fix(player): 修复拖动进度条时加载态闪烁

test/playback/seek_progress_bar_test.dart

@@ -34,7 +34,9 @@ void main() {
     expect(find.byType(Slider), findsNothing);
   });
 
-  testWidgets('should_switch_between_loading_track_and_slider', (tester) async {
+  testWidgets('should_debounce_buffering_before_showing_loading_track', (
+    tester,
+  ) async {
     final video = ValueNotifier<VideoPlayerValue>(
       const VideoPlayerValue(
         duration: Duration(seconds: 12),
@@ -56,9 +58,17 @@ void main() {
       ),
     );
 
+    expect(find.byKey(const Key('progress-loading')), findsNothing);
+    expect(find.byType(Slider), findsOneWidget);
+    expect(find.textContaining('00:12'), findsNothing);
+
+    await tester.pump(const Duration(milliseconds: 200));
+    expect(find.byKey(const Key('progress-loading')), findsNothing);
+    expect(find.byType(Slider), findsOneWidget);
+
+    await tester.pump(const Duration(milliseconds: 200));
     expect(find.byKey(const Key('progress-loading')), findsOneWidget);
     expect(find.byType(Slider), findsNothing);
-    expect(find.textContaining('00:12'), findsNothing);
 
     video.value = const VideoPlayerValue(
       duration: Duration(seconds: 12),
@@ -71,6 +81,61 @@ void main() {
     expect(find.byType(Slider), findsOneWidget);
   });
 
+  testWidgets('should_keep_slider_while_scrubbing_during_buffering', (
+    tester,
+  ) async {
+    final video = ValueNotifier<VideoPlayerValue>(
+      const VideoPlayerValue(
+        duration: Duration(seconds: 12),
+        position: Duration(seconds: 3),
+        isInitialized: true,
+      ),
+    );
+    addTearDown(video.dispose);
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: SizedBox(
+              width: 300,
+              child: SeekProgressBar(
+                valueListenable: video,
+                semanticsLabel: 'Seek video',
+                onSeek: (_) async {},
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final gesture = await tester.startGesture(
+      tester.getCenter(find.byType(Slider)),
+    );
+    await gesture.moveBy(const Offset(60, 0));
+    await tester.pump();
+
+    video.value = const VideoPlayerValue(
+      duration: Duration(seconds: 12),
+      position: Duration(seconds: 5),
+      isInitialized: true,
+      isBuffering: true,
+    );
+    await tester.pump(const Duration(milliseconds: 400));
+
+    expect(find.byKey(const Key('progress-loading')), findsNothing);
+    expect(find.byType(Slider), findsOneWidget);
+
+    video.value = const VideoPlayerValue(
+      duration: Duration(seconds: 12),
+      position: Duration(seconds: 5),
+      isInitialized: true,
+    );
+    await tester.pump();
+    await gesture.up();
+    await tester.pumpAndSettle();
+  });
+
   testWidgets(
     'should_preview_while_dragging_and_seek_on_release_when_slider_is_horizontal',
     (tester) async {