Handle download in dart to support customized request

android/app/src/main/kotlin/com/nkming/nc_photos/DownloadChannelHandler.kt

@@ -1,109 +0,0 @@
-package com.nkming.nc_photos
-
-import android.app.Activity
-import android.app.DownloadManager
-import android.content.Context
-import android.net.Uri
-import android.os.Build
-import android.os.Environment
-import io.flutter.plugin.common.MethodCall
-import io.flutter.plugin.common.MethodChannel
-
-/**
- * Download a file
- *
- * Methods:
- * Download a file at @a url. If @a shouldNotify is false, no progress
- * notifications would be shown
- * fun downloadUrl(url: String, headers: Map<String, String>?,
- * 		mimeType: String?, filename: String, shouldNotify: Boolean?): String
- */
-class DownloadChannelHandler(activity: Activity) :
-	MethodChannel.MethodCallHandler {
-	companion object {
-		@JvmStatic
-		val CHANNEL = "com.nkming.nc_photos/download"
-	}
-
-	override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
-		when (call.method) {
-			"downloadUrl" -> {
-				try {
-					downloadUrl(
-						call.argument("url")!!,
-						call.argument("headers"),
-						call.argument("mimeType"),
-						call.argument("filename")!!,
-						call.argument("shouldNotify"),
-						result
-					)
-				} catch (e: Throwable) {
-					result.error("systemException", e.toString(), null)
-				}
-			}
-			"cancel" -> {
-				try {
-					cancel(
-						call.argument("id")!!, result
-					)
-				} catch (e: Throwable) {
-					result.error("systemException", e.toString(), null)
-				}
-			}
-			else -> {
-				result.notImplemented()
-			}
-		}
-	}
-
-	private fun downloadUrl(
-		url: String,
-		headers: Map<String, String>?,
-		mimeType: String?,
-		filename: String,
-		shouldNotify: Boolean?,
-		result: MethodChannel.Result
-	) {
-		if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
-			if (!PermissionHandler.ensureWriteExternalStorage(_activity)) {
-				result.error("permissionError", "Permission not granted", null)
-				return
-			}
-		}
-
-		val uri = Uri.parse(url)
-		val req = DownloadManager.Request(uri).apply {
-			setDestinationInExternalPublicDir(
-				Environment.DIRECTORY_DOWNLOADS, filename
-			)
-			for (h in headers ?: mapOf()) {
-				addRequestHeader(h.key, h.value)
-			}
-			if (mimeType != null) {
-				setMimeType(mimeType)
-			}
-			setVisibleInDownloadsUi(true)
-			setNotificationVisibility(
-				if (shouldNotify == false) DownloadManager.Request.VISIBILITY_HIDDEN
-				else DownloadManager.Request.VISIBILITY_VISIBLE
-			)
-			allowScanningByMediaScanner()
-		}
-
-		val id = _downloadManager.enqueue(req)
-		result.success(id)
-	}
-
-	private fun cancel(
-		id: Long, result: MethodChannel.Result
-	) {
-		val count = _downloadManager.remove(id)
-		result.success(count > 0)
-	}
-
-	private val _activity = activity
-	private val _context get() = _activity
-	private val _downloadManager by lazy {
-		_context.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
-	}
-}

