fix(home): 修复频道快速切换卡 loading

lib/core/data/services/home_feed_controller.dart

@@ -10,28 +10,31 @@ import '../../../pages/home/home_feed_channel.dart';
 
 /// 首页内容类型频道状态：每频道独立缓存、刷新和游标分页。
 class HomeFeedController extends ChangeNotifier {
-  HomeFeedController(this._repository)
-    : _states = {
-        for (final channel in HomeFeedChannel.values)
-          channel: _ChannelFeedState(),
-      };
+  HomeFeedController(
+    this._repository, {
+    this.requestTimeout = defaultRequestTimeout,
+  }) : _states = {
+         for (final channel in HomeFeedChannel.values)
+           channel: _ChannelFeedState(),
+       };
 
   static const int pageSize = 10;
+  static const Duration defaultRequestTimeout = Duration(seconds: 10);
 
   final CatalogRepository _repository;
+  final Duration requestTimeout;
   final Map<HomeFeedChannel, _ChannelFeedState> _states;
   HomeFeedChannel _channel = HomeFeedChannel.recommend;
-  String? _lastError;
   bool _disposed = false;
 
   HomeFeedChannel get channel => _channel;
-  String? get lastError => _lastError;
+  String? get lastError => _state(_channel).lastError;
   List<Drama> get dramas => _state(_channel).dramas;
   String? get cursor => _state(_channel).cursor;
   bool get hasMore => _state(_channel).hasMore;
   bool get loaded => _state(_channel).loaded;
   bool get loadingMore => _state(_channel).loadingMore;
-  bool get loadingFirstPage => !loaded;
+  bool get loadingFirstPage => !loaded && _state(_channel).loading;
 
   /// 用首页聚合接口打平的数据填充推荐首屏，不发起网络请求。
   void seedRecommend(List<Drama> dramas) {
@@ -42,27 +45,41 @@ class HomeFeedController extends ChangeNotifier {
       ..cursor = null
       ..hasMore = false
       ..loaded = true
-      ..loadingMore = false;
-    _lastError = null;
-    if (_channel == HomeFeedChannel.recommend) _notify();
+      ..loading = false
+      ..loadingMore = false
+      ..lastError = null
+      ..inFlight = null;
+    _notifyIfCurrent(HomeFeedChannel.recommend);
   }
 
-  /// 同步切到目标频道；有缓存先渲染，再在后台静默刷新。
+  /// 同步切到目标频道；有缓存先渲染，无缓存时复用或等待在飞请求。
   Future<void> selectChannel(HomeFeedChannel next) async {
     if (next == _channel) return;
     _channel = next;
-    _lastError = null;
     _notify();
     final state = _state(next);
     if (state.dramas.isNotEmpty) {
-      unawaited(_refresh(next, keepData: true));
-    } else {
-      await _loadFirst(next);
+      if (!state.loading) {
+        unawaited(_refresh(next, keepData: true));
+      }
+      return;
     }
+    if (state.loading) {
+      final inFlight = state.inFlight;
+      if (inFlight != null) await inFlight;
+      return;
+    }
+    await _refresh(next, keepData: false);
   }
 
   /// 刷新当前频道，失败时保留旧数据。
-  Future<bool> refreshCurrent() => _refresh(_channel, keepData: true);
+  Future<bool> refreshCurrent() async {
+    final state = _state(_channel);
+    if (state.loading) {
+      return await state.inFlight ?? false;
+    }
+    return _refresh(_channel, keepData: true);
+  }
 
