rootPickerHeaderText,
+                  AppLocalizations.of(context)!.rootPickerHeaderText,
                   style: Theme.of(context).textTheme.headline5,
                   textAlign: TextAlign.center,
                 ),
@@ -108,7 +113,7 @@ class _RootPickerState extends State<RootPicker>
                 Align(
                   alignment: AlignmentDirectional.topStart,
                   child: Text(
-                    AppLocalizations.of(context).rootPickerSubHeaderText,
+                    AppLocalizations.of(context)!.rootPickerSubHeaderText,
                   ),
                 ),
               ],
@@ -127,11 +132,11 @@ class _RootPickerState extends State<RootPicker>
               children: [
                 TextButton(
                   onPressed: () => _onSkipPressed(context),
-                  child: Text(AppLocalizations.of(context).skipButtonLabel),
+                  child: Text(AppLocalizations.of(context)!.skipButtonLabel),
                 ),
                 ElevatedButton(
                   onPressed: () => _onConfirmPressed(context),
-                  child: Text(AppLocalizations.of(context).confirmButtonLabel),
+                  child: Text(AppLocalizations.of(context)!.confirmButtonLabel),
                 ),
               ],
             ),
@@ -145,7 +150,7 @@ class _RootPickerState extends State<RootPicker>
     showDialog(
         context: context,
         builder: (context) => AlertDialog(
-              content: Text(AppLocalizations.of(context)
+              content: Text(AppLocalizations.of(context)!
                   .rootPickerSkipConfirmationDialogContent),
               actions: <Widget>[
                 TextButton(
@@ -174,7 +179,7 @@ class _RootPickerState extends State<RootPicker>
     if (roots.isEmpty) {
       SnackBarManager().showSnackBar(SnackBar(
         content:
-            Text(AppLocalizations.of(context).rootPickerListEmptyNotification),
+            Text(AppLocalizations.of(context)!.rootPickerListEmptyNotification),
         duration: k.snackBarDurationNormal,
       ));
       return;
@@ -189,12 +194,12 @@ class _RootPickerState extends State<RootPicker>
       return;
     }
     _isInitDialogShown = true;
-    SchedulerBinding.instance.addPostFrameCallback((_) {
+    SchedulerBinding.instance!.addPostFrameCallback((_) {
       showDialog(
         barrierDismissible: false,
         context: context,
         builder: (context) => ProcessingDialog(
-            text: AppLocalizations.of(context).genericProcessingDialogContent),
+            text: AppLocalizations.of(context)!.genericProcessingDialogContent),
       );
     });
   }

lib/widget/selectable.dart

@@ -5,10 +5,10 @@ import 'package:nc_photos/theme.dart';
 // Overlay a check mark if an item is selected
 class Selectable extends StatelessWidget {
   Selectable({
-    Key key,
+    Key? key,
-    @required this.child,
+    required this.child,
     this.isSelected = false,
-    @required this.iconSize,
+    required this.iconSize,
     this.borderRadius,
     this.onTap,
     this.onLongPress,
@@ -55,8 +55,8 @@ class Selectable extends StatelessWidget {
   final Widget child;
   final bool isSelected;
   final double iconSize;
-  final BorderRadiusGeometry borderRadius;
+  final BorderRadius? borderRadius;
 
-  final VoidCallback onTap;
+  final VoidCallback? onTap;
-  final VoidCallback onLongPress;
+  final VoidCallback? onLongPress;
 }

lib/widget/selectable_item_stream_list_mixin.dart

@@ -18,7 +18,7 @@ import 'package:nc_photos/widget/selectable.dart';
 abstract class SelectableItem {
   Widget buildWidget(BuildContext context);
 
-  VoidCallback get onTap => null;
+  VoidCallback? get onTap => null;
   bool get isSelectable => false;
   StaggeredTile get staggeredTile => const StaggeredTile.count(1, 1);
 }
@@ -33,7 +33,7 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
   @protected
   Widget buildItemStreamListOuter(
     BuildContext context, {
-    @required Widget child,
+    required Widget child,
   }) {
     if (platform_k.isWeb) {
       // support shift+click group selection on web
@@ -51,8 +51,8 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
 
   @protected
   Widget buildItemStreamList({
-    @required double maxCrossAxisExtent,
+    required double maxCrossAxisExtent,
-    ValueChanged<double> onMaxExtentChanged,
+    ValueChanged<double?>? onMaxExtentChanged,
   }) {
     return MeasurableItemList(
       key: _listKey,
@@ -81,24 +81,25 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
   @protected
   set itemStreamListItems(List<SelectableItem> newItems) {
     final lastSelectedItem =
-        _lastSelectPosition != null ? _items[_lastSelectPosition] : null;
+        _lastSelectPosition != null ? _items[_lastSelectPosition!] : null;
 
     _items = newItems;
     _transformSelectedItems();
 
     // Keep _lastSelectPosition if no changes, drop otherwise
-    int newLastSelectPosition;
+    int? newLastSelectPosition;
     try {
       if (lastSelectedItem != null &&
-          lastSelectedItem == _items[_lastSelectPosition]) {
+          lastSelectedItem == _items[_lastSelectPosition!]) {
-        newLastSelectPosition = _lastSelectPosition;
+        newLastSelectPosition = _lastSelectPosition!;
       }
     } catch (_) {}
     _lastSelectPosition = newLastSelectPosition;
 
     _log.info("[itemStreamListItems] updateListHeight: list item changed");
-    WidgetsBinding.instance.addPostFrameCallback((_) =>
+    WidgetsBinding.instance!.addPostFrameCallback((_) =>
-        (_listKey.currentState as MeasurableItemListState)?.updateListHeight());
+        (_listKey.currentState as MeasurableItemListState?)
+            ?.updateListHeight());
   }
 
   Widget _buildItem(BuildContext context, int index) {
@@ -139,8 +140,8 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
         if (_isRangeSelectionMode && _lastSelectPosition != null) {
           setState(() {
             _selectedItems.addAll(_items
-                .sublist(math.min(_lastSelectPosition, index),
+                .sublist(math.min(_lastSelectPosition!, index),
-                    math.max(_lastSelectPosition, index) + 1)
+                    math.max(_lastSelectPosition!, index) + 1)
                 .where((e) => e.isSelectable));
             _lastSelectPosition = index;
           });
@@ -166,8 +167,8 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
     if (!platform_k.isWeb && wasSelectionMode && _lastSelectPosition != null) {
       setState(() {
         _selectedItems.addAll(_items
-            .sublist(math.min(_lastSelectPosition, index),
+            .sublist(math.min(_lastSelectPosition!, index),
-                math.max(_lastSelectPosition, index) + 1)
+                math.max(_lastSelectPosition!, index) + 1)
             .where((e) => e.isSelectable));
         _lastSelectPosition = index;
       });
@@ -183,8 +184,8 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
       if (!SessionStorage().hasShowRangeSelectNotification) {
         SnackBarManager().showSnackBar(SnackBar(
           content: Text(platform_k.isWeb
-              ? AppLocalizations.of(context).webSelectRangeNotification
+              ? AppLocalizations.of(context)!.webSelectRangeNotification
-              : AppLocalizations.of(context).mobileSelectRangeNotification),
+              : AppLocalizations.of(context)!.mobileSelectRangeNotification),
           duration: k.snackBarDurationNormal,
         ));
         SessionStorage().hasShowRangeSelectNotification = true;
@@ -205,14 +206,14 @@ mixin SelectableItemStreamListMixin<T extends StatefulWidget> on State<T> {
             return null;
           }
         })
-        .where((element) => element != null)
+        .whereType<SelectableItem>()
         .toList();
     _selectedItems
       ..clear()
       ..addAll(newSelectedItems);
   }
 