android/app/src/main/kotlin/com/nkming/nc_photos/DownloadEventChannelHandler.kt

@@ -1,99 +1,10 @@
 package com.nkming.nc_photos
 
-import android.app.DownloadManager
 import android.content.BroadcastReceiver
 import android.content.Context
 import android.content.Intent
 import android.content.IntentFilter
-import android.net.Uri
-import androidx.core.content.FileProvider
-import io.flutter.Log
 import io.flutter.plugin.common.EventChannel
-import java.io.File
-
-/**
- * Send DownloadManager ACTION_DOWNLOAD_COMPLETE events to flutter
- */
-class DownloadEventCompleteChannelHandler(context: Context) :
-	BroadcastReceiver(), EventChannel.StreamHandler {
-	companion object {
-		@JvmStatic
-		val CHANNEL =
-			"com.nkming.nc_photos/download_event/action_download_complete"
-	}
-
-	override fun onReceive(context: Context?, intent: Intent?) {
-		if (intent?.action != DownloadManager.ACTION_DOWNLOAD_COMPLETE || !intent.hasExtra(
-				DownloadManager.EXTRA_DOWNLOAD_ID
-			)
-		) {
-			return
-		}
-
-		val downloadId =
-			intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0)
-		// check the status of the job and retrieve the local URI
-		val c = _downloadManager.query(
-			DownloadManager.Query().setFilterById(downloadId)
-		)
-		if (c.moveToFirst()) {
-			val status =
-				c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS))
-			if (status == DownloadManager.STATUS_SUCCESSFUL) {
-				val uri =
-					c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI))
-				val contentUri = FileProvider.getUriForFile(
-					_context,
-					"${BuildConfig.APPLICATION_ID}.fileprovider",
-					File(Uri.parse(uri).path!!)
-				)
-				_eventSink?.success(
-					mapOf(
-						"downloadId" to downloadId,
-						"uri" to contentUri.toString()
-					)
-				)
-			} else if (status == DownloadManager.STATUS_FAILED) {
-				val reason =
-					c.getInt(c.getColumnIndex(DownloadManager.COLUMN_REASON))
-				_eventSink?.error(
-					"downloadError",
-					"Download #$downloadId was not successful, status: $status, reason: $reason",
-					mapOf(
-						"downloadId" to downloadId
-					)
-				)
-			}
-		} else {
-			Log.i(
-				"DownloadEventCompleteChannelHandler.onReceive",
-				"ID #$downloadId not found, user canceled the job?"
-			)
-			_eventSink?.error(
-				"userCanceled", "Download #$downloadId was canceled", mapOf(
-					"downloadId" to downloadId
-				)
-			)
-		}
-	}
-
-	override fun onListen(arguments: Any?, events: EventChannel.EventSink) {
-		_context.registerReceiver(
-			this, IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE)
-		)
-		_eventSink = events
-	}
-
-	override fun onCancel(arguments: Any?) {
-		_context.unregisterReceiver(this)
-	}
-
-	private val _context = context
-	private var _eventSink: EventChannel.EventSink? = null
-	private val _downloadManager by lazy {
-		_context.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
-	}
-}
 
 class DownloadEventCancelChannelHandler(context: Context) : BroadcastReceiver(),
 	EventChannel.StreamHandler {

android/app/src/main/kotlin/com/nkming/nc_photos/MainActivity.kt

@@ -9,9 +9,6 @@ import io.flutter.plugin.common.MethodChannel
 class MainActivity : FlutterActivity() {
 	override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
 		super.configureFlutterEngine(flutterEngine)
-		MethodChannel(flutterEngine.dartExecutor.binaryMessenger,
-				DownloadChannelHandler.CHANNEL).setMethodCallHandler(
-				DownloadChannelHandler(this))
 		MethodChannel(flutterEngine.dartExecutor.binaryMessenger,
 				MediaStoreChannelHandler.CHANNEL).setMethodCallHandler(
 				MediaStoreChannelHandler(this))
@@ -25,9 +22,6 @@ class MainActivity : FlutterActivity() {
 				ShareChannelHandler.CHANNEL).setMethodCallHandler(
 				ShareChannelHandler(this))
 
-		EventChannel(flutterEngine.dartExecutor.binaryMessenger,
-				DownloadEventCompleteChannelHandler.CHANNEL).setStreamHandler(
-				DownloadEventCompleteChannelHandler(this))
 		EventChannel(flutterEngine.dartExecutor.binaryMessenger,
 				DownloadEventCancelChannelHandler.CHANNEL).setStreamHandler(
 				DownloadEventCancelChannelHandler(this))

android/app/src/main/kotlin/com/nkming/nc_photos/MediaStoreChannelHandler.kt

@@ -11,9 +11,7 @@ import androidx.annotation.RequiresApi
 import androidx.core.content.FileProvider
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
-import java.io.BufferedOutputStream
+import java.io.*
-import java.io.File
-import java.io.FileOutputStream
 
