fix(home): 首切频道预取并保留播放画面

lib/core/data/services/home_feed_controller.dart

@@ -52,6 +52,14 @@ class HomeFeedController extends ChangeNotifier {
     _notifyIfCurrent(HomeFeedChannel.recommend);
   }
 
+  /// 后台预取漫剧与真人剧首屏，不切换频道，也不影响当前列表。
+  Future<void> prefetchChannels() async {
+    await Future.wait([
+      _prefetchChannel(HomeFeedChannel.anime),
+      _prefetchChannel(HomeFeedChannel.live),
+    ]);
+  }
+
   /// 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;
@@ -59,7 +67,9 @@ class HomeFeedController extends ChangeNotifier {
     _notify();
     final state = _state(next);
     if (state.dramas.isNotEmpty) {
-      if (!state.loading) {
+      if (state.skipNextRefresh) {
+        state.skipNextRefresh = false;
+      } else if (!state.loading) {
         unawaited(_refresh(next, keepData: true));
       }
       return;
@@ -67,6 +77,7 @@ class HomeFeedController extends ChangeNotifier {
     if (state.loading) {
       final inFlight = state.inFlight;
       if (inFlight != null) await inFlight;
+      state.skipNextRefresh = false;
       return;
     }
     await _refresh(next, keepData: false);
@@ -126,6 +137,13 @@ class HomeFeedController extends ChangeNotifier {
     return operation;
   }
 
+  Future<void> _prefetchChannel(HomeFeedChannel channel) async {
+    final state = _state(channel);
+    if (state.loaded || state.loading) return;
+    final success = await _refresh(channel, keepData: false);
+    if (success && !_disposed) state.skipNextRefresh = true;
+  }
+
   Future<bool> _performRefresh(
     HomeFeedChannel channel, {
     required bool keepData,
@@ -200,4 +218,5 @@ class _ChannelFeedState {
   String? lastError;
   int requestSeq = 0;
   Future<bool>? inFlight;
+  bool skipNextRefresh = false;
 }

lib/pages/home/home_view.dart

@@ -8,6 +8,7 @@ import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
 
 import '../../core/config/app_config.dart';
+import '../../core/data/models/drama.dart';
 import '../../core/data/services/home_feed_controller.dart';
 import '../../core/data/services/catalog_controller.dart';
 import '../../core/data/services/catalog_retry.dart';
@@ -141,7 +142,7 @@ class _HomePageState extends State<HomePage> with WidgetsBindingObserver {
       _recommendSeeded = true;
       homeFeed.seedRecommend(catalog.dramas);
       WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (mounted) unawaited(homeFeed.refreshCurrent());
+        if (mounted) unawaited(_refreshRecommendAndPrefetch(homeFeed));
       });
     }
     return _HomeTabs(key: const Key('home-tabs'), feedController: homeFeed);
@@ -151,6 +152,12 @@ class _HomePageState extends State<HomePage> with WidgetsBindingObserver {
     return _homeFeed ??= HomeFeedController(catalog.repository);
   }
 
+  Future<void> _refreshRecommendAndPrefetch(HomeFeedController homeFeed) async {
+    if (await homeFeed.refreshCurrent()) {
+      await homeFeed.prefetchChannels();
+    }
+  }
+
   Widget _startupSplash() {
     final isAndroid = defaultTargetPlatform == TargetPlatform.android;
     final size = isAndroid ? _androidSplashSize : _defaultSplashSize;
@@ -222,11 +229,15 @@ class _HomeTabs extends StatefulWidget {
 
 class _HomeTabsState extends State<_HomeTabs> {
   late final HomeLogic logic;
+  List<Drama>? _visibleDramas;
+  HomeFeedChannel? _visibleChannel;
 
   @override
   void initState() {
     super.initState();
     logic = HomeBinding().create(widget.feedController.dramas);
+    _visibleDramas = widget.feedController.dramas;
+    _visibleChannel = widget.feedController.channel;
     widget.feedController.addListener(_onFeedChanged);
   }
 