-  int _lastSelectPosition;
+  int? _lastSelectPosition;
   bool _isRangeSelectionMode = false;
 
   var _items = <SelectableItem>[];

lib/widget/settings.dart

@@ -23,12 +23,16 @@ class SettingsArguments {
 class Settings extends StatefulWidget {
   static const routeName = "/settings";
 
+  static Route buildRoute(SettingsArguments args) => MaterialPageRoute(
+        builder: (context) => Settings.fromArgs(args),
+      );
+
   Settings({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
   }) : super(key: key);
 
-  Settings.fromArgs(SettingsArguments args, {Key key})
+  Settings.fromArgs(SettingsArguments args, {Key? key})
       : this(
           account: args.account,
         );
@@ -43,7 +47,7 @@ class _SettingsState extends State<Settings> {
   @override
   initState() {
     super.initState();
-    _isEnableExif = Pref.inst().isEnableExif();
+    _isEnableExif = Pref.inst().isEnableExifOr();
   }
 
   @override
@@ -58,40 +62,41 @@ class _SettingsState extends State<Settings> {
   }
 
   Widget _buildContent(BuildContext context) {
-    final translator = AppLocalizations.of(context).translator;
+    final translator = AppLocalizations.of(context)!.translator;
     return CustomScrollView(
       slivers: [
         SliverAppBar(
           pinned: true,
-          title: Text(AppLocalizations.of(context).settingsWidgetTitle),
+          title: Text(AppLocalizations.of(context)!.settingsWidgetTitle),
         ),
         SliverList(
           delegate: SliverChildListDelegate(
             [
               ListTile(
-                title: Text(AppLocalizations.of(context).settingsLanguageTitle),
+                title:
+                    Text(AppLocalizations.of(context)!.settingsLanguageTitle),
                 subtitle: Text(language_util.getSelectedLanguageName(context)),
                 onTap: () => _onLanguageTap(context),
               ),
               SwitchListTile(
-                title:
+                title: Text(
-                    Text(AppLocalizations.of(context).settingsExifSupportTitle),
+                    AppLocalizations.of(context)!.settingsExifSupportTitle),
                 subtitle: _isEnableExif
-                    ? Text(AppLocalizations.of(context)
+                    ? Text(AppLocalizations.of(context)!
                         .settingsExifSupportTrueSubtitle)
                     : null,
                 value: _isEnableExif,
                 onChanged: (value) => _onExifSupportChanged(context, value),
               ),
               _buildCaption(context,
-                  AppLocalizations.of(context).settingsAboutSectionTitle),
+                  AppLocalizations.of(context)!.settingsAboutSectionTitle),
               ListTile(
-                title: Text(AppLocalizations.of(context).settingsVersionTitle),
+                title: Text(AppLocalizations.of(context)!.settingsVersionTitle),
                 subtitle: const Text(k.versionStr),
               ),
               ListTile(
                 title:
-                    Text(AppLocalizations.of(context).settingsSourceCodeTitle),
+                    Text(AppLocalizations.of(context)!.settingsSourceCodeTitle),
                 subtitle: Text(_sourceRepo),
                 onTap: () async {
                   await launch(_sourceRepo);
@@ -99,7 +104,7 @@ class _SettingsState extends State<Settings> {
               ),
               ListTile(
                 title:
-                    Text(AppLocalizations.of(context).settingsBugReportTitle),
+                    Text(AppLocalizations.of(context)!.settingsBugReportTitle),
                 onTap: () {
                   launch(_bugReportUrl);
                 },
@@ -107,7 +112,7 @@ class _SettingsState extends State<Settings> {
               if (translator.isNotEmpty)
                 ListTile(
                   title: Text(
-                      AppLocalizations.of(context).settingsTranslatorTitle),
+                      AppLocalizations.of(context)!.settingsTranslatorTitle),
                   subtitle: Text(translator),
                   onTap: () {
                     launch(_translationUrl);
@@ -172,8 +177,8 @@ class _SettingsState extends State<Settings> {
         context: context,
         builder: (context) => AlertDialog(
           title: Text(
-              AppLocalizations.of(context).exifSupportConfirmationDialogTitle),
+              AppLocalizations.of(context)!.exifSupportConfirmationDialogTitle),
-          content: Text(AppLocalizations.of(context).exifSupportDetails),
+          content: Text(AppLocalizations.of(context)!.exifSupportDetails),
           actions: <Widget>[
             TextButton(
               onPressed: () {
@@ -185,7 +190,7 @@ class _SettingsState extends State<Settings> {
               onPressed: () {
                 Navigator.of(context).pop(true);
               },
-              child: Text(AppLocalizations.of(context).enableButtonLabel),
+              child: Text(AppLocalizations.of(context)!.enableButtonLabel),
             ),
           ],
         ),
@@ -215,7 +220,7 @@ class _SettingsState extends State<Settings> {
         _log.severe("[_setExifSupport] Failed writing pref");
         SnackBarManager().showSnackBar(SnackBar(
           content: Text(
-              AppLocalizations.of(context).writePreferenceFailureNotification),
+              AppLocalizations.of(context)!.writePreferenceFailureNotification),
           duration: k.snackBarDurationNormal,
         ));
         setState(() {
@@ -231,7 +236,7 @@ class _SettingsState extends State<Settings> {
   static const String _translationUrl =
       "https://gitlab.com/nkming2/nc-photos/-/tree/master/lib/l10n";
 
-  bool _isEnableExif;
+  late bool _isEnableExif;
 
   static final _log = Logger("widget.settings._SettingsState");
 }

lib/widget/setup.dart

@@ -9,7 +9,7 @@ import 'package:nc_photos/widget/sign_in.dart';
 import 'package:page_view_indicators/circle_page_indicator.dart';
 
 bool isNeedSetup() =>
-    Pref.inst().getSetupProgress() & _PageId.all != _PageId.all;
+    Pref.inst().getSetupProgressOr() & _PageId.all != _PageId.all;
 
 class Setup extends StatefulWidget {
   static const routeName = "/setup";
@@ -29,15 +29,15 @@ class _SetupState extends State<Setup> {
     );
   }
 
-  Widget _buildAppBar(BuildContext context) {
+  PreferredSizeWidget _buildAppBar(BuildContext context) {
     return AppBar(
-      title: Text(AppLocalizations.of(context).setupWidgetTitle),
+      title: Text(AppLocalizations.of(context)!.setupWidgetTitle),
       elevation: 0,
     );
   }
 