 /*
  * Save downloaded item on device
@@ -31,8 +29,8 @@ class MediaStoreChannelHandler(activity: Activity) :
 	}
 
 	override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
-		if (call.method == "saveFileToDownload") {
+		when (call.method) {
-			try {
+			"saveFileToDownload" -> try {
 				saveFileToDownload(
 					call.argument("fileName")!!,
 					call.argument("content")!!,
@@ -41,24 +39,47 @@ class MediaStoreChannelHandler(activity: Activity) :
 			} catch (e: Throwable) {
 				result.error("systemException", e.message, null)
 			}
-		} else {
+			"copyFileToDownload" -> try {
-			result.notImplemented()
+				copyFileToDownload(
+					call.argument("toFileName")!!,
+					call.argument("fromFilePath")!!,
+					result
+				)
+			} catch (e: Throwable) {
+				result.error("systemException", e.message, null)
+			}
+			else -> result.notImplemented()
 		}
 	}
 
 	private fun saveFileToDownload(
 		fileName: String, content: ByteArray, result: MethodChannel.Result
+	) {
+		val stream = ByteArrayInputStream(content)
+		writeFileToDownload(fileName, stream, result)
+	}
+
+	private fun copyFileToDownload(
+		toFileName: String, fromFilePath: String, result: MethodChannel.Result
+	) {
+		val file = File(fromFilePath)
+		val stream = file.inputStream()
+		writeFileToDownload(toFileName, stream, result)
+	}
+
+	private fun writeFileToDownload(
+		fileName: String, data: InputStream, result: MethodChannel.Result
 	) {
 		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-			saveFileToDownload29(fileName, content, result)
+			writeFileToDownload29(fileName, data, result)
 		} else {
-			saveFileToDownload0(fileName, content, result)
+			writeFileToDownload0(fileName, data, result)
 		}
 	}
 
 	@RequiresApi(Build.VERSION_CODES.Q)
-	private fun saveFileToDownload29(
+	private fun writeFileToDownload29(
-		fileName: String, content: ByteArray, result: MethodChannel.Result
+		fileName: String, data: InputStream, result: MethodChannel.Result
 	) {
 		// Add a media item that other apps shouldn't see until the item is
 		// fully written to the media store.
@@ -77,14 +98,14 @@ class MediaStoreChannelHandler(activity: Activity) :
 		resolver.openFileDescriptor(contentUri!!, "w", null).use { pfd ->
 			// Write data into the pending audio file.
 			BufferedOutputStream(FileOutputStream(pfd!!.fileDescriptor)).use { stream ->
-				stream.write(content)
+				data.copyTo(stream)
 			}
 		}
 		result.success(contentUri.toString())
 	}
 
-	private fun saveFileToDownload0(
+	private fun writeFileToDownload0(
-		fileName: String, content: ByteArray, result: MethodChannel.Result
+		fileName: String, data: InputStream, result: MethodChannel.Result
 	) {
 		if (!PermissionHandler.ensureWriteExternalStorage(_activity)) {
 			result.error("permissionError", "Permission not granted", null)
@@ -103,7 +124,7 @@ class MediaStoreChannelHandler(activity: Activity) :
 			++count
 		}
 		BufferedOutputStream(FileOutputStream(file)).use { stream ->
-			stream.write(content)
+			data.copyTo(stream)
 		}
 
 		val fileUri = Uri.fromFile(file)

lib/mobile/android/download.dart

@@ -2,66 +2,13 @@ import 'dart:async';
 
 import 'package:flutter/services.dart';
 
-class Download {
-  static Future<int> downloadUrl({
-    required String url,
-    Map<String, String>? headers,
-    String? mimeType,
-    required String filename,
-    bool? shouldNotify,
-  }) async {
-    return (await _channel.invokeMethod<int>("downloadUrl", <String, dynamic>{
-      "url": url,
-      "headers": headers,
-      "mimeType": mimeType,
-      "filename": filename,
-      "shouldNotify": shouldNotify,
-    }))!;
-  }
-
-  static Future<bool> cancel({
-    required int id,
-  }) async {
-    return (await _channel.invokeMethod<bool>("cancel", <String, dynamic>{
-      "id": id,
-    }))!;
-  }
-
-  /// The download job has failed
-  static const exceptionCodeDownloadError = "downloadError";
-
-  static const _channel = MethodChannel("com.nkming.nc_photos/download");
-}
-
 class DownloadEvent {
-  static StreamSubscription<DownloadCompleteEvent> listenDownloadComplete() =>
-      _completeStream.listen(null);
-
   static StreamSubscription<DownloadCancelEvent> listenDownloadCancel() =>
       _cancelStream.listen(null);
 
