fix(player): 使用高清首帧并稳定切集占位

lib/pages/player/player_view.dart

@@ -127,6 +127,7 @@ class _PlayerPageState extends State<PlayerPage>
   DateTime? _lastDoubleTapAt;
   DateTime? _swipeStartedAt;
   bool _swipePrewarmCaptured = false;
+  final Set<String> _precachedPosterUrls = {};
 
   /// 收藏切换后的本地增量：基准是详情快照，切换成功按服务端状态 ±1。
   final Map<String, int> _favoriteDelta = {};
@@ -376,7 +377,7 @@ class _PlayerPageState extends State<PlayerPage>
     if (mounted) setState(() {});
   }
 
-  void _prewarmAdjacentThumbnails() {
+  void _prewarmAdjacentFrames() {
     final current = logic.session.currentIndex;
     final indices = <int?>[
       current,
@@ -387,9 +388,24 @@ class _PlayerPageState extends State<PlayerPage>
       if (index == null || index < 0 || index >= logic.sessionEpisodes.length) {
         continue;
       }
-      final thumbnailsUrl = logic.sessionEpisodes[index].thumbnailsUrl;
-      if (thumbnailsUrl != null &&
-          !logic.isEpisodeLocked(logic.sessionEpisodes[index])) {
+      final episode = logic.sessionEpisodes[index];
+      if (logic.isEpisodeLocked(episode)) continue;
+      final posterUrl = episode.posterUrl?.trim() ?? '';
+      if (posterUrl.isNotEmpty) {
+        final imageUrl = AppConfig.mediaUrl(posterUrl);
+        if (_precachedPosterUrls.add(imageUrl)) {
+          unawaited(
+            precacheImage(NetworkImage(imageUrl), context).catchError((
+              Object _,
+            ) {
+              _precachedPosterUrls.remove(imageUrl);
+            }),
+          );
+        }
+        continue;
+      }
+      final thumbnailsUrl = episode.thumbnailsUrl;
+      if (thumbnailsUrl != null && thumbnailsUrl.isNotEmpty) {
         unawaited(_spriteAxisService.prepareAt(thumbnailsUrl, Duration.zero));
       }
     }
@@ -477,7 +493,7 @@ class _PlayerPageState extends State<PlayerPage>
     final content = AnimatedBuilder(
       animation: logic.session,
       builder: (context, _) {
-        _prewarmAdjacentThumbnails();
+        _prewarmAdjacentFrames();
         final pages = NotificationListener<ScrollNotification>(
           onNotification: _handlePageScroll,
           child: PageView.builder(
@@ -592,12 +608,17 @@ class _PlayerPageState extends State<PlayerPage>
     final displayed = widget.homeMode
         ? logic.displayEpisode(drama, sessionEpisode)
         : sessionEpisode;
-    final episode =
+    final needsSessionThumbnails =
         (displayed.thumbnailsUrl == null || displayed.thumbnailsUrl!.isEmpty) &&
-            sessionEpisode.thumbnailsUrl != null
+        sessionEpisode.thumbnailsUrl != null;
+    final needsSessionPoster =
+        (displayed.posterUrl == null || displayed.posterUrl!.isEmpty) &&
+        sessionEpisode.posterUrl != null;
+    final episode = needsSessionThumbnails || needsSessionPoster
         ? displayed.withVideoUrl(
             displayed.videoUrl,
             thumbnailsUrl: sessionEpisode.thumbnailsUrl,
+            posterUrl: sessionEpisode.posterUrl,
           )
         : displayed;
     final selected = index == logic.session.currentIndex;
@@ -621,12 +642,19 @@ class _PlayerPageState extends State<PlayerPage>
     final theater = logic.pip || logic.pipPreparing;
     final videoFit = theater ? BoxFit.contain : BoxFit.cover;
     final preparedFrameAvailable =
-        selected && !locked && logic.session.reusedWarmAt(index);
+        !locked &&
+        videoReady &&
+        (selected
+            ? logic.session.reusedWarmAt(index)
+            : logic.session.preparedPlayerAt(index) != null);
+    final warmSlotReused = logic.session.reusedWarmAt(index);
     final thumbnailsUrl = episode.thumbnailsUrl;
+    final posterUrl = episode.posterUrl;
+    final posterReady = posterUrl?.trim().isNotEmpty ?? false;
     final openingFrameReady =
         thumbnailsUrl != null &&
         _spriteAxisService.cachedFrameAt(thumbnailsUrl, Duration.zero) != null;
-    if (thumbnailsUrl != null) {
+    if (!posterReady && thumbnailsUrl != null) {
       unawaited(_spriteAxisService.prepareAt(thumbnailsUrl, Duration.zero));
     }
     if (selected &&
@@ -654,7 +682,15 @@ class _PlayerPageState extends State<PlayerPage>
           videoUrl: videoPort?.controller.dataSource ?? episode.videoUrl,
           theater: theater,
           warmFrameAvailable: preparedFrameAvailable,
+          warmSlotReused: warmSlotReused,
           thumbnailReady: openingFrameReady,
+          posterReady: posterReady,
+          fallback: handoffPort != null
+              ? PlayerOpeningFallback.handoff
+              : playerOpeningFallback(
+                  posterUrl: posterUrl,
+                  thumbnailsUrl: thumbnailsUrl,
+                ),
           waitForPlaybackFrame: logic.session.userWantsPlay,
           placeholder: locked
               ? null
@@ -665,6 +701,7 @@ class _PlayerPageState extends State<PlayerPage>
                 )
               : playerOpeningFrame(
                   thumbnailsUrl,
+                  posterUrl: posterUrl,
                   spriteSource: _spriteAxisService,
                   fit: videoFit,
                 ),