   Widget _buildContent(BuildContext context) {
-    final page = _pageController.hasClients ? _pageController.page.round() : 0;
+    final page = _pageController.hasClients ? _pageController.page!.round() : 0;
     final pages = <Widget>[
       if (_initialProgress & _PageId.exif == 0) _Exif(),
       if (_initialProgress & _PageId.hiddenPrefDirNotice == 0)
@@ -70,16 +70,21 @@ class _SetupState extends State<Setup> {
                         ElevatedButton(
                           onPressed: _onDonePressed,
                           child: Text(
-                              AppLocalizations.of(context).doneButtonLabel),
+                              AppLocalizations.of(context)!.doneButtonLabel),
                         ),
                       ]
                     : [
                         ElevatedButton(
-                          onPressed: () => _onNextPressed(
+                          onPressed: () {
-                              (pages[_pageController.page.round()] as _Page)
+                            if (_pageController.hasClients) {
-                                  .getPageId()),
+                              _onNextPressed(
+                                  (pages[_pageController.page!.round()]
+                                          as _Page)
+                                      .getPageId());
+                            }
+                          },
                           child: Text(
-                              AppLocalizations.of(context).nextButtonLabel),
+                              AppLocalizations.of(context)!.nextButtonLabel),
                         ),
                       ],
               ),
@@ -107,12 +112,12 @@ class _SetupState extends State<Setup> {
   }
 
   void _onNextPressed(int pageId) {
-    Pref.inst().setSetupProgress(Pref.inst().getSetupProgress() | pageId);
+    Pref.inst().setSetupProgress(Pref.inst().getSetupProgressOr() | pageId);
     _pageController.nextPage(
         duration: k.animationDurationNormal, curve: Curves.easeInOut);
   }
 
-  final _initialProgress = Pref.inst().getSetupProgress();
+  final _initialProgress = Pref.inst().getSetupProgressOr();
   final _pageController = PageController();
   var _currentPageNotifier = ValueNotifier<int>(0);
 }
@@ -143,23 +148,23 @@ class _ExifState extends State<_Exif> {
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
           SwitchListTile(
-            title: Text(AppLocalizations.of(context).settingsExifSupportTitle),
+            title: Text(AppLocalizations.of(context)!.settingsExifSupportTitle),
             value: _isEnableExif,
             onChanged: _onValueChanged,
           ),
           const SizedBox(height: 8),
           Padding(
             padding: const EdgeInsets.symmetric(horizontal: 16),
-            child: Text(AppLocalizations.of(context).exifSupportDetails),
+            child: Text(AppLocalizations.of(context)!.exifSupportDetails),
           ),
           const SizedBox(height: 16),
           Padding(
             padding: const EdgeInsets.symmetric(horizontal: 16),
             child: Text(
-                AppLocalizations.of(context).setupSettingsModifyLaterHint,
+                AppLocalizations.of(context)!.setupSettingsModifyLaterHint,
                 style: Theme.of(context)
                     .textTheme
-                    .bodyText2
+                    .bodyText2!
                     .copyWith(fontStyle: FontStyle.italic)),
           ),
           const SizedBox(height: 8),
@@ -175,7 +180,7 @@ class _ExifState extends State<_Exif> {
     });
   }
 
-  bool _isEnableExif = Pref.inst().isEnableExif();
+  bool _isEnableExif = Pref.inst().isEnableExifOr();
 }
 
 class _HiddenPrefDirNotice extends StatefulWidget implements _Page {
@@ -196,7 +201,7 @@ class _HiddenPrefDirNoticeState extends State<_HiddenPrefDirNotice> {
           Padding(
             padding: const EdgeInsets.symmetric(horizontal: 16),
             child: Text(
-                AppLocalizations.of(context).setupHiddenPrefDirNoticeDetail),
+                AppLocalizations.of(context)!.setupHiddenPrefDirNoticeDetail),
           ),
           const SizedBox(height: 24),
           Align(

lib/widget/sign_in.dart

@@ -16,7 +16,7 @@ import 'package:nc_photos/widget/root_picker.dart';
 class SignIn extends StatefulWidget {
   static const routeName = "/sign-in";
 
-  SignIn({Key key}) : super(key: key);
+  SignIn({Key? key}) : super(key: key);
 
   @override
   createState() => _SignInState();
@@ -49,7 +49,7 @@ class _SignInState extends State<SignIn> {
                       Padding(
                         padding: const EdgeInsets.all(24),
                         child: Text(
-                          AppLocalizations.of(context).signInHeaderText,
+                          AppLocalizations.of(context)!.signInHeaderText,
                           style: Theme.of(context).textTheme.headline5,
                           textAlign: TextAlign.center,
                         ),
@@ -70,7 +70,7 @@ class _SignInState extends State<SignIn> {
                         padding: const EdgeInsets.symmetric(
                             horizontal: 32, vertical: 16),
                         child: Text(
-                          AppLocalizations.of(context).signIn2faHintText,
+                          AppLocalizations.of(context)!.signIn2faHintText,
                           style: TextStyle(fontStyle: FontStyle.italic),
                         ),
                       ),
@@ -82,7 +82,7 @@ class _SignInState extends State<SignIn> {
                         child: Row(
                           mainAxisAlignment: MainAxisAlignment.spaceBetween,
                           children: [
-                            if (!ModalRoute.of(context).isFirst)
+                            if (!ModalRoute.of(context)!.isFirst)
                               TextButton(
                                 onPressed: () {
                                   Navigator.pop(context);
@@ -94,11 +94,11 @@ class _SignInState extends State<SignIn> {
                               Container(),
                             ElevatedButton(
                               onPressed: () {
-                                if (_formKey.currentState.validate()) {
+                                if (_formKey.currentState?.validate() == true) {
                                   _connect();
                                 }
                               },
-                              child: Text(AppLocalizations.of(context)
+                              child: Text(AppLocalizations.of(context)!
                                   .connectButtonLabel),
                             ),
                           ],
@@ -143,11 +143,11 @@ class _SignInState extends State<SignIn> {
                       .toList(),
                   onChanged: (newValue) {
                     setState(() {
-                      _scheme = newValue;
+                      _scheme = newValue!;
                     });
                   },
                   onSaved: (value) {
-                    _formValue.scheme = value.toValueString();
+                    _formValue.scheme = value!.toValueString();
                   },
                 ),
               ),
@@ -159,18 +159,19 @@ class _SignInState extends State<SignIn> {
             Expanded(
               child: TextFormField(
                 decoration: InputDecoration(
-                  hintText: AppLocalizations.of(context).serverAddressInputHint,
+                  hintText:
+                      AppLocalizations.of(context)!.serverAddressInputHint,
                 ),
                 keyboardType: TextInputType.url,
                 validator: (value) {
-                  if (value.trim().trimRightAny("/").isEmpty) {
+                  if (value!.trim().trimRightAny("/").isEmpty) {
-                    return AppLocalizations.of(context)
+                    return AppLocalizations.of(context)!
                         .serverAddressInputInvalidEmpty;
                   }
                   return null;
                 },
                 onSaved: (value) {
-                  _formValue.address = value.trim().trimRightAny("/");
+                  _formValue.address = value!.trim().trimRightAny("/");
                 },
               ),
             ),
@@ -179,32 +180,32 @@ class _SignInState extends State<SignIn> {
         const SizedBox(height: 8),
         TextFormField(
           decoration: InputDecoration(
-            hintText: AppLocalizations.of(context).usernameInputHint,
+            hintText: AppLocalizations.of(context)!.usernameInputHint,
           ),
           validator: (value) {
-            if (value.trim().isEmpty) {
+            if (value!.trim().isEmpty) {
-              return AppLocalizations.of(context).usernameInputInvalidEmpty;
+              return AppLocalizations.of(context)!.usernameInputInvalidEmpty;
             }
             return null;
           },
           onSaved: (value) {
-            _formValue.username = value;
+            _formValue.username = value!;
           },
         ),
         const SizedBox(height: 8),
         TextFormField(
           decoration: InputDecoration(
-            hintText: AppLocalizations.of(context).passwordInputHint,
+            hintText: AppLocalizations.of(context)!.passwordInputHint,
           ),
           obscureText: true,
           validator: (value) {
-            if (value.trim().isEmpty) {
+            if (value!.trim().isEmpty) {
-              return AppLocalizations.of(context).passwordInputInvalidEmpty;
+              return AppLocalizations.of(context)!.passwordInputInvalidEmpty;
             }
             return null;
           },
           onSaved: (value) {
-            _formValue.password = value;
+            _formValue.password = value!;
           },
         ),
       ],
@@ -212,22 +213,23 @@ class _SignInState extends State<SignIn> {
   }
 
