🐛 Fix Wechat Moment preview issue (#111)

* 🐛 Filtered previewing assets in the special WeChat Moment picker type

* 🎨 Move WeChat Moment pick method to multi assets page

Author: AlexV525

example/lib/pages/multi_assets_page.dart

@@ -41,6 +41,19 @@ class _MultiAssetsPageState extends State<MultiAssetsPage>
       PickMethodModel.threeItemsGrid(maxAssetsCount),
       PickMethodModel.customFilterOptions(maxAssetsCount),
       PickMethodModel.prependItem(maxAssetsCount),
+      PickMethodModel(
+        icon: '🎭',
+        name: 'WeChat Moment',
+        description: 'Pick assets like the WeChat Moment pattern.',
+        method: (BuildContext context, List<AssetEntity> assets) {
+          return AssetPicker.pickAssets(
+            context,
+            maxAssets: maxAssetsCount,
+            selectedAssets: assets,
+            specialPickerType: SpecialPickerType.wechatMoment,
+          );
+        },
+      ),
       PickMethodModel.noPreview(maxAssetsCount),
       PickMethodModel(
         icon: '🎚',

example/lib/pages/single_assets_page.dart

@@ -41,19 +41,6 @@ class _SingleAssetPageState extends State<SingleAssetPage>
       PickMethodModel.threeItemsGrid(maxAssetsCount),
       PickMethodModel.customFilterOptions(maxAssetsCount),
       PickMethodModel.prependItem(maxAssetsCount),
-      PickMethodModel(
-        icon: '🎭',
-        name: 'WeChat moment',
-        description: 'Pick assets like the WeChat moment pattern.',
-        method: (BuildContext context, List<AssetEntity> assets) {
-          return AssetPicker.pickAssets(
-            context,
-            maxAssets: maxAssetsCount,
-            selectedAssets: assets,
-            specialPickerType: SpecialPickerType.wechatMoment,
-          );
-        },
-      ),
       PickMethodModel.noPreview(maxAssetsCount),
     ];
   }

lib/src/delegates/asset_picker_builder_delegate.dart

@@ -474,6 +474,11 @@ class DefaultAssetPickerBuilderDelegate
   /// 切换路径时的动画曲线
   Curve get switchingPathCurve => Curves.easeInOut;
 
+  /// Whether the [SpecialPickerType.wechatMoment] is enabled.
+  /// 当前是否为微信朋友圈选择模式
+  bool get isWeChatMoment =>
+      specialPickerType == SpecialPickerType.wechatMoment;
+
   /// Whether the preview of assets is enabled.
   /// 资源的预览是否启用
   bool get isPreviewEnabled => specialPickerType != SpecialPickerType.noPreview;
@@ -650,8 +655,7 @@ class DefaultAssetPickerBuilderDelegate
     return Stack(
       children: <Widget>[
         builder,
-        if (specialPickerType != SpecialPickerType.wechatMoment ||
-            asset.type != AssetType.video)
+        if (!isWeChatMoment || asset.type != AssetType.video)
           selectIndicator(context, asset),
       ],
     );
@@ -1108,13 +1112,21 @@ class DefaultAssetPickerBuilderDelegate
       builder: (_, bool isSelectedNotEmpty, __) => GestureDetector(
         onTap: isSelectedNotEmpty
             ? () async {
+                final List<AssetEntity> _selected;
+                if (isWeChatMoment) {
+                  _selected = provider.selectedAssets
+                      .where((AssetEntity e) => e.type == AssetType.image)
+                      .toList();
+                } else {
+                  _selected = provider.selectedAssets;
+                }
                 final List<AssetEntity>? result =
                     await AssetPickerViewer.pushToViewer(
                   context,
                   currentIndex: 0,
-                  previewAssets: provider.selectedAssets,
+                  previewAssets: _selected,
                   previewThumbSize: previewThumbSize,
-                  selectedAssets: provider.selectedAssets,
+                  selectedAssets: _selected,
                   selectorProvider: provider as DefaultAssetPickerProvider,
                   themeData: theme,
                 );
@@ -1232,22 +1244,41 @@ class DefaultAssetPickerBuilderDelegate
           // When the special type is WeChat Moment, pictures and videos cannot
           // be selected at the same time. Video select should be banned if any
           // pictures are selected.
-          if (specialPickerType == SpecialPickerType.wechatMoment &&
+          if (isWeChatMoment &&
               asset.type == AssetType.video &&
               provider.selectedAssets.isNotEmpty) {
             return;
           }
+          final List<AssetEntity> _current;
+          final List<AssetEntity> _selected;
+          final int _index;
+          if (isWeChatMoment) {
+            if (asset.type == AssetType.video) {
+              _current = <AssetEntity>[asset];
+              _selected = <AssetEntity>[];
+              _index = 0;
+            } else {
+              _current = provider.currentAssets
+                  .where((AssetEntity e) => e.type == AssetType.image)
+                  .toList();
+              _selected = provider.selectedAssets;
+              _index = _current.indexOf(asset);
+            }
+          } else {
+            _current = provider.currentAssets;
+            _selected = provider.selectedAssets;
+            _index = index;
+          }
           final List<AssetEntity>? result =
               await AssetPickerViewer.pushToViewer(
             context,
-            currentIndex: index,
-            previewAssets: provider.currentAssets,
+            currentIndex: _index,
+            previewAssets: _current,
             themeData: theme,
             previewThumbSize: previewThumbSize,
-            selectedAssets: provider.selectedAssets,
+            selectedAssets: _selected,
             selectorProvider: provider as DefaultAssetPickerProvider,
-            specialPickerType:
-                asset.type == AssetType.video ? specialPickerType : null,
+            specialPickerType: specialPickerType,
           );
           if (result != null) {
             Navigator.of(context).pop(result);

