feat(player): 未就绪改由进度条展示加载态

test/playback/seek_progress_bar_test.dart

@@ -16,55 +16,111 @@ void main() {
     expect(seekPositionForFraction(1, duration), lessThan(duration));
   });
 
-  testWidgets('should_preview_while_dragging_and_seek_on_release_when_slider_is_horizontal', (
+  testWidgets('should_show_loading_track_when_controller_is_missing', (
     tester,
   ) async {
-    final video = ValueNotifier<VideoPlayerValue>(
-      const VideoPlayerValue(
-        duration: Duration(seconds: 12),
-        position: Duration(seconds: 3),
-        isInitialized: true,
-      ),
-    );
-    addTearDown(video.dispose);
-    var started = 0;
-    Duration? target;
     await tester.pumpWidget(
       MaterialApp(
         home: Scaffold(
-          body: Center(
-            child: SizedBox(
-              width: 300,
-              child: SeekProgressBar(
-                valueListenable: video,
-                semanticsLabel: 'Seek video',
-                onScrubStart: () => started++,
-                onSeek: (position) async {
-                  target = position;
-                },
-              ),
-            ),
+          body: SeekProgressBar(
+            valueListenable: null,
+            semanticsLabel: 'Seek video',
           ),
         ),
       ),
     );
 
-    final gesture = await tester.startGesture(
-      tester.getCenter(find.byType(Slider)),
-    );
-    await gesture.moveBy(const Offset(120, 0));
-    await tester.pump();
-    expect(started, 1);
-    expect(target, isNull);
-    expect(find.textContaining('/ 00:12'), findsOneWidget);
-    await gesture.up();
-    await tester.pumpAndSettle();
-    expect(target, isNotNull);
-    expect(target!, greaterThan(const Duration(seconds: 3)));
-    expect(target!, lessThan(const Duration(seconds: 12)));
-    expect(find.textContaining('/ 00:12'), findsNothing);
+    expect(find.byKey(const Key('progress-loading')), findsOneWidget);
+    expect(find.byType(Slider), findsNothing);
   });
 
+  testWidgets('should_switch_between_loading_track_and_slider', (tester) async {
+    final video = ValueNotifier<VideoPlayerValue>(
+      const VideoPlayerValue(
+        duration: Duration(seconds: 12),
+        position: Duration(seconds: 3),
+        isInitialized: true,
+        isBuffering: true,
+      ),
+    );
+    addTearDown(video.dispose);
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: SeekProgressBar(
+            valueListenable: video,
+            semanticsLabel: 'Seek video',
+            onSeek: (_) async {},
+          ),
+        ),
+      ),
+    );
+
+    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),
+      position: Duration(seconds: 3),
+      isInitialized: true,
+    );
+    await tester.pump();
+
+    expect(find.byKey(const Key('progress-loading')), findsNothing);
+    expect(find.byType(Slider), findsOneWidget);
+  });
+
+  testWidgets(
+    'should_preview_while_dragging_and_seek_on_release_when_slider_is_horizontal',
+    (tester) async {
+      final video = ValueNotifier<VideoPlayerValue>(
+        const VideoPlayerValue(
+          duration: Duration(seconds: 12),
+          position: Duration(seconds: 3),
+          isInitialized: true,
+        ),
+      );
+      addTearDown(video.dispose);
+      var started = 0;
+      Duration? target;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: Center(
+              child: SizedBox(
+                width: 300,
+                child: SeekProgressBar(
+                  valueListenable: video,
+                  semanticsLabel: 'Seek video',
+                  onScrubStart: () => started++,
+                  onSeek: (position) async {
+                    target = position;
+                  },
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+
+      final gesture = await tester.startGesture(
+        tester.getCenter(find.byType(Slider)),
+      );
+      await gesture.moveBy(const Offset(120, 0));
+      await tester.pump();
+      expect(started, 1);
+      expect(target, isNull);
+      expect(find.textContaining('/ 00:12'), findsOneWidget);
+      await gesture.up();
+      await tester.pumpAndSettle();
+      expect(target, isNotNull);
+      expect(target!, greaterThan(const Duration(seconds: 3)));
+      expect(target!, lessThan(const Duration(seconds: 12)));
+      expect(find.textContaining('/ 00:12'), findsNothing);
+    },
+  );
+
   testWidgets('should_show_time_only_while_dragging_when_seek_bar_is_compact', (
     tester,
   ) async {