Add image provider backed by content uri

app/lib/mobile/android/content_uri_image_provider.dart

@@ -0,0 +1,64 @@
+import 'dart:ui' as ui show Codec;
+
+import 'package:equatable/equatable.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/rendering.dart';
+import 'package:nc_photos_plugin/nc_photos_plugin.dart';
+
+class ContentUriImage extends ImageProvider<ContentUriImage>
+    with EquatableMixin {
+  /// Creates an object that decodes a content Uri as an image.
+  const ContentUriImage(
+    this.uri, {
+    this.scale = 1.0,
+  });
+
+  @override
+  obtainKey(ImageConfiguration configuration) {
+    return SynchronousFuture<ContentUriImage>(this);
+  }
+
+  @override
+  load(ContentUriImage key, DecoderCallback decode) {
+    return MultiFrameImageStreamCompleter(
+      codec: _loadAsync(key, decode),
+      scale: key.scale,
+      debugLabel: key.uri,
+      informationCollector: () => <DiagnosticsNode>[
+        ErrorDescription("Content uri: $uri"),
+      ],
+    );
+  }
+
+  Future<ui.Codec> _loadAsync(
+      ContentUriImage key, DecoderCallback decode) async {
+    assert(key == this);
+
+    final bytes = await ContentUri.readUri(uri);
+
+    if (bytes.lengthInBytes == 0) {
+      // The file may become available later.
+      PaintingBinding.instance!.imageCache!.evict(key);
+      throw StateError("$uri is empty and cannot be loaded as an image.");
+    }
+
+    return decode(bytes);
+  }
+
+  @override
+  get props => [
+        uri,
+        scale,
+      ];
+
+  @override
+  toString() => "${objectRuntimeType(this, "ContentUriImage")} {"
+      "uri: $uri, "
+      "scale: $scale, "
+      "}";
+
+  final String uri;
+
+  /// The scale to place in the [ImageInfo] object of the image.
+  final double scale;
+}

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/ContentUriChannelHandler.kt

@@ -0,0 +1,45 @@
+package com.nkming.nc_photos.plugin
+
+import android.content.Context
+import android.net.Uri
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+import java.io.FileNotFoundException
+
+class ContentUriChannelHandler(context: Context) :
+	MethodChannel.MethodCallHandler {
+	companion object {
+		const val METHOD_CHANNEL = "${K.LIB_ID}/content_uri_method"
+
+		private const val TAG = "ContentUriChannelHandler"
+	}
+
+	override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
+		when (call.method) {
+			"readUri" -> {
+				try {
+					readUri(call.argument("uri")!!, result)
+				} catch (e: Throwable) {
+					result.error("systemException", e.toString(), null)
+				}
+			}
+
+			else -> result.notImplemented()
+		}
+	}
+
+	private fun readUri(uri: String, result: MethodChannel.Result) {
+		val uriTyped = Uri.parse(uri)
+		try {
+			val bytes =
+				context.contentResolver.openInputStream(uriTyped)!!.use {
+					it.readBytes()
+				}
+			result.success(bytes)
+		} catch (e: FileNotFoundException) {
+			result.error("fileNotFoundException", e.toString(), null)
+		}
+	}
+
+	private val context = context
+}

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/NcPhotosPlugin.kt

@@ -62,6 +62,14 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware {
 				flutterPluginBinding.applicationContext
 			)
 		)
+
+		contentUriMethodChannel = MethodChannel(
+			flutterPluginBinding.binaryMessenger,
+			ContentUriChannelHandler.METHOD_CHANNEL
+		)
+		contentUriMethodChannel.setMethodCallHandler(
+			ContentUriChannelHandler(flutterPluginBinding.applicationContext)
+		)
 	}
 
 	override fun onDetachedFromEngine(
@@ -74,6 +82,7 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware {
 		nativeEventMethodChannel.setMethodCallHandler(null)
 		mediaStoreMethodChannel.setMethodCallHandler(null)
 		imageProcessorMethodChannel.setMethodCallHandler(null)
+		contentUriMethodChannel.setMethodCallHandler(null)
 	}
 
 	override fun onAttachedToActivity(binding: ActivityPluginBinding) {
@@ -100,6 +109,7 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware {
 	private lateinit var nativeEventMethodChannel: MethodChannel
 	private lateinit var mediaStoreMethodChannel: MethodChannel
 	private lateinit var imageProcessorMethodChannel: MethodChannel
+	private lateinit var contentUriMethodChannel: MethodChannel
 
 	private lateinit var lockChannelHandler: LockChannelHandler
 	private lateinit var mediaStoreChannelHandler: MediaStoreChannelHandler

plugin/lib/nc_photos_plugin.dart

@@ -1,5 +1,6 @@
 library nc_photos_plugin;
 
+export 'src/content_uri.dart';
 export 'src/exception.dart';
 export 'src/image_processor.dart';
 export 'src/lock.dart';

plugin/lib/src/content_uri.dart

@@ -0,0 +1,26 @@
+import 'dart:async';
+import 'dart:typed_data';
+
+import 'package:flutter/services.dart';
+import 'package:nc_photos_plugin/src/exception.dart';
+import 'package:nc_photos_plugin/src/k.dart' as k;
+
+class ContentUri {
+  static Future<Uint8List> readUri(String uri) async {
+    try {
+      return await _methodChannel.invokeMethod("readUri", <String, dynamic>{
+        "uri": uri,
+      });
+    } on PlatformException catch (e) {
+      if (e.code == _exceptionFileNotFound) {
+        throw const FileNotFoundException();
+      } else {
+        rethrow;
+      }
+    }
+  }
+
+  static const _methodChannel = MethodChannel("${k.libId}/content_uri_method");
+
+  static const _exceptionFileNotFound = "fileNotFoundException";
+}

plugin/lib/src/exception.dart

@@ -1,3 +1,18 @@
+class FileNotFoundException implements Exception {
+  const FileNotFoundException([this.message]);
+
+  @override
+  toString() {
+    if (message == null) {
+      return "FileNotFoundException";
+    } else {
+      return "FileNotFoundException: $message";
+    }
+  }
+
+  final dynamic message;
+}
+
 /// Platform permission is not granted by user
 class PermissionException implements Exception {
   const PermissionException([this.message]);