顺序播放跳曲与首次启动跳曲问题的metadata部分修复完成，测试已通过

lib/services/audio_service.dart

@@ -51,7 +51,7 @@ class AudioService extends ChangeNotifier {
   List<int> _shuffledIndices = [];
   int _shuffledIndex = -1;
 
-  // ---- 当前播放的歌单 ID（用于模式同步） ----
+  // ---- 当前播放的歌单 ID ----
   String? _currentPlaylistId;
 
   // ---- 高频进度 ----
@@ -68,7 +68,6 @@ class AudioService extends ChangeNotifier {
   bool _hasStartedCurrentPlayback = false;
   bool _isUserSeeking = false;
 
-  // ⭐ 播放代数：每次切歌递增，用于校验异步任务是否过期
   int _playbackGeneration = 0;
 
   void Function(Song)? _onSongChanged;
@@ -105,7 +104,6 @@ class AudioService extends ChangeNotifier {
     _onSongChanged = callback;
   }
 
-  // ---- 切换播放模式（同步更新歌单） ----
   void togglePlayMode() {
     switch (_playMode) {
       case PlayMode.sequential:
@@ -125,7 +123,10 @@ class AudioService extends ChangeNotifier {
     }
   }
 
-  // ---- 设置播放队列 ----
+  // ════════════════════════════════════════════════════════════
+  // 队列管理
+  // ════════════════════════════════════════════════════════════
+
   Future<void> setQueue(List<Song> queue, {int startIndex = 0}) async {
     if (queue.isEmpty) {
       _clearQueue();
@@ -160,7 +161,6 @@ class AudioService extends ChangeNotifier {
     stopPlay();
   }
 
-  // ---- 播放指定歌曲 ----
   Future<void> playSong(Song song) async {
     _currentPlaylistId = null;
     if (_queue.isEmpty || _queue[_currentIndex].id != song.id) {
@@ -171,7 +171,7 @@ class AudioService extends ChangeNotifier {
   }
 
   // ════════════════════════════════════════════════════════════
-  // 播放歌单
+  // 歌单
   // ════════════════════════════════════════════════════════════
 
   Future<void> playPlaylist(String playlistId, {int startIndex = 0}) async {
@@ -220,7 +220,7 @@ class AudioService extends ChangeNotifier {
   }
 
   // ════════════════════════════════════════════════════════════
-  // ⭐ 播放核心（完整生命周期控制）
+  // ⭐ 播放核心
   // ════════════════════════════════════════════════════════════
 
   Future<void> _playCurrent() async {
@@ -234,7 +234,6 @@ class AudioService extends ChangeNotifier {
       return;
     }
 
-    // ⭐ 进入切歌状态
     _isChangingTrack = true;
     _handlingCompletion = false;
     _hasStartedCurrentPlayback = false;
@@ -253,15 +252,11 @@ class AudioService extends ChangeNotifier {
         return;
       }
 
-      // ⭐ 关键：等待播放器加载完成
       await _playWithHeaders(song.url!);
-
-      // ⭐ 等待播放真正开始
       await _waitForPlaybackStarted();
 
       _syncPlayerStateDelayed();
 
-      // ⭐ 只有真正开始播放后才推送通知
       if (_hasStartedCurrentPlayback) {
         _onSongChanged?.call(song);
         _loadMetadataForCurrentSong(generation);
@@ -271,18 +266,15 @@ class AudioService extends ChangeNotifier {
     }
   }
 
-  /// ⭐ 等待播放器真正开始播放
   Future<void> _waitForPlaybackStarted() async {
     final player = PlaybackService().player;
 
-    // 如果已经在播放，直接标记
     if (player.state.playing) {
       _hasStartedCurrentPlayback = true;
       debugPrint('🎵 [AudioService] playback already started');
       return;
     }
 
-    // 等待 playing 变为 true，超时 3 秒
     try {
       await player.stream.playing
           .where((playing) => playing == true)
@@ -292,18 +284,15 @@ class AudioService extends ChangeNotifier {
       debugPrint('🎵 [AudioService] playback started');
     } catch (e) {
       debugPrint('⚠️ [AudioService] wait for playback timeout: $e');
-      // 超时也标记为已开始，避免永久阻塞
       _hasStartedCurrentPlayback = true;
     }
   }
 
-  /// ⭐ 播放带认证头的 URL
   Future<void> _playWithHeaders(String url) async {
     final headers = await _getAuthHeadersForUrl(url);
     await PlaybackService().play(url, headers: headers);
   }
 
-  /// ⭐ 获取 URL 对应的认证头（WebDAV 需要，本地文件不需要）
   Future<Map<String, String>> _getAuthHeadersForUrl(String url) async {
     if (url.startsWith('http://') || url.startsWith('https://')) {
       try {
@@ -324,6 +313,10 @@ class AudioService extends ChangeNotifier {
     return raw.hashCode.toString();
   }
 
+  // ════════════════════════════════════════════════════════════
+  // ⭐ Metadata 加载（四层校验）
+  // ════════════════════════════════════════════════════════════
+
   Future<void> _loadMetadataForCurrentSong(int generation) async {
     if (_currentIndex < 0 || _currentIndex >= _queue.length) return;
 
@@ -343,20 +336,32 @@ class AudioService extends ChangeNotifier {
         fileId: song.id,
       );
 