   void _connect() {
-    _formKey.currentState.save();
+    _formKey.currentState!.save();
     final account = Account(_formValue.scheme, _formValue.address,
         _formValue.username, _formValue.password, [""]);
     _log.info("[_connect] Try connecting with account: $account");
-    Navigator.pushNamed(context, Connect.routeName,
+    Navigator.pushNamed<Account>(context, Connect.routeName,
             arguments: ConnectArguments(account))
-        .then((result) {
+        .then<Account?>((result) {
       return result != null
           ? Navigator.pushNamed(context, RootPicker.routeName,
               arguments: RootPickerArguments(result))
-          : null;
+          : Future.value(null);
     }).then((result) {
       if (result != null) {
         // we've got a good account
         // only signing in with app password would trigger distinct
-        final accounts = (Pref.inst().getAccounts([])..add(result)).distinct();
+        final accounts =
+            (Pref.inst().getAccountsOr([])..add(result)).distinct();
         Pref.inst()
           ..setAccounts(accounts)
           ..setCurrentAccountIndex(accounts.indexOf(result));
@@ -267,8 +269,8 @@ extension on _Scheme {
 }
 
 class _FormValue {
-  String scheme;
+  late String scheme;
-  String address;
+  late String address;
-  String username;
+  late String username;
-  String password;
+  late String password;
 }

lib/widget/simple_input_dialog.dart

@@ -3,7 +3,7 @@ import 'package:flutter/widgets.dart';
 
 class SimpleInputDialog extends StatefulWidget {
   SimpleInputDialog({
-    Key key,
+    Key? key,
     this.initialText,
     this.hintText,
     this.validator,
@@ -12,9 +12,9 @@ class SimpleInputDialog extends StatefulWidget {
   @override
   createState() => _SimpleInputDialogState();
 
-  final String initialText;
+  final String? initialText;
-  final String hintText;
+  final String? hintText;
-  final FormFieldValidator<String> validator;
+  final FormFieldValidator<String>? validator;
 }
 
 class _SimpleInputDialogState extends State<SimpleInputDialog> {
@@ -29,7 +29,7 @@ class _SimpleInputDialogState extends State<SimpleInputDialog> {
               : InputDecoration(hintText: widget.hintText),
           validator: widget.validator,
           onSaved: (value) {
-            _formValue.text = value;
+            _formValue.text = value!;
           },
           initialValue: widget.initialText,
         ),
@@ -48,15 +48,15 @@ class _SimpleInputDialogState extends State<SimpleInputDialog> {
   void _onSavePressed() {
     if (_formKey.currentState?.validate() == true) {
       _formValue = _FormValue();
-      _formKey.currentState.save();
+      _formKey.currentState!.save();
       Navigator.of(context).pop(_formValue.text);
     }
   }
 
   final _formKey = GlobalKey<FormState>();
-  _FormValue _formValue;
+  var _formValue = _FormValue();
 }
 
 class _FormValue {
-  String text;
+  late String text;
 }

lib/widget/splash.dart

@@ -13,7 +13,7 @@ import 'package:nc_photos/widget/sign_in.dart';
 class Splash extends StatefulWidget {
   static const routeName = "/splash";
 
-  Splash({Key key}) : super(key: key);
+  Splash({Key? key}) : super(key: key);
 
   @override
   createState() => _SplashState();
@@ -23,7 +23,7 @@ class _SplashState extends State<Splash> {
   @override
   initState() {
     super.initState();
-    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
+    WidgetsBinding.instance!.addPostFrameCallback((timeStamp) {
       if (_shouldUpgrade()) {
         _handleUpgrade();
       } else {
@@ -56,7 +56,7 @@ class _SplashState extends State<Splash> {
             ),
             const SizedBox(height: 8),
             Text(
-              AppLocalizations.of(context).appTitle,
+              AppLocalizations.of(context)!.appTitle,
               textAlign: TextAlign.center,
               style: Theme.of(context).textTheme.headline4,
             )
@@ -81,12 +81,12 @@ class _SplashState extends State<Splash> {
   }
 
   bool _shouldUpgrade() {
-    final lastVersion = Pref.inst().getLastVersion(k.version);
+    final lastVersion = Pref.inst().getLastVersionOr(k.version);
     return lastVersion < k.version;
   }
 
   void _handleUpgrade() {
-    final lastVersion = Pref.inst().getLastVersion(k.version);
+    final lastVersion = Pref.inst().getLastVersionOr(k.version);
     // ...
 
     final change = _gatherChangelog(lastVersion);
@@ -94,7 +94,7 @@ class _SplashState extends State<Splash> {
       showDialog(
         context: context,
         builder: (context) => AlertDialog(
-          title: Text(AppLocalizations.of(context).changelogTitle),
+          title: Text(AppLocalizations.of(context)!.changelogTitle),
           content: SingleChildScrollView(
             child: Text(change),
           ),

lib/widget/video_viewer.dart

@@ -12,8 +12,8 @@ import 'package:wakelock/wakelock.dart';
 
 class VideoViewer extends StatefulWidget {
   VideoViewer({
-    @required this.account,
+    required this.account,
-    @required this.file,
+    required this.file,
     this.onLoaded,
     this.onHeightChanged,
     this.onPlay,
@@ -27,10 +27,10 @@ class VideoViewer extends StatefulWidget {
 
   final Account account;
   final File file;
-  final VoidCallback onLoaded;
+  final VoidCallback? onLoaded;
-  final void Function(double height) onHeightChanged;
+  final ValueChanged<double>? onHeightChanged;
-  final VoidCallback onPlay;
+  final VoidCallback? onPlay;
-  final VoidCallback onPause;
+  final VoidCallback? onPause;
   final bool isControlVisible;
   final bool canPlay;
 }
@@ -47,9 +47,9 @@ class _VideoViewerState extends State<VideoViewer> {
     )..initialize().then((_) {
         widget.onLoaded?.call();
         setState(() {});
-        WidgetsBinding.instance.addPostFrameCallback((_) {
+        WidgetsBinding.instance!.addPostFrameCallback((_) {
           if (_key.currentContext != null) {
-            widget.onHeightChanged?.call(_key.currentContext.size.height);
+            widget.onHeightChanged?.call(_key.currentContext!.size!.height);
           }
         });
       }).catchError((e, stacktrace) {
@@ -80,13 +80,13 @@ class _VideoViewerState extends State<VideoViewer> {
   @override
   dispose() {
     super.dispose();
-    _controller?.dispose();
+    _controller.dispose();
     Wakelock.disable();
   }
 