lib/src/delegates/asset_picker_viewer_builder_delegate.dart

@@ -248,6 +248,11 @@ class DefaultAssetPickerViewerBuilderDelegate
   /// 详情部件是否显示
   final ValueNotifier<bool> isDisplayingDetail = ValueNotifier<bool>(true);
 
+  /// Whether the [SpecialPickerType.wechatMoment] is enabled.
+  /// 当前是否为微信朋友圈选择模式
+  bool get isWeChatMoment =>
+      specialPickerType == SpecialPickerType.wechatMoment;
+
   @override
   void initStateAndTicker(
     AssetPickerViewerState<AssetEntity, AssetPathEntity> s,
@@ -555,8 +560,7 @@ class DefaultAssetPickerViewerBuilderDelegate
               ),
             const Spacer(),
             if (isAppleOS && provider != null) selectButton(context),
-            if (!isAppleOS && provider != null ||
-                specialPickerType == SpecialPickerType.wechatMoment)
+            if (!isAppleOS && provider != null || isWeChatMoment)
               confirmButton(context),
           ],
         ),
@@ -576,14 +580,13 @@ class DefaultAssetPickerViewerBuilderDelegate
       child: Consumer<AssetPickerViewerProvider<AssetEntity>?>(
         builder: (_, AssetPickerViewerProvider<AssetEntity>? provider, __) {
           assert(
-            specialPickerType == SpecialPickerType.wechatMoment ||
-                provider != null,
+            isWeChatMoment || provider != null,
             'Viewer provider must not be null'
             'when the special type is not WeChat moment.',
           );
           return MaterialButton(
             minWidth: () {
-              if (specialPickerType == SpecialPickerType.wechatMoment) {
+              if (isWeChatMoment) {
                 return 48.0;
               }
               return provider!.isSelectedNotEmpty ? 48.0 : 20.0;
@@ -596,7 +599,7 @@ class DefaultAssetPickerViewerBuilderDelegate
             ),
             child: Text(
               () {
-                if (specialPickerType == SpecialPickerType.wechatMoment) {
+                if (isWeChatMoment) {
                   return Constants.textDelegate.confirm;
                 }
                 if (provider!.isSelectedNotEmpty) {
@@ -614,7 +617,7 @@ class DefaultAssetPickerViewerBuilderDelegate
               ),
             ),
             onPressed: () {
-              if (specialPickerType == SpecialPickerType.wechatMoment) {
+              if (isWeChatMoment) {
                 Navigator.of(context).pop(<AssetEntity>[currentAsset]);
                 return;
               }