   /// 加载当前频道下一页并去重追加。
   Future<void> loadMore() async {
@@ -71,14 +88,16 @@ class HomeFeedController extends ChangeNotifier {
     if (!state.hasMore || state.loadingMore || state.cursor == null) return;
     final seq = ++state.requestSeq;
     state.loadingMore = true;
-    _notify();
+    _notifyIfCurrent(channel);
     try {
-      final page = await _repository.fetchFeed(
-        types: channel.apiTypes,
-        cursor: state.cursor,
-        size: pageSize,
-      );
-      if (!_accept(channel, seq)) return;
+      final page = await _repository
+          .fetchFeed(
+            types: channel.apiTypes,
+            cursor: state.cursor,
+            size: pageSize,
+          )
+          .timeout(requestTimeout);
+      if (!_acceptSequence(channel, seq)) return;
       final seen = state.dramas.map((drama) => drama.id).toSet();
       final appended = page.dramas
           .where((drama) => seen.add(drama.id))
@@ -87,62 +106,78 @@ class HomeFeedController extends ChangeNotifier {
         ..dramas = List.unmodifiable([...state.dramas, ...appended])
         ..cursor = page.nextCursor
         ..hasMore = page.hasMore
-        ..loaded = true;
-      _lastError = null;
+        ..loaded = true
+        ..lastError = null;
     } catch (error) {
-      if (_accept(channel, seq)) _lastError = error.toString();
+      if (_acceptSequence(channel, seq)) {
+        state.lastError = error.toString();
+      }
     } finally {
       state.loadingMore = false;
-      if (_acceptChannel(channel)) _notify();
+      _notifyIfCurrent(channel);
     }
   }
 
-  Future<void> _loadFirst(HomeFeedChannel channel) async {
+  Future<bool> _refresh(HomeFeedChannel channel, {required bool keepData}) {
     final state = _state(channel);
-    state.loaded = false;
-    await _refresh(channel, keepData: state.dramas.isNotEmpty);
+    final operation = _performRefresh(channel, keepData: keepData);
+    state.inFlight = operation;
+    unawaited(_clearInFlight(state, operation));
+    return operation;
   }
 
-  Future<bool> _refresh(
+  Future<bool> _performRefresh(
     HomeFeedChannel channel, {
     required bool keepData,
   }) async {
     final state = _state(channel);
     final seq = ++state.requestSeq;
-    _lastError = null;
-    if (_acceptChannel(channel)) _notify();
+    state
+      ..loading = true
+      ..lastError = null;
+    _notifyIfCurrent(channel);
     try {
-      final page = await _repository.fetchFeed(
-        types: channel.apiTypes,
-        size: pageSize,
-      );
-      if (!_accept(channel, seq)) return false;
+      final page = await _repository
+          .fetchFeed(types: channel.apiTypes, size: pageSize)
+          .timeout(requestTimeout);
+      if (!_acceptSequence(channel, seq)) return false;
       state
         ..dramas = List.unmodifiable(page.dramas)
         ..cursor = page.nextCursor
         ..hasMore = page.hasMore
         ..loaded = true
-        ..loadingMore = false;
-      _lastError = null;
-      _notify();
+        ..loading = false
+        ..lastError = null;
+      _notifyIfCurrent(channel);
       return true;
     } catch (error) {
-      if (!_accept(channel, seq)) return false;
+      if (!_acceptSequence(channel, seq)) return false;
       if (!keepData) state.dramas = const [];
-      state.loaded = true;
-      _lastError = error.toString();
-      _notify();
+      state
+        ..loaded = true
+        ..loading = false
+        ..lastError = error.toString();
+      _notifyIfCurrent(channel);
       return false;
     }
   }
 
+  Future<void> _clearInFlight(
+    _ChannelFeedState state,
+    Future<bool> operation,
+  ) async {
+    await operation;
+    if (identical(state.inFlight, operation)) state.inFlight = null;
+  }
+
   _ChannelFeedState _state(HomeFeedChannel channel) => _states[channel]!;
 
-  bool _accept(HomeFeedChannel channel, int seq) =>
-      !_disposed && channel == _channel && _state(channel).requestSeq == seq;
+  bool _acceptSequence(HomeFeedChannel channel, int seq) =>
+      !_disposed && _state(channel).requestSeq == seq;
 
-  bool _acceptChannel(HomeFeedChannel channel) =>
-      !_disposed && channel == _channel;
+  void _notifyIfCurrent(HomeFeedChannel channel) {
+    if (!_disposed && channel == _channel) _notify();
+  }
 
   void _notify() {
     if (!_disposed) notifyListeners();
@@ -160,6 +195,9 @@ class _ChannelFeedState {
   String? cursor;
   bool hasMore = true;
   bool loaded = false;
+  bool loading = false;
   bool loadingMore = false;
+  String? lastError;
   int requestSeq = 0;
+  Future<bool>? inFlight;
 }