fix(player): 优化封面过渡与换集起播

test/player/player_opening_frame_test.dart

@@ -83,6 +83,34 @@ void main() {
 
     expect(find.byKey(const Key('player-opening-poster')), findsOneWidget);
   });
+
+  testWidgets('should_reuse_decoded_sprite_when_parent_rebuilds', (
+    tester,
+  ) async {
+    final loader = _FakeSpriteLoader();
+    final cache = OpeningFrameCache();
+    addTearDown(cache.clear);
+    Widget build() => MaterialApp(
+      home: PlayerOpeningFrame(
+        thumbnailsUrl: 'https://cdn.test/thumbnails.vtt',
+        posterUrl: 'https://cdn.test/poster.jpg',
+        loader: loader,
+        cache: cache,
+      ),
+    );
+
+    await tester.pumpWidget(build());
+    await tester.pumpAndSettle();
+    expect(loader.vttCalls, 1);
+    expect(loader.spriteCalls, hasLength(1));
+
+    await tester.pumpWidget(build());
+    await tester.pumpAndSettle();
+
+    expect(loader.vttCalls, 1);
+    expect(loader.spriteCalls, hasLength(1));
+    expect(find.byKey(const Key('player-opening-sprite')), findsOneWidget);
+  });
 }
 
 class _FakeSpriteLoader implements SpriteThumbnailAssetLoader {

test/player/player_video_surface_test.dart

@@ -30,6 +30,7 @@ void main() {
 
     expect(find.byKey(const Key('player-opening-frame')), findsOneWidget);
     expect(find.byKey(const Key('fake-opening')), findsOneWidget);
+    expect(_openingOpacity(tester), 1);
     expect(_opacity(tester), 0);
   });
 
@@ -48,7 +49,7 @@ void main() {
     expect(find.byKey(const Key('player-opening-frame')), findsNothing);
   });
 
-  testWidgets('should_fade_video_in_within_200ms_after_first_frame', (
+  testWidgets('should_cross_fade_video_over_opening_frame', (
     tester,
   ) async {
     final controller = await _pumpSurface(
@@ -67,7 +68,7 @@ void main() {
     await tester.pump();
 
     expect(_opacity(tester), 1);
-    expect(find.byKey(const Key('player-opening-frame')), findsNothing);
+    expect(find.byKey(const Key('player-opening-frame')), findsOneWidget);
     expect(
       tester
           .widget<AnimatedOpacity>(
@@ -80,8 +81,12 @@ void main() {
     final halfway = _fadeValue(tester);
     expect(halfway, greaterThan(0));
     expect(halfway, lessThan(1));
+    final openingHalfway = _openingFadeValue(tester);
+    expect(openingHalfway, greaterThan(0));
+    expect(openingHalfway, lessThan(1));
     await tester.pump(const Duration(milliseconds: 100));
     expect(_fadeValue(tester), 1);
+    expect(_openingFadeValue(tester), 0);
   });
 
   testWidgets('should_show_video_error_above_retained_fallback', (
@@ -182,6 +187,14 @@ double _opacity(WidgetTester tester) {
       .opacity;
 }
 
+double _openingOpacity(WidgetTester tester) {
+  return tester
+      .widget<AnimatedOpacity>(
+        find.byKey(const Key('player-opening-frame')),
+      )
+      .opacity;
+}
+
 double _fadeValue(WidgetTester tester) {
   final fade = find.descendant(
     of: find.byKey(const Key('player-video-opacity')),
@@ -189,3 +202,11 @@ double _fadeValue(WidgetTester tester) {
   );
   return tester.widget<FadeTransition>(fade).opacity.value;
 }
+
+double _openingFadeValue(WidgetTester tester) {
+  final fade = find.descendant(
+    of: find.byKey(const Key('player-opening-frame')),
+    matching: find.byType(FadeTransition),
+  );
+  return tester.widget<FadeTransition>(fade).opacity.value;
+}