+      // 第一层：generation 校验
       if (_playbackGeneration != generation) {
-        debugPrint('⚠️ [AudioService] metadata stale (generation), ignoring');
+        debugPrint('⚠️ [AudioService] metadata stale (generation)');
-        return;
-      }
-      if (_currentIndex != currentIndex) {
-        debugPrint(
-            '⚠️ [AudioService] metadata stale (index changed), ignoring');
-        return;
-      }
-      if (currentIndex >= _queue.length || _queue[currentIndex].id != songId) {
-        debugPrint('⚠️ [AudioService] metadata stale (song changed), ignoring');
         return;
       }
 
+      // 第二层：索引校验
+      if (_currentIndex != currentIndex) {
+        debugPrint('⚠️ [AudioService] metadata stale (index changed)');
+        return;
+      }
+
+      // 第三层：歌曲 ID 校验
+      if (_currentIndex >= _queue.length ||
+          _queue[_currentIndex].id != songId) {
+        debugPrint('⚠️ [AudioService] metadata stale (song changed)');
+        return;
+      }
+
+      // ⭐ 第四层：_currentSong 校验（防止状态不同步）
+      if (_currentSong == null || _currentSong!.id != songId) {
+        debugPrint('⚠️ [AudioService] metadata stale: current song mismatch');
+        return;
+      }
+
+      if (metadata.isNotEmpty) {
         final updatedSong = Song(
           id: song.id,
           title: metadata.title.isNotEmpty ? metadata.title : song.title,
@@ -370,14 +375,14 @@ class AudioService extends ChangeNotifier {
 
         _onSongChanged?.call(updatedSong);
         debugPrint(
-          '✅ [AudioService] metadata updated: ${updatedSong.title} - ${updatedSong.artist} (generation $generation)');
+            '✅ [AudioService] metadata updated: ${updatedSong.title} - ${updatedSong.artist} (gen $generation)');
+      }
     } catch (e) {
-      debugPrint('⚠️ [AudioService] metadata load failed: $e, using fallback');
+      debugPrint('⚠️ [AudioService] metadata load failed: $e');
       _onSongChanged?.call(song);
     }
   }
 
-  /// 清除当前歌曲的缓存
   Future<void> clearCurrentSongCache() async {
     if (_currentSong == null) return;
     final song = _currentSong!;
@@ -433,10 +438,19 @@ class AudioService extends ChangeNotifier {
     }
   }
 
-  // ---- 下一首 ----
+  // ════════════════════════════════════════════════════════════
+  // ⭐ 上一首 / 下一首（带防并发）
+  // ════════════════════════════════════════════════════════════
+
   Future<void> next() async {
     if (_queue.isEmpty) return;
 
+    // ⭐ 如果正在切换歌曲，忽略本次请求
+    if (_isChangingTrack) {
+      debugPrint('⚠️ [AudioService] next() ignored: track switch in progress');
+      return;
+    }
+
     if (_playMode == PlayMode.shuffle) {
       if (_shuffledIndices.isEmpty) return;
       final nextIdx = (_shuffledIndex + 1) % _shuffledIndices.length;
@@ -451,10 +465,15 @@ class AudioService extends ChangeNotifier {
     await _playCurrent();
   }
 
-  // ---- 上一首 ----
   Future<void> previous() async {
     if (_queue.isEmpty) return;
 
+    if (_isChangingTrack) {
+      debugPrint(
+          '⚠️ [AudioService] previous() ignored: track switch in progress');
+      return;
+    }
+
     if (_playMode == PlayMode.shuffle) {
       if (_shuffledIndices.isEmpty) return;
       final prevIdx = (_shuffledIndex - 1) % _shuffledIndices.length;
@@ -592,26 +611,22 @@ class AudioService extends ChangeNotifier {
     // ⭐ 完整生命周期校验的 completed 监听
     _subscriptions.add(
       player.stream.completed.listen((_) {
-        // 第一层：切歌期间屏蔽
         if (_isChangingTrack) {
           debugPrint('⚠️ [AudioService] completed ignored during track switch');
           return;
         }
 
-        // 第二层：从未真正开始播放，忽略
         if (!_hasStartedCurrentPlayback) {
           debugPrint(
               '⚠️ [AudioService] completed ignored: playback never started');
           return;
         }
 
-        // 第三层：防重入
         if (_handlingCompletion) {
           debugPrint('⚠️ [service] completed ignored: already handling');
           return;
         }
 
-        // 第四层：额外校验 - 当前歌曲必须有有效的 duration
         final pos = player.state.position;
         final dur = player.state.duration;
         if (dur.inMilliseconds <= 0) {
@@ -620,10 +635,9 @@ class AudioService extends ChangeNotifier {
           return;
         }
 
-        // 第五层：位置必须接近歌曲末尾（允许 500ms 误差）
         if (pos.inMilliseconds < dur.inMilliseconds - 500) {
           debugPrint(
-              '⚠️ [AudioService] completed ignored: position=$pos, duration=$dur, not at end');
+              '⚠️ [AudioService] completed ignored: position=$pos, duration=$dur');
           return;
         }
 
@@ -643,16 +657,13 @@ class AudioService extends ChangeNotifier {
     _subscriptions.clear();
   }
 
-  // ---- 播放完成处理 ----
   void _onPlaybackCompleted() {
-    // 队列状态检查
     if (_queue.isEmpty || _currentIndex < 0 || _currentIndex >= _queue.length) {
       debugPrint('⚠️ [service] completed ignored: invalid queue');
       _handlingCompletion = false;
       return;
     }
 
-    // 如果是最后一首且不是单曲循环模式，不触发 next
     if (_currentIndex + 1 >= _queue.length && _playMode != PlayMode.repeatOne) {
       debugPrint('⚠️ [service] completed ignored: last song in queue');
       _handlingCompletion = false;