   Widget _buildPlayer(BuildContext context) {
     if (_controller.value.isPlaying && !widget.canPlay) {
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
         _pause();
       });
     }
@@ -197,7 +197,7 @@ class _VideoViewerState extends State<VideoViewer> {
   }
 
   final _key = GlobalKey();
-  VideoPlayerController _controller;
+  late VideoPlayerController _controller;
   var _isFinished = false;
 
   static final _log = Logger("widget.video_viewer._VideoViewerState");

lib/widget/viewer.dart

@@ -38,14 +38,18 @@ class ViewerArguments {
 class Viewer extends StatefulWidget {
   static const routeName = "/viewer";
 
+  static Route buildRoute(ViewerArguments args) => MaterialPageRoute(
+        builder: (context) => Viewer.fromArgs(args),
+      );
+
   Viewer({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.streamFiles,
+    required this.streamFiles,
-    @required this.startIndex,
+    required this.startIndex,
   }) : super(key: key);
 
-  Viewer.fromArgs(ViewerArguments args, {Key key})
+  Viewer.fromArgs(ViewerArguments args, {Key? key})
       : this(
           key: key,
           account: args.account,
@@ -124,7 +128,7 @@ class _ViewerState extends State<Viewer> {
         children: [
           Container(color: Colors.black),
           if (!_pageController.hasClients ||
-              !_pageStates[_pageController.page.round()].hasLoaded)
+              !_pageStates[_pageController.page!.round()]!.hasLoaded)
             Align(
               alignment: Alignment.center,
               child: const CircularProgressIndicator(),
@@ -260,7 +264,7 @@ class _ViewerState extends State<Viewer> {
                   if (!_isDetailPaneActive && _canOpenDetailPane())
                     IconButton(
                       icon: const Icon(Icons.more_vert),
-                      tooltip: AppLocalizations.of(context).detailsTooltip,
+                      tooltip: AppLocalizations.of(context)!.detailsTooltip,
                       onPressed: _onDetailsPressed,
                     ),
                 ],
@@ -307,7 +311,7 @@ class _ViewerState extends State<Viewer> {
                         Icons.share_outlined,
                         color: Colors.white.withOpacity(.87),
                       ),
-                      tooltip: AppLocalizations.of(context).shareTooltip,
+                      tooltip: AppLocalizations.of(context)!.shareTooltip,
                       onPressed: () => _onSharePressed(context),
                     ),
                   ),
@@ -318,7 +322,7 @@ class _ViewerState extends State<Viewer> {
                       Icons.download_outlined,
                       color: Colors.white.withOpacity(.87),
                     ),
-                    tooltip: AppLocalizations.of(context).downloadTooltip,
+                    tooltip: AppLocalizations.of(context)!.downloadTooltip,
                     onPressed: () => _onDownloadPressed(context),
                   ),
                 ),
@@ -329,7 +333,7 @@ class _ViewerState extends State<Viewer> {
                       Icons.delete_outlined,
                       color: Colors.white.withOpacity(.87),
                     ),
-                    tooltip: AppLocalizations.of(context).deleteTooltip,
+                    tooltip: AppLocalizations.of(context)!.deleteTooltip,
                     onPressed: () => _onDeletePressed(context),
                   ),
                 ),
@@ -344,7 +348,7 @@ class _ViewerState extends State<Viewer> {
   Widget _buildPage(BuildContext context, int index) {
     if (_pageStates[index] == null) {
       _onCreateNewPage(context, index);
-    } else if (!_pageStates[index].scrollController.hasClients) {
+    } else if (!_pageStates[index]!.scrollController.hasClients) {
       // the page has been moved out of view and is now coming back
       _log.fine("[_buildPage] Recreating page#$index");
       _onRecreatePageAfterMovedOut(context, index);
@@ -359,7 +363,7 @@ class _ViewerState extends State<Viewer> {
       child: NotificationListener<ScrollNotification>(
         onNotification: (notif) => _onPageContentScrolled(notif, index),
         child: SingleChildScrollView(
-          controller: _pageStates[index].scrollController,
+          controller: _pageStates[index]!.scrollController,
           physics:
               _isDetailPaneActive ? null : const NeverScrollableScrollPhysics(),
           child: Stack(
@@ -409,7 +413,7 @@ class _ViewerState extends State<Viewer> {
       return _buildVideoView(context, index);
     } else {
       _log.shout("[_buildItemView] Unknown file format: ${file.contentType}");
-      _pageStates[index].itemHeight = 0;
+      _pageStates[index]!.itemHeight = 0;
       return Container();
     }
   }
@@ -452,7 +456,7 @@ class _ViewerState extends State<Viewer> {
       return false;
     }
     if (notification is ScrollEndNotification) {
-      final scrollPos = _pageStates[index].scrollController.position;
+      final scrollPos = _pageStates[index]!.scrollController.position;
       if (scrollPos.pixels == 0) {
         setState(() {
           _onDetailPaneClosed();
@@ -463,14 +467,15 @@ class _ViewerState extends State<Viewer> {
           // upward, open the pane to its minimal size
           Future.delayed(Duration.zero, () {
             setState(() {
-              _openDetailPane(_pageController.page.toInt(),
+              _openDetailPane(_pageController.page!.toInt(),
                   shouldAnimate: true);
             });
           });
         } else if (scrollPos.userScrollDirection == ScrollDirection.forward) {
           // downward, close the pane
           Future.delayed(Duration.zero, () {
-            _closeDetailPane(_pageController.page.toInt(), shouldAnimate: true);
+            _closeDetailPane(_pageController.page!.toInt(),
+                shouldAnimate: true);
           });
         }
       }
@@ -481,8 +486,8 @@ class _ViewerState extends State<Viewer> {
   void _onImageLoaded(int index) {
     // currently pageview doesn't pre-load pages, we do it manually
     // don't pre-load if user already navigated away
-    if (_pageController.page.round() == index &&
+    if (_pageController.page!.round() == index &&
-        !_pageStates[index].hasLoaded) {
+        !_pageStates[index]!.hasLoaded) {
       _log.info("[_onImageLoaded] Pre-loading nearby images");
       if (index > 0) {
         final prevFile = widget.streamFiles[index - 1];
@@ -497,16 +502,16 @@ class _ViewerState extends State<Viewer> {
         }
       }
       setState(() {
-        _pageStates[index].hasLoaded = true;
+        _pageStates[index]!.hasLoaded = true;
       });
     }
   }
 
   void _onVideoLoaded(int index) {
-    if (_pageController.page.round() == index &&
+    if (_pageController.page!.round() == index &&
-        !_pageStates[index].hasLoaded) {
+        !_pageStates[index]!.hasLoaded) {
       setState(() {
-        _pageStates[index].hasLoaded = true;
+        _pageStates[index]!.hasLoaded = true;
       });
     }
   }
@@ -534,16 +539,16 @@ class _ViewerState extends State<Viewer> {
   /// Called when the page is being built after previously moved out of view
   void _onRecreatePageAfterMovedOut(BuildContext context, int index) {
     if (_isShowDetailPane && !_isClosingDetailPane) {
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
-        if (_pageStates[index].itemHeight != null) {
+        if (_pageStates[index]!.itemHeight != null) {
           setState(() {
             _openDetailPane(index);
           });
         }
       });
     } else {
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) {
-        _pageStates[index].scrollController.jumpTo(0);
+        _pageStates[index]!.scrollController.jumpTo(0);
       });
     }
   }
@@ -551,26 +556,26 @@ class _ViewerState extends State<Viewer> {
   void _onDetailsPressed() {
     if (!_isDetailPaneActive) {
       setState(() {
-        _openDetailPane(_pageController.page.toInt(), shouldAnimate: true);
+        _openDetailPane(_pageController.page!.toInt(), shouldAnimate: true);
       });
     }
   }
 