   /// User canceled the download job
   static const exceptionCodeUserCanceled = "userCanceled";
 
-  static const _downloadCompleteChannel = EventChannel(
-      "com.nkming.nc_photos/download_event/action_download_complete");
-
-  static late final _completeStream = _downloadCompleteChannel
-      .receiveBroadcastStream()
-      .map((data) => DownloadCompleteEvent(
-            data["downloadId"],
-            data["uri"],
-          ))
-      .handleError(
-    (e, stackTrace) {
-      throw AndroidDownloadError(e.details["downloadId"], e, stackTrace);
-    },
-    test: (e) =>
-        e is PlatformException &&
-        e.details is Map &&
-        e.details["downloadId"] is int,
-  );
-
   static const _downloadCancelChannel = EventChannel(
       "com.nkming.nc_photos/download_event/action_download_cancel");
 
@@ -72,21 +19,6 @@ class DownloadEvent {
           ));
 }
 
-class DownloadCompleteEvent {
-  const DownloadCompleteEvent(this.downloadId, this.uri);
-
-  final int downloadId;
-  final String uri;
-}
-
-class AndroidDownloadError implements Exception {
-  const AndroidDownloadError(this.downloadId, this.error, this.stackTrace);
-
-  final int downloadId;
-  final dynamic error;
-  final StackTrace stackTrace;
-}
-
 class DownloadCancelEvent {
   const DownloadCancelEvent(this.notificationId);
 

lib/mobile/android/media_store.dart

@@ -14,5 +14,14 @@ class MediaStore {
     }))!;
   }
 
+  static Future<String> copyFileToDownload(
+      String toFileName, String fromFilePath) async {
+    return (await _channel
+        .invokeMethod<String>("copyFileToDownload", <String, dynamic>{
+      "toFileName": toFileName,
+      "fromFilePath": fromFilePath,
+    }))!;
+  }
+
   static const _channel = MethodChannel("com.nkming.nc_photos/media_store");
 }

lib/mobile/download.dart

@@ -1,12 +1,14 @@
 import 'dart:async';
+import 'dart:io';
 
-import 'package:flutter/services.dart';
+import 'package:http/http.dart' as http;
 import 'package:logging/logging.dart';
 import 'package:nc_photos/exception.dart';
-import 'package:nc_photos/mobile/android/download.dart' as android;
 import 'package:nc_photos/mobile/android/media_store.dart';
 import 'package:nc_photos/platform/download.dart' as itf;
 import 'package:nc_photos/platform/k.dart' as platform_k;
+import 'package:path_provider/path_provider.dart';
+import 'package:uuid/uuid.dart';
 
 class DownloadBuilder extends itf.DownloadBuilder {
   @override
@@ -45,77 +47,99 @@ class _AndroidDownload extends itf.Download {
 