@@ -291,26 +302,70 @@ class _HomeTabsState extends State<_HomeTabs> {
   }
 
   Widget _home(BuildContext context) {
-    final dramas = widget.feedController.dramas;
-    if (dramas.isEmpty) return _feedChannelPlaceholder(context);
-    return PlayerPage(
-      homeMode: true,
-      embedded: true,
-      active: logic.tab == 0,
-      drama: dramas.first,
-      initialIndex: 0,
-      feedDramas: dramas,
-      feedChannel: widget.feedController.channel,
-      onOpenFullPlayer: (drama, episode) =>
-          logic.playDrama(context, drama, episodeId: episode.id),
-      onRefreshFeed: widget.feedController.refreshCurrent,
-      onLoadMore: widget.feedController.loadMore,
-      onChannelSelected: _selectFeedChannel,
-      onDramaChanged: logic.onDramaChanged,
-      onImmersiveChanged: logic.onImmersiveChanged,
-      onSearch: () => logic.select(1, search: true),
-      onDiscover: () => logic.select(1),
-      onMy: () => logic.select(3),
+    final currentDramas = widget.feedController.dramas;
+    final currentChannel = widget.feedController.channel;
+    if (currentDramas.isNotEmpty) {
+      _visibleDramas = currentDramas;
+      _visibleChannel = currentChannel;
+    }
+    if (currentDramas.isEmpty && !widget.feedController.loadingFirstPage) {
+      return _feedChannelPlaceholder(context);
+    }
+    final visibleDramas = _visibleDramas;
+    final visibleChannel = _visibleChannel;
+    final switching =
+        currentDramas.isEmpty && widget.feedController.loadingFirstPage;
+    if (visibleDramas == null ||
+        visibleDramas.isEmpty ||
+        visibleChannel == null) {
+      return _feedChannelPlaceholder(context);
+    }
+    final playerDramas = currentDramas.isEmpty ? visibleDramas : currentDramas;
+    final playerChannel = currentDramas.isEmpty
+        ? visibleChannel
+        : currentChannel;
+    return Stack(
+      fit: StackFit.expand,
+      children: [
+        PlayerPage(
+          homeMode: true,
+          embedded: true,
+          active: logic.tab == 0,
+          drama: playerDramas.first,
+          initialIndex: 0,
+          feedDramas: playerDramas,
+          feedChannel: playerChannel,
+          headerChannel: currentChannel,
+          onOpenFullPlayer: (drama, episode) =>
+              logic.playDrama(context, drama, episodeId: episode.id),
+          onRefreshFeed: widget.feedController.refreshCurrent,
+          onLoadMore: widget.feedController.loadMore,
+          onChannelSelected: _selectFeedChannel,
+          onDramaChanged: logic.onDramaChanged,
+          onImmersiveChanged: logic.onImmersiveChanged,
+          onSearch: () => logic.select(1, search: true),
+          onDiscover: () => logic.select(1),
+          onMy: () => logic.select(3),
+        ),
+        if (switching)
+          Positioned.fill(
+            child: IgnorePointer(
+              key: const Key('home-feed-channel-loading'),
+              child: ColoredBox(
+                color: Colors.black26,
+                child: Center(
+                  child: SizedBox.square(
+                    dimension: 24,
+                    child: CircularProgressIndicator(
+                      strokeWidth: 2.4,
+                      color: Colors.white70,
+                    ),
+                  ),
+                ),
+              ),
+            ),
+          ),
+      ],
     );
   }
 

lib/pages/player/player_view.dart

@@ -59,6 +59,7 @@ class PlayerPage extends StatefulWidget {
     this.onMenu,
     this.feedDramas,
     this.feedChannel,
+    this.headerChannel,
     this.onDramaChanged,
     this.onImmersiveChanged,
     this.onOpenFullPlayer,
@@ -82,6 +83,7 @@ class PlayerPage extends StatefulWidget {
   final VoidCallback? onMenu;
   final List<Drama>? feedDramas;
   final HomeFeedChannel? feedChannel;
+  final HomeFeedChannel? headerChannel;
   final ValueChanged<Drama>? onDramaChanged;
   final ValueChanged<bool>? onImmersiveChanged;
   final Future<void> Function(Drama drama, Episode episode)? onOpenFullPlayer;
@@ -295,7 +297,10 @@ class _PlayerPageState extends State<PlayerPage>
               bottom: false,
               child: HomeFeedHeader(
                 l10n: l10n,
-                channel: widget.feedChannel ?? HomeFeedChannel.recommend,
+                channel:
+                    widget.headerChannel ??
+                    widget.feedChannel ??
+                    HomeFeedChannel.recommend,
                 onChannelSelected: widget.onChannelSelected ?? (_) {},
                 onRefresh: () async {
                   final ok = await widget.onRefreshFeed?.call() ?? true;