🚑️ Fix not synced issue when the picker is under single pick mode

Author: AlexV525

lib/src/delegates/asset_picker_builder_delegate.dart

@@ -1139,9 +1139,9 @@ class DefaultAssetPickerBuilderDelegate
 
   @override
   Widget selectIndicator(BuildContext context, AssetEntity asset) {
-    return Selector<DefaultAssetPickerProvider, int>(
-      selector: (_, DefaultAssetPickerProvider p) => p.selectedAssetsCount,
-      builder: (BuildContext context, int count, __) {
+    return Selector<DefaultAssetPickerProvider, String>(
+      selector: (_, DefaultAssetPickerProvider p) => p.selectedDescriptions,
+      builder: (BuildContext context, _, __) {
         final List<AssetEntity> selectedAssets =
             context.select<DefaultAssetPickerProvider, List<AssetEntity>>(
           (DefaultAssetPickerProvider p) => p.selectedAssets,

lib/src/provider/asset_picker_provider.dart

@@ -178,13 +178,16 @@ abstract class AssetPickerProvider<A, P> extends ChangeNotifier {
     notifyListeners();
   }
 
-  /// How many assets have been selected.
-  /// 当前有资源已经被选择
+  /// Descriptions for selected assets currently.
+  /// 当前已被选中的资源的描述
   ///
   /// This getter provides a "Should Rebuild" condition judgement to [Selector]
   /// with the preview widget's selective part.
   /// 它为预览部件的选中部分的 [Selector] 提供了是否重建的条件。
-  int get selectedAssetsCount => _selectedAssets.length;
+  String get selectedDescriptions => _selectedAssets.fold(
+        <String>[],
+        (List<String> list, A a) => list..add(a.toString()),
+      ).join();
 
   /// 选中资源是否为空
   bool get isSelectedNotEmpty => selectedAssets.isNotEmpty;