   void _onSharePressed(BuildContext context) {
     assert(platform_k.isAndroid);
-    final file = widget.streamFiles[_pageController.page.round()];
+    final file = widget.streamFiles[_pageController.page!.round()];
     ShareHandler().shareFiles(context, widget.account, [file]);
   }
 
   void _onDownloadPressed(BuildContext context) async {
-    final file = widget.streamFiles[_pageController.page.round()];
+    final file = widget.streamFiles[_pageController.page!.round()];
     _log.info("[_onDownloadPressed] Downloading file: ${file.path}");
     var controller = SnackBarManager().showSnackBar(SnackBar(
       content:
-          Text(AppLocalizations.of(context).downloadProcessingNotification),
+          Text(AppLocalizations.of(context)!.downloadProcessingNotification),
       duration: k.snackBarDurationShort,
     ));
-    controller?.closed?.whenComplete(() {
+    controller?.closed.whenComplete(() {
       controller = null;
     });
     dynamic result;
@@ -581,7 +586,7 @@ class _ViewerState extends State<Viewer> {
       _log.warning("[_onDownloadPressed] Permission not granted");
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context)
+        content: Text(AppLocalizations.of(context)!
             .downloadFailureNoPermissionNotification),
         duration: k.snackBarDurationNormal,
       ));
@@ -591,9 +596,9 @@ class _ViewerState extends State<Viewer> {
           "[_onDownloadPressed] Failed while downloadFile", e, stacktrace);
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
-        content:
+        content: Text(
-            Text("${AppLocalizations.of(context).downloadFailureNotification}: "
+            "${AppLocalizations.of(context)!.downloadFailureNotification}: "
-                "${exception_util.toUserString(e, context)}"),
+            "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
       return;
@@ -622,19 +627,19 @@ class _ViewerState extends State<Viewer> {
 
     // fallback
     SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context).downloadSuccessNotification),
+      content: Text(AppLocalizations.of(context)!.downloadSuccessNotification),
       duration: k.snackBarDurationShort,
     ));
   }
 
   void _onDeletePressed(BuildContext context) async {
-    final file = widget.streamFiles[_pageController.page.round()];
+    final file = widget.streamFiles[_pageController.page!.round()];
     _log.info("[_onDeletePressed] Removing file: ${file.path}");
     var controller = SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context).deleteProcessingNotification),
+      content: Text(AppLocalizations.of(context)!.deleteProcessingNotification),
       duration: k.snackBarDurationShort,
     ));
-    controller?.closed?.whenComplete(() {
+    controller?.closed.whenComplete(() {
       controller = null;
     });
     try {
@@ -642,7 +647,7 @@ class _ViewerState extends State<Viewer> {
           AlbumRepo(AlbumCachedDataSource()))(widget.account, file);
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context).deleteSuccessNotification),
+        content: Text(AppLocalizations.of(context)!.deleteSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
       Navigator.of(context).pop();
@@ -655,7 +660,7 @@ class _ViewerState extends State<Viewer> {
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
         content:
-            Text("${AppLocalizations.of(context).deleteFailureNotification}: "
+            Text("${AppLocalizations.of(context)!.deleteFailureNotification}: "
                 "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -666,8 +671,9 @@ class _ViewerState extends State<Viewer> {
     if (_pageStates[index]?.itemHeight == null) {
       return MediaQuery.of(context).size.height;
     } else {
-      return _pageStates[index].itemHeight +
+      return _pageStates[index]!.itemHeight! +
-          (MediaQuery.of(context).size.height - _pageStates[index].itemHeight) /
+          (MediaQuery.of(context).size.height -
+                  _pageStates[index]!.itemHeight!) /
               2 -
           4;
     }
@@ -680,10 +686,10 @@ class _ViewerState extends State<Viewer> {
   }
 
   void _updateItemHeight(int index, double height) {
-    if (_pageStates[index].itemHeight != height) {
+    if (_pageStates[index]!.itemHeight != height) {
       _log.fine("[_updateItemHeight] New height of item#$index: $height");
       setState(() {
-        _pageStates[index].itemHeight = height;
+        _pageStates[index]!.itemHeight = height;
         if (_isDetailPaneActive) {
           _openDetailPane(index);
         }
@@ -709,12 +715,12 @@ class _ViewerState extends State<Viewer> {
     _isShowDetailPane = true;
     _isDetailPaneActive = true;
     if (shouldAnimate) {
-      _pageStates[index].scrollController.animateTo(
+      _pageStates[index]!.scrollController.animateTo(
           _calcDetailPaneOpenedScrollPosition(index),
           duration: k.animationDurationNormal,
           curve: Curves.easeOut);
     } else {
-      _pageStates[index]
+      _pageStates[index]!
           .scrollController
           .jumpTo(_calcDetailPaneOpenedScrollPosition(index));
     }
@@ -723,7 +729,7 @@ class _ViewerState extends State<Viewer> {
   void _closeDetailPane(int index, {bool shouldAnimate = false}) {
     _isClosingDetailPane = true;
     if (shouldAnimate) {
-      _pageStates[index].scrollController.animateTo(0,
+      _pageStates[index]!.scrollController.animateTo(0,
           duration: k.animationDurationNormal, curve: Curves.easeOut);
     }
   }
@@ -739,7 +745,7 @@ class _ViewerState extends State<Viewer> {
         .previousPage(
             duration: k.animationDurationNormal, curve: Curves.easeInOut)
         .whenComplete(
-            () => _updateNavigationState(_pageController.page.round()));
+            () => _updateNavigationState(_pageController.page!.round()));
   }
 
   /// Switch to the next image in the stream
@@ -747,7 +753,7 @@ class _ViewerState extends State<Viewer> {
     _pageController
         .nextPage(duration: k.animationDurationNormal, curve: Curves.easeInOut)
         .whenComplete(
-            () => _updateNavigationState(_pageController.page.round()));
+            () => _updateNavigationState(_pageController.page!.round()));
   }
 
   /// Switch to the image on the "left", what that means depend on the current
@@ -819,7 +825,7 @@ class _ViewerState extends State<Viewer> {
 
   var _isZoomed = false;
 
-  PageController _pageController;
+  late PageController _pageController;
   final _pageStates = <int, _PageState>{};
 
   /// used to gain focus on web for keyboard support
@@ -832,6 +838,6 @@ class _PageState {
   _PageState(this.scrollController);
 
   ScrollController scrollController;
-  double itemHeight;
+  double? itemHeight;
   bool hasLoaded = false;
 }

lib/widget/viewer_detail_pane.dart

@@ -32,9 +32,9 @@ import 'package:tuple/tuple.dart';
 
 class ViewerDetailPane extends StatefulWidget {
   const ViewerDetailPane({
-    Key key,
+    Key? key,
-    @required this.account,
+    required this.account,
-    @required this.file,
+    required this.file,
   }) : super(key: key);
 
