✨ Add previewThumbSize for the viewer.

Author: AlexV525

lib/src/provider/asset_entity_image_provider.dart

@@ -11,12 +11,21 @@ import 'package:photo_manager/photo_manager.dart';
 
 @immutable
 class AssetEntityImageProvider extends ImageProvider<AssetEntityImageProvider> {
-  const AssetEntityImageProvider(
+  AssetEntityImageProvider(
     this.entity, {
     this.scale = 1.0,
-    this.thumbSize = 200,
+    this.thumbSize = const <int>[200, 200],
     this.isOriginal = true,
-  });
+  }) : assert(
+          thumbSize?.length == 2,
+          'thumbSize must contain and only contain two integers',
+        ) {
+    if (thumbSize?.length != 2) {
+      throw ArgumentError(
+        'thumbSize must contain and only contain two integers',
+      );
+    }
+  }
 
   final AssetEntity entity;
 
@@ -26,7 +35,7 @@ class AssetEntityImageProvider extends ImageProvider<AssetEntityImageProvider> {
 
   /// Size for thumb data.
   /// 缩略图的大小
-  final int thumbSize;
+  final List<int> thumbSize;
 
   /// Choose if original data or thumb data should be loaded.
   /// 选择载入原数据还是缩略图数据
@@ -71,7 +80,7 @@ class AssetEntityImageProvider extends ImageProvider<AssetEntityImageProvider> {
         data = await key.entity.originBytes;
       }
     } else {
-      data = await key.entity.thumbDataWithSize(thumbSize, thumbSize);
+      data = await key.entity.thumbDataWithSize(thumbSize[0], thumbSize[1]);
     }
     return decode(data);
   }

lib/src/widget/asset_picker.dart

@@ -24,10 +24,11 @@ class AssetPicker extends StatelessWidget {
   AssetPicker({
     Key key,
     @required this.provider,
-    this.pickerTheme,
     int gridCount = 4,
     Color themeColor,
     AssetsPickerTextDelegate textDelegate,
+    this.pickerTheme,
+    this.previewThumbSize,
     this.specialPickerType,
     this.customItemPosition = CustomItemPosition.none,
     this.customItemBuilder,
@@ -61,11 +62,25 @@ class AssetPicker extends StatelessWidget {
   /// Theme for the picker.
   /// 选择器的主题
   ///
-  /// Usually the WeChat uses the dark version (dark background color) for the picker.
-  /// However, some developer wants a light theme version for some reasons.
+  /// Usually the WeChat uses the dark version (dark background color)
+  /// for the picker. However, some others want a light or a custom version.
+  ///
   /// 通常情况下微信选择器使用的是暗色（暗色背景）的主题，但某些情况下开发者需要亮色或自定义主题。
   final ThemeData pickerTheme;
 
+  /// Thumb size for the preview of images in the viewer.
+  /// 预览时图片的缩略图大小
+  ///
+  /// This only works on images since other types does not have request
+  /// for thumb data. The speed of preview can be raised by reducing it.
+  ///
+  /// 该参数仅生效于图片类型的资源，因为其他资源不需要请求缩略图数据。
+  /// 预览图片的速度可以通过适当降低它的数值来提升。
+  ///
+  /// Default is `null`, which will request the origin data.
+  /// 默认为空，即读取原图。
+  final List<int> previewThumbSize;
+
   /// The current special picker type for the picker.
   /// 当前特殊选择类型
   ///
@@ -93,6 +108,7 @@ class AssetPicker extends StatelessWidget {
     int pageSize = 320,
     int pathThumbSize = 200,
     int gridCount = 4,
+    List<int> previewThumbSize,
     RequestType requestType,
     SpecialPickerType specialPickerType,
     List<AssetEntity> selectedAssets,
@@ -159,6 +175,7 @@ class AssetPicker extends StatelessWidget {
           textDelegate: textDelegate,
           themeColor: themeColor,
           pickerTheme: pickerTheme,
+          previewThumbSize: previewThumbSize,
           specialPickerType: specialPickerType,
           customItemPosition: customItemPosition,
           customItemBuilder: customItemBuilder,
@@ -383,6 +400,7 @@ class AssetPicker extends StatelessWidget {
                       /// The reason that the `thumbData` should be checked at here to see if it is
                       /// null is that even the image file is not exist, the `File` can still
                       /// returned as it exist, which will cause the thumb bytes return null.
+                      ///
                       /// 此处需要检查缩略图为空的原因是：尽管文件可能已经被删除，但通过`File`读取的文件对象
                       /// 仍然存在，使得返回的数据为空。
                       final Uint8List thumbData = pathEntityList[pathEntity];
@@ -587,6 +605,7 @@ class AssetPicker extends StatelessWidget {
   /// 确认按钮
   ///
   /// It'll pop with [AssetPickerProvider.selectedAssets] when there're any assets chosen.
+  ///
   /// 当有资源已选时，点击按钮将把已选资源通过路由返回。
   Widget confirmButton(BuildContext context) => Consumer<AssetPickerProvider>(
         builder: (BuildContext _, AssetPickerProvider provider, Widget __) {
@@ -702,6 +721,7 @@ class AssetPicker extends StatelessWidget {
   /// Videos often contains various of color in the cover,
   /// so in order to keep the content visible in most cases,
   /// the color of the indicator has been set to [Colors.white].
+  ///
   /// 视频封面通常包含各种颜色，为了保证内容在一般情况下可见，此处
   /// 将指示器的图标和文字设置为 [Colors.white]。
   Widget videoIndicator(AssetEntity asset) {
@@ -769,6 +789,7 @@ class AssetPicker extends StatelessWidget {
                 currentIndex: index,
                 assets: provider.currentAssets,
                 themeData: theme,
+                previewThumbSize: previewThumbSize,
                 specialPickerType:
                     asset.type == AssetType.video ? specialPickerType : null,
               );
@@ -1129,6 +1150,7 @@ class AssetPicker extends StatelessWidget {
                     context,
                     currentIndex: 0,
                     assets: provider.selectedAssets,
+                    previewThumbSize: previewThumbSize,
                     selectedAssets: provider.selectedAssets,
                     selectorProvider: provider,
                     themeData: theme,