   @override
   call() async {
-    final String path;
+    if (_isInitialDownload) {
-    if (parentDir?.isNotEmpty == true) {
+      await _cleanUp();
-      path = "$parentDir/$filename";
+      _isInitialDownload = false;
-    } else {
-      path = filename;
     }
-
+    final file = await _createTempFile();
     try {
-      _log.info("[call] Start downloading '$url'");
+      // download file to a temp dir
-      _downloadId = await android.Download.downloadUrl(
+      final fileWrite = file.openWrite();
-        url: url,
-        headers: headers,
-        mimeType: mimeType,
-        filename: path,
-        shouldNotify: shouldNotify,
-      );
-      _log.info("[call] #$_downloadId -> '$url'");
-      late final String uri;
-      final completer = Completer();
-      onDownloadComplete(android.DownloadCompleteEvent ev) {
-        if (ev.downloadId == _downloadId) {
-          _log.info("[call] Finished downloading '$url' to '${ev.uri}'");
-          uri = ev.uri;
-          completer.complete();
-        }
-      }
-
-      StreamSubscription<android.DownloadCompleteEvent>? subscription;
       try {
-        subscription = android.DownloadEvent.listenDownloadComplete()
+        final uri = Uri.parse(url);
-          ..onData(onDownloadComplete)
+        final req = http.Request("GET", uri)..headers.addAll(headers ?? {});
-          ..onError((e, stackTrace) {
+        final response = await http.Client().send(req);
-            if (e is android.AndroidDownloadError) {
+        bool isEnd = false;
-              if (e.downloadId != _downloadId) {
+        Object? error;
-                // not us, ignore
+        final subscription = response.stream.listen(
-                return;
+          fileWrite.add,
-              }
+          onDone: () {
-              completer.completeError(e.error, e.stackTrace);
+            isEnd = true;
-            } else {
+          },
-              completer.completeError(e, stackTrace);
+          onError: (e, stackTrace) {
-            }
+            _log.severe("Failed while request", e, stackTrace);
-          });
+            isEnd = true;
-        await completer.future;
+            error = e;
+          },
+          cancelOnError: true,
+        );
+        // wait until download finished
+        while (!isEnd) {
+          if (shouldInterrupt) {
+            await subscription.cancel();
+            break;
+          }
+          await Future.delayed(const Duration(seconds: 1));
+        }
+        if (error != null) {
+          throw error!;
+        }
       } finally {
-        subscription?.cancel();
+        fileWrite.close();
       }
-      return uri;
+      if (shouldInterrupt) {
-    } on PlatformException catch (e) {
+        throw JobCanceledException();
-      switch (e.code) {
-        case MediaStore.exceptionCodePermissionError:
-          throw PermissionException();
-
-        case android.Download.exceptionCodeDownloadError:
-          throw DownloadException(e.message);
-
-        case android.DownloadEvent.exceptionCodeUserCanceled:
-          throw JobCanceledException(e.message);
-
-        default:
-          rethrow;
       }
+
+      // copy the file to the actual dir
+      final String path;
+      if (parentDir?.isNotEmpty == true) {
+        path = "$parentDir/$filename";
+      } else {
+        path = filename;
+      }
+      return await MediaStore.copyFileToDownload(path, file.path);
+    } finally {
+      file.delete();
     }
   }
 
   @override
-  cancel() async {
+  cancel() {
-    if (_downloadId != null) {
+    shouldInterrupt = true;
-      _log.info("[cancel] Cancel #$_downloadId");
+    return true;
-      return await android.Download.cancel(id: _downloadId!);
+  }
+
+  Future<Directory> _openDownloadDir() async {
+    final tempDir = await getTemporaryDirectory();
+    final downloadDir = Directory("${tempDir.path}/downloads");
+    if (!await downloadDir.exists()) {
+      return downloadDir.create();
     } else {
-      return false;
+      return downloadDir;
+    }
+  }
+
+  Future<File> _createTempFile() async {
+    final downloadDir = await _openDownloadDir();
+    while (true) {
+      final fileName = const Uuid().v4();
+      final file = File("${downloadDir.path}/$fileName");
+      if (await file.exists()) {
+        continue;
+      }
+      return file;
+    }
+  }
+
+  /// Clean up remaining cache files from previous runs
+  ///
+  /// Normally the files will be deleted automatically
+  Future<void> _cleanUp() async {
+    final downloadDir = await _openDownloadDir();
+    await for (final f in downloadDir.list(followLinks: false)) {
+      _log.warning("[_cleanUp] Deleting file: ${f.path}");
+      await f.delete();
     }
   }
 
@@ -125,7 +149,10 @@ class _AndroidDownload extends itf.Download {
   final String filename;
   final String? parentDir;
   final bool? shouldNotify;
-  int? _downloadId;
+
+  bool shouldInterrupt = false;
+
+  static bool _isInitialDownload = true;
 
   static final _log = Logger("mobile.download._AndroidDownload");
 }

lib/platform/download.dart

@@ -8,8 +8,11 @@ abstract class Download {
 
   /// Cancel a download
   ///
-  /// Not all platforms support canceling an ongoing download
+  /// Not all platforms support canceling an ongoing download. Return true if
-  Future<bool> cancel();
+  /// the current platform supports it, however there's no guarantee if and when
+  /// the download task would be canceled. After a download is canceled
+  /// successfully, [JobCanceledException] will be thrown in [call]
+  bool cancel();
 }
 
 abstract class DownloadBuilder {

lib/web/download.dart

@@ -43,7 +43,7 @@ class _WebDownload extends itf.Download {
   }
 
   @override
-  cancel() => Future.value(false);
+  cancel() => false;
 
   final String url;
   final Map<String, String>? headers;