   @override
@@ -54,7 +54,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
       _log.info("[initState] Metadata missing in File");
     } else {
       _log.info("[initState] Metadata exists in File");
-      if (widget.file.metadata.exif != null) {
+      if (widget.file.metadata!.exif != null) {
         _initMetadata();
       }
     }
@@ -73,29 +73,29 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
     const space = "    ";
     if (widget.file.metadata?.imageWidth != null &&
         widget.file.metadata?.imageHeight != null) {
-      final pixelCount =
+      final pixelCount = widget.file.metadata!.imageWidth! *
-          widget.file.metadata.imageWidth * widget.file.metadata.imageHeight;
+          widget.file.metadata!.imageHeight!;
       if (pixelCount >= 500000) {
         final mpCount = pixelCount / 1000000.0;
-        sizeSubStr += AppLocalizations.of(context)
+        sizeSubStr += AppLocalizations.of(context)!
             .megapixelCount(mpCount.toStringAsFixed(1));
         sizeSubStr += space;
       }
-      sizeSubStr += _byteSizeToString(widget.file.contentLength);
+      sizeSubStr += _byteSizeToString(widget.file.contentLength ?? 0);
     }
 
     String cameraSubStr = "";
     if (_fNumber != null) {
-      cameraSubStr += "f/${_fNumber.toStringAsFixed(1)}$space";
+      cameraSubStr += "f/${_fNumber!.toStringAsFixed(1)}$space";
     }
     if (_exposureTime != null) {
       cameraSubStr +=
-          AppLocalizations.of(context).secondCountSymbol(_exposureTime);
+          AppLocalizations.of(context)!.secondCountSymbol(_exposureTime!);
       cameraSubStr += space;
     }
     if (_focalLength != null) {
-      cameraSubStr += AppLocalizations.of(context)
+      cameraSubStr += AppLocalizations.of(context)!
-          .millimeterCountSymbol(_focalLength.toStringAsFixedTruncated(2));
+          .millimeterCountSymbol(_focalLength!.toStringAsFixedTruncated(2));
       cameraSubStr += space;
     }
     if (_isoSpeedRatings != null) {
@@ -112,12 +112,12 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
             children: [
               _DetailPaneButton(
                 icon: Icons.playlist_add_outlined,
-                label: AppLocalizations.of(context).addToAlbumTooltip,
+                label: AppLocalizations.of(context)!.addToAlbumTooltip,
                 onPressed: () => _onAddToAlbumPressed(context),
               ),
               _DetailPaneButton(
                 icon: Icons.delete_outline,
-                label: AppLocalizations.of(context).deleteTooltip,
+                label: AppLocalizations.of(context)!.deleteTooltip,
                 onPressed: () => _onDeletePressed(context),
               ),
             ],
@@ -154,7 +154,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
                 color: AppTheme.getSecondaryTextColor(context),
               ),
               title: Text(
-                  "${widget.file.metadata.imageWidth} x ${widget.file.metadata.imageHeight}"),
+                  "${widget.file.metadata!.imageWidth} x ${widget.file.metadata!.imageHeight}"),
               subtitle: Text(sizeSubStr),
             )
           else
@@ -163,7 +163,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
                 Icons.aspect_ratio,
                 color: AppTheme.getSecondaryTextColor(context),
               ),
-              title: Text(_byteSizeToString(widget.file.contentLength)),
+              title: Text(_byteSizeToString(widget.file.contentLength ?? 0)),
             ),
           if (_model != null)
             ListTile(
@@ -171,14 +171,14 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
                 Icons.camera_outlined,
                 color: AppTheme.getSecondaryTextColor(context),
               ),
-              title: Text(_model),
+              title: Text(_model!),
               subtitle: cameraSubStr.isNotEmpty ? Text(cameraSubStr) : null,
             ),
           if (features.isSupportMapView && _gps != null)
             SizedBox(
               height: 256,
               child: platform.Map(
-                center: _gps,
+                center: _gps!,
                 zoom: 16,
                 onTap: _onMapTap,
               ),
@@ -190,35 +190,35 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
 
   /// Convert EXIF data to readable format
   void _initMetadata() {
-    final exif = widget.file.metadata.exif;
+    final exif = widget.file.metadata!.exif!;
     _log.info("[_initMetadata] $exif");
 
     if (exif.make != null && exif.model != null) {
       _model = "${exif.make} ${exif.model}";
     }
     if (exif.fNumber != null) {
-      _fNumber = exif.fNumber.toDouble();
+      _fNumber = exif.fNumber!.toDouble();
     }
     if (exif.exposureTime != null) {
-      if (exif.exposureTime.denominator == 1) {
+      if (exif.exposureTime!.denominator == 1) {
-        _exposureTime = exif.exposureTime.numerator.toString();
+        _exposureTime = exif.exposureTime!.numerator.toString();
       } else {
         _exposureTime = exif.exposureTime.toString();
       }
     }
     if (exif.focalLength != null) {
-      _focalLength = exif.focalLength.toDouble();
+      _focalLength = exif.focalLength!.toDouble();
     }
     if (exif.isoSpeedRatings != null) {
-      _isoSpeedRatings = exif.isoSpeedRatings;
+      _isoSpeedRatings = exif.isoSpeedRatings!;
     }
     if (exif.gpsLatitudeRef != null &&
         exif.gpsLatitude != null &&
         exif.gpsLongitudeRef != null &&
         exif.gpsLongitude != null) {
-      final lat = _gpsDmsToDouble(exif.gpsLatitude) *
+      final lat = _gpsDmsToDouble(exif.gpsLatitude!) *
           (exif.gpsLatitudeRef == "S" ? -1 : 1);
-      final lng = _gpsDmsToDouble(exif.gpsLongitude) *
+      final lng = _gpsDmsToDouble(exif.gpsLongitude!) *
           (exif.gpsLongitudeRef == "W" ? -1 : 1);
       _log.fine("GPS: ($lat, $lng)");
       _gps = Tuple2(lat, lng);
@@ -238,7 +238,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
         _log.info("[_onAddToAlbumPressed] Album picked: ${value.name}");
         _addToAlbum(context, value).then((_) {
           SnackBarManager().showSnackBar(SnackBar(
-            content: Text(AppLocalizations.of(context)
+            content: Text(AppLocalizations.of(context)!
                 .addToAlbumSuccessNotification(value.name)),
             duration: k.snackBarDurationNormal,
           ));
@@ -246,7 +246,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
       } else {
         SnackBarManager().showSnackBar(SnackBar(
           content:
-              Text(AppLocalizations.of(context).addToAlbumFailureNotification),
+              Text(AppLocalizations.of(context)!.addToAlbumFailureNotification),
           duration: k.snackBarDurationNormal,
         ));
       }
@@ -255,7 +255,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
           "[_onAddToAlbumPressed] Failed while showDialog", e, stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            "${AppLocalizations.of(context).addToAlbumFailureNotification}: "
+            "${AppLocalizations.of(context)!.addToAlbumFailureNotification}: "
             "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -265,10 +265,10 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
   void _onDeletePressed(BuildContext context) async {
     _log.info("[_onDeletePressed] Removing file: ${widget.file.path}");
     var controller = SnackBarManager().showSnackBar(SnackBar(
-      content: Text(AppLocalizations.of(context).deleteProcessingNotification),
+      content: Text(AppLocalizations.of(context)!.deleteProcessingNotification),
       duration: k.snackBarDurationShort,
     ));
-    controller?.closed?.whenComplete(() {
+    controller?.closed.whenComplete(() {
       controller = null;
     });
     try {
@@ -276,7 +276,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
           AlbumRepo(AlbumCachedDataSource()))(widget.account, widget.file);
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
-        content: Text(AppLocalizations.of(context).deleteSuccessNotification),
+        content: Text(AppLocalizations.of(context)!.deleteSuccessNotification),
         duration: k.snackBarDurationNormal,
       ));
       Navigator.of(context).pop();
@@ -289,7 +289,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
       controller?.close();
       SnackBarManager().showSnackBar(SnackBar(
         content:
-            Text("${AppLocalizations.of(context).deleteFailureNotification}: "
+            Text("${AppLocalizations.of(context)!.deleteFailureNotification}: "
                 "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -300,7 +300,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
     if (platform_k.isAndroid) {
       final intent = AndroidIntent(
         action: "action_view",
-        data: Uri.encodeFull("geo:${_gps.item1},${_gps.item2}?z=16"),
+        data: Uri.encodeFull("geo:${_gps!.item1},${_gps!.item2}?z=16"),
       );
       intent.launch();
     }
@@ -329,7 +329,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
             stacktrace);
         SnackBarManager().showSnackBar(SnackBar(
           content: Text(
-              AppLocalizations.of(context).updateDateTimeFailureNotification),
+              AppLocalizations.of(context)!.updateDateTimeFailureNotification),
           duration: k.snackBarDurationNormal,
         ));
       }
@@ -362,7 +362,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
         _log.info("[_addToAlbum] File already in album: ${widget.file.path}");
         SnackBarManager().showSnackBar(SnackBar(
           content: Text(
-              "${AppLocalizations.of(context).addToAlbumAlreadyAddedNotification}"),
+              "${AppLocalizations.of(context)!.addToAlbumAlreadyAddedNotification}"),
           duration: k.snackBarDurationNormal,
         ));
         return Future.error(ArgumentError("File already in album"));
@@ -381,7 +381,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
       _log.shout("[_addToAlbum] Failed while updating album", e, stacktrace);
       SnackBarManager().showSnackBar(SnackBar(
         content: Text(
-            "${AppLocalizations.of(context).addToAlbumFailureNotification}: "
+            "${AppLocalizations.of(context)!.addToAlbumFailureNotification}: "
             "${exception_util.toUserString(e, context)}"),
         duration: k.snackBarDurationNormal,
       ));
@@ -389,22 +389,26 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
     }
   }
 