lib/src/widget/asset_picker_viewer.dart

@@ -28,6 +28,7 @@ class AssetPickerViewer extends StatefulWidget {
     @required this.currentIndex,
     @required this.assets,
     @required this.themeData,
+    this.previewThumbSize,
     this.selectedAssets,
     this.selectorProvider,
     this.specialPickerType,
@@ -53,6 +54,10 @@ class AssetPickerViewer extends StatefulWidget {
   /// 主题
   final ThemeData themeData;
 
+  /// Thumb size for the preview of images in the viewer.
+  /// 预览时图片的缩略图大小
+  final List<int> previewThumbSize;
+
   /// The current special picker type for the viewer.
   /// 当前特殊选择类型
   ///
@@ -70,6 +75,7 @@ class AssetPickerViewer extends StatefulWidget {
     int currentIndex = 0,
     @required List<AssetEntity> assets,
     @required ThemeData themeData,
+    List<int> previewThumbSize,
     List<AssetEntity> selectedAssets,
     AssetPickerProvider selectorProvider,
     SpecialPickerType specialPickerType,
@@ -79,6 +85,7 @@ class AssetPickerViewer extends StatefulWidget {
         currentIndex: currentIndex,
         assets: assets,
         themeData: themeData,
+        previewThumbSize: previewThumbSize,
         selectedAssets: selectedAssets,
         selectorProvider: selectorProvider,
         specialPickerType: specialPickerType,
@@ -247,7 +254,11 @@ class AssetPickerViewerState extends State<AssetPickerViewer>
         builder = AudioPageBuilder(asset: asset, state: this);
         break;
       case AssetType.image:
-        builder = ImagePageBuilder(asset: asset, state: this);
+        builder = ImagePageBuilder(
+          asset: asset,
+          state: this,
+          previewThumbSize: widget.previewThumbSize,
+        );
         break;
       case AssetType.video:
         builder = VideoPageBuilder(asset: asset, state: this);

lib/src/widget/builder/image_page_builder.dart

@@ -11,6 +11,7 @@ class ImagePageBuilder extends StatelessWidget {
     Key key,
     this.asset,
     this.state,
+    this.previewThumbSize,
   }) : super(key: key);
 
   /// Asset currently displayed.
@@ -21,13 +22,19 @@ class ImagePageBuilder extends StatelessWidget {
   /// 资源查看器的状态[State]
   final AssetPickerViewerState state;
 
+  final List<int> previewThumbSize;
+
   @override
   Widget build(BuildContext context) {
     return GestureDetector(
       behavior: HitTestBehavior.opaque,
       onTap: state.switchDisplayingDetail,
       child: ExtendedImage(
-        image: AssetEntityImageProvider(asset),
+        image: AssetEntityImageProvider(
+          asset,
+          isOriginal: previewThumbSize == null,
+          thumbSize: previewThumbSize,
+        ),
         fit: BoxFit.contain,
         mode: ExtendedImageMode.gesture,
         onDoubleTap: state.updateAnimation,