chore: optimize rebuild column

frontend/app_flowy/lib/plugins/board/application/board_bloc.dart

@@ -88,12 +88,14 @@ class BoardBloc extends Bloc<BoardEvent, BoardState> {
           didReceiveGridUpdate: (GridPB grid) {
             emit(state.copyWith(grid: Some(grid)));
           },
-          didReceiveRows: (List<RowInfo> rowInfos) {
-            emit(state.copyWith(rowInfos: rowInfos));
-          },
           didReceiveError: (FlowyError error) {
             emit(state.copyWith(noneOrError: some(error)));
           },
+          didReceiveGroups: (List<GroupPB> groups) {
+            emit(state.copyWith(
+              groupIds: groups.map((group) => group.groupId).toList(),
+            ));
+          },
         );
       },
     );
@@ -170,6 +172,7 @@ class BoardBloc extends Bloc<BoardEvent, BoardState> {
 
         boardController.addColumns(columns);
         initializeGroups(groups);
+        add(BoardEvent.didReceiveGroups(groups));
       },
       onDeletedGroup: (groupIds) {
         //
@@ -223,6 +226,8 @@ class BoardEvent with _$BoardEvent {
   const factory BoardEvent.didReceiveGridUpdate(
     GridPB grid,
   ) = _DidReceiveGridUpdate;
+  const factory BoardEvent.didReceiveGroups(List<GroupPB> groups) =
+      _DidReceiveGroups;
 }
 
 @freezed
@@ -230,16 +235,16 @@ class BoardState with _$BoardState {
   const factory BoardState({
     required String gridId,
     required Option<GridPB> grid,
+    required List<String> groupIds,
     required Option<RowPB> editingRow,
-    required List<RowInfo> rowInfos,
     required GridLoadingState loadingState,
     required Option<FlowyError> noneOrError,
   }) = _BoardState;
 
   factory BoardState.initial(String gridId) => BoardState(
-        rowInfos: [],
         grid: none(),
         gridId: gridId,
+        groupIds: [],
         editingRow: none(),
         noneOrError: none(),
         loadingState: const _Loading(),

frontend/app_flowy/lib/plugins/board/presentation/board_page.dart

@@ -32,13 +32,15 @@ class BoardPage extends StatelessWidget {
       create: (context) =>
           BoardBloc(view: view)..add(const BoardEvent.initial()),
       child: BlocBuilder<BoardBloc, BoardState>(
+        buildWhen: (previous, current) =>
+            previous.loadingState != current.loadingState,
         builder: (context, state) {
           return state.loadingState.map(
             loading: (_) =>
                 const Center(child: CircularProgressIndicator.adaptive()),
             finish: (result) {
               return result.successOrFail.fold(
-                (_) => BoardContent(),
+                (_) => const BoardContent(),
                 (err) => FlowyErrorPage(err.toString()),
               );
             },
@@ -49,23 +51,36 @@ class BoardPage extends StatelessWidget {
   }
 }
 
-class BoardContent extends StatelessWidget {
+class BoardContent extends StatefulWidget {
+  const BoardContent({Key? key}) : super(key: key);
+
+  @override
+  State<BoardContent> createState() => _BoardContentState();
+}
+
+class _BoardContentState extends State<BoardContent> {
+  late ScrollController scrollController;
   final config = AFBoardConfig(
     columnBackgroundColor: HexColor.fromHex('#F7F8FC'),
   );
 
-  BoardContent({Key? key}) : super(key: key);
+  @override
+  void initState() {
+    scrollController = ScrollController();
+    super.initState();
+  }
 
   @override
   Widget build(BuildContext context) {
     return BlocBuilder<BoardBloc, BoardState>(
+      buildWhen: (previous, current) => previous.groupIds != current.groupIds,
       builder: (context, state) {
         return Container(
           color: Colors.white,
           child: Padding(
             padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 20),
             child: AFBoard(
-              scrollController: ScrollController(),
+              scrollController: scrollController,
               dataController: context.read<BoardBloc>().boardController,
               headerBuilder: _buildHeader,
               footBuilder: _buildFooter,
@@ -85,6 +100,12 @@ class BoardContent extends StatelessWidget {
     );
   }
 
+  @override
+  void dispose() {
+    scrollController.dispose();
+    super.dispose();
+  }
+
   Widget _buildHeader(
       BuildContext context, AFBoardColumnHeaderData headerData) {
     return AppFlowyColumnHeader(
@@ -159,7 +180,7 @@ class BoardContent extends StatelessWidget {
         );
 
     return AppFlowyColumnItemCard(
-      key: ObjectKey(columnItem),
+      key: ValueKey(columnItem.id),
       margin: config.cardPadding,
       decoration: _makeBoxDecoration(context),
       child: BoardCard(