后台连续播放 + MediaItem + 播放状态 + 实时进度 + 系统 seek + seek 后继续实时更新均已正常达成目标

lib/services/audio_player_handler.dart

@@ -81,20 +81,29 @@ class AudioPlayerHandler extends audio_service.BaseAudioHandler {
 
   void _publishStateOnly() {
     final current = playbackState.value;
-    // ⭐ 使用类成员 _currentPosition，不再重复声明
-    debugPrint(
-        '📡 [publishStateOnly] position=$_currentPosition, playing=${current.playing}');
 
-    playbackState.add(audio_service.PlaybackState(
-      controls: current.controls.isNotEmpty
-          ? current.controls
-          : _state.playbackState.controls,
-      processingState: _state.playbackState.processingState,
-      playing: current.playing,
-      androidCompactActionIndices: current.androidCompactActionIndices,
-      updatePosition: _currentPosition, // ⭐ 尝试加上
-      updateTime: DateTime.now(),
-    ));
+    debugPrint(
+      '📡 [publishStateOnly] position=$_currentPosition, playing=${current.playing}',
+    );
+
+    playbackState.add(
+      audio_service.PlaybackState(
+        controls: current.controls.isNotEmpty
+            ? current.controls
+            : _state.playbackState.controls,
+        processingState: _state.playbackState.processingState,
+        playing: current.playing,
+        androidCompactActionIndices: current.androidCompactActionIndices,
+
+        // ⭐ 声明支持 seek
+        systemActions: const {
+          audio_service.MediaAction.seek,
+        },
+
+        updatePosition: _currentPosition,
+        updateTime: DateTime.now(),
+      ),
+    );
   }
 
   void _updateMediaItem({