-  DateTime _dateTime;
+  late DateTime _dateTime;
   // EXIF data
-  String _model;
+  String? _model;
-  double _fNumber;
+  double? _fNumber;
-  String _exposureTime;
+  String? _exposureTime;
-  double _focalLength;
+  double? _focalLength;
-  int _isoSpeedRatings;
+  int? _isoSpeedRatings;
-  Tuple2<double, double> _gps;
+  Tuple2<double, double>? _gps;
 
   static final _log =
       Logger("widget.viewer_detail_pane._ViewerDetailPaneState");
 }
 
 class _DetailPaneButton extends StatelessWidget {
-  const _DetailPaneButton({Key key, this.icon, this.label, this.onPressed})
+  const _DetailPaneButton({
-      : super(key: key);
+    Key? key,
+    required this.icon,
+    required this.label,
+    required this.onPressed,
+  }) : super(key: key);
 
   @override
   build(BuildContext context) {
@@ -439,7 +443,7 @@ class _DetailPaneButton extends StatelessWidget {
 
   final IconData icon;
   final String label;
-  final VoidCallback onPressed;
+  final VoidCallback? onPressed;
 }
 
 String _byteSizeToString(int byteSize) {

pubspec.yaml

@@ -18,7 +18,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.22.0+2200
 
 environment:
-  sdk: ">=2.10.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter:

test/entity/album_test.dart

@@ -14,6 +14,7 @@ void main() {
         final json = <String, dynamic>{
           "version": Album.version,
           "lastUpdated": "2020-01-02T03:04:05.678901Z",
+          "name": "",
           "provider": <String, dynamic>{
             "type": "static",
             "content": <String, dynamic>{
@@ -30,7 +31,8 @@ void main() {
           },
         };
         expect(
-            Album.fromJson(json),
+            Album.fromJson(json,
+                upgraderV1: null, upgraderV2: null, upgraderV3: null),
             Album(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               name: "",
@@ -63,7 +65,8 @@ void main() {
           },
         };
         expect(
-            Album.fromJson(json),
+            Album.fromJson(json,
+                upgraderV1: null, upgraderV2: null, upgraderV3: null),
             Album(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               name: "album",
@@ -114,7 +117,8 @@ void main() {
             },
           };
           expect(
-              Album.fromJson(json),
+              Album.fromJson(json,
+                  upgraderV1: null, upgraderV2: null, upgraderV3: null),
               Album(
                 lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
                 name: "",
@@ -161,7 +165,8 @@ void main() {
             },
           };
           expect(
-              Album.fromJson(json),
+              Album.fromJson(json,
+                  upgraderV1: null, upgraderV2: null, upgraderV3: null),
               Album(
                 lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
                 name: "",
@@ -203,7 +208,8 @@ void main() {
           },
         };
         expect(
-            Album.fromJson(json),
+            Album.fromJson(json,
+                upgraderV1: null, upgraderV2: null, upgraderV3: null),
             Album(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               name: "",
@@ -242,7 +248,8 @@ void main() {
           },
         };
         expect(
-            Album.fromJson(json),
+            Album.fromJson(json,
+                upgraderV1: null, upgraderV2: null, upgraderV3: null),
             Album(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               name: "",
@@ -260,6 +267,7 @@ void main() {
         final json = <String, dynamic>{
           "version": Album.version,
           "lastUpdated": "2020-01-02T03:04:05.678901Z",
+          "name": "",
           "provider": <String, dynamic>{
             "type": "static",
             "content": <String, dynamic>{
@@ -279,7 +287,8 @@ void main() {
           },
         };
         expect(
-            Album.fromJson(json),
+            Album.fromJson(json,
+                upgraderV1: null, upgraderV2: null, upgraderV3: null),
             Album(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               name: "",

test/entity/file_test.dart

@@ -109,7 +109,7 @@ void main() {
           "version": Metadata.version,
           "lastUpdated": "2020-01-02T03:04:05.678901Z",
         };
-        expect(Metadata.fromJson(json),
+        expect(Metadata.fromJson(json, upgraderV1: null, upgraderV2: null),
             Metadata(lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901)));
       });
 
@@ -120,7 +120,7 @@ void main() {
           "fileEtag": "8a3e0799b6f0711c23cc2d93950eceb5",
         };
         expect(
-            Metadata.fromJson(json),
+            Metadata.fromJson(json, upgraderV1: null, upgraderV2: null),
             Metadata(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               fileEtag: "8a3e0799b6f0711c23cc2d93950eceb5",
@@ -134,7 +134,7 @@ void main() {
           "imageWidth": 1024,
         };
         expect(
-            Metadata.fromJson(json),
+            Metadata.fromJson(json, upgraderV1: null, upgraderV2: null),
             Metadata(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               imageWidth: 1024,
@@ -148,7 +148,7 @@ void main() {
           "imageHeight": 768,
         };
         expect(
-            Metadata.fromJson(json),
+            Metadata.fromJson(json, upgraderV1: null, upgraderV2: null),
             Metadata(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               imageHeight: 768,
@@ -164,7 +164,7 @@ void main() {
           },
         };
         expect(
-            Metadata.fromJson(json),
+            Metadata.fromJson(json, upgraderV1: null, upgraderV2: null),
             Metadata(
               lastUpdated: DateTime.utc(2020, 1, 2, 3, 4, 5, 678, 901),
               exif: Exif({