优化正在播放的自滑动刹车动画动作中

lib/pages/playlist_page.dart

@@ -14,12 +14,11 @@ class _PlaylistPageState extends State<PlaylistPage> {
   final ScrollController _scrollController = ScrollController();
   final GlobalKey _currentTagKey = GlobalKey();
 
-  bool _hasScrolledToCurrent = false;
-  int _retryCount = 0;
-  static const int _maxRetries = 3;
+  // ⭐ 定位事务 ID（防止旧任务污染）
+  int _scrollGeneration = 0;
 
-  // ⭐ 统一滚动时长 1.5 秒
-  static const Duration _scrollDuration = Duration(milliseconds: 1500);
+  // ⭐ 是否已完成定位
+  bool _hasScrolledToCurrent = false;
 
   @override
   void initState() {
@@ -35,18 +34,7 @@ class _PlaylistPageState extends State<PlaylistPage> {
     super.dispose();
   }
 
-  double _calculateAverageItemHeight(int itemCount) {
-    final maxExtent = _scrollController.position.maxScrollExtent;
-    if (maxExtent <= 0 || itemCount <= 0) return 72.0;
-    return maxExtent / itemCount;
-  }
-
-  double _calculateTargetOffset(
-      int currentIndex, int totalCount, double avgHeight) {
-    final viewportHeight = _scrollController.position.viewportDimension;
-    return (currentIndex * avgHeight) - (viewportHeight / 2) + (avgHeight / 2);
-  }
-
+  /// ⭐ 核心：一次计算 + 一次动画
   Future<void> _scrollToCurrentSong() async {
     if (_hasScrolledToCurrent) return;
 
@@ -58,97 +46,66 @@ class _PlaylistPageState extends State<PlaylistPage> {
       return;
     }
 
+    // 生成新的事务 ID，使旧任务失效
+    final generation = ++_scrollGeneration;
+
+    // 等待页面稳定
     await Future.delayed(const Duration(milliseconds: 300));
-    if (!mounted) return;
-
-    final totalCount = queue.length;
-    final avgHeight = _calculateAverageItemHeight(totalCount);
-    final maxExtent = _scrollController.position.maxScrollExtent;
+    if (!mounted || generation != _scrollGeneration) return;
 
+    // 获取目标 item 的当前布局状态
     var tagContext = _currentTagKey.currentContext;
-    if (tagContext != null) {
-      await _calibrateWithTag(tagContext);
-      _hasScrolledToCurrent = true;
-      return;
-    }
-
-    // ⭐ 粗定位：1.5 秒平滑滚动
-    final targetOffset =
-        _calculateTargetOffset(currentIndex, totalCount, avgHeight);
-    final clampedOffset = targetOffset.clamp(0.0, maxExtent);
-
-    await _scrollController.animateTo(
-      clampedOffset,
-      duration: _scrollDuration,
-      curve: Curves.easeOutCubic,
-    );
-    if (!mounted) return;
-
-    await WidgetsBinding.instance.endOfFrame;
-    if (!mounted) return;
-
-    tagContext = _currentTagKey.currentContext;
-    if (tagContext != null) {
-      await _calibrateWithTag(tagContext);
-      _hasScrolledToCurrent = true;
-      return;
-    }
-
-    // ⭐ 迭代修正：每次 1.5 秒平滑滚动
-    _retryCount = 0;
-    var currentOffset = _scrollController.offset;
-    var lastOffset = currentOffset;
-
-    while (_retryCount < _maxRetries) {
-      _retryCount++;
 
+    // ⭐ 如果 Tag 还没被构建，用不可见的 jumpTo 触发布局
+    if (tagContext == null) {
+      // 用 maxExtent 计算平均高度，做一次瞬时定位
+      final maxExtent = _scrollController.position.maxScrollExtent;
+      final avgHeight = maxExtent / queue.length;
       final viewportHeight = _scrollController.position.viewportDimension;
-      final step = viewportHeight * 0.5;
-      final direction = (currentIndex > totalCount / 2) ? -1 : 1;
-      final newOffset =
-          (currentOffset + direction * step).clamp(0.0, maxExtent);
+      final roughOffset =
+          (currentIndex * avgHeight) - (viewportHeight / 2) + (avgHeight / 2);
+      final clamped = roughOffset.clamp(0.0, maxExtent);
 
-      if ((newOffset - currentOffset).abs() < 50) {
-        final bigStep = viewportHeight * 0.8 * direction;
-        final forcedOffset = (currentOffset + bigStep).clamp(0.0, maxExtent);
-        await _scrollController.animateTo(
-          forcedOffset,
-          duration: _scrollDuration,
-          curve: Curves.easeOutCubic,
-        );
-      } else {
-        await _scrollController.animateTo(
-          newOffset,
-          duration: _scrollDuration,
-          curve: Curves.easeOutCubic,
-        );
-      }
-
-      if (!mounted) return;
+      // ⭐ 瞬时跳转（用户不可见）
+      _scrollController.jumpTo(clamped);
 
+      // 等待一帧，让目标 item 被构建
       await WidgetsBinding.instance.endOfFrame;
-      if (!mounted) return;
+      if (!mounted || generation != _scrollGeneration) return;
 
       tagContext = _currentTagKey.currentContext;
-      if (tagContext != null) {
-        await _calibrateWithTag(tagContext);
+
+      // 如果还是 null，说明估算偏差太大，用迭代方式推进
+      if (tagContext == null) {
+        // 最多尝试 2 次，每次推进半屏
+        for (int i = 0; i < 2; i++) {
+          final viewportHeight2 = _scrollController.position.viewportDimension;
+          final direction = (currentIndex > queue.length / 2) ? -1 : 1;
+          final step = viewportHeight2 * 0.7 * direction;
+          final newOffset = (_scrollController.offset + step)
+              .clamp(0.0, _scrollController.position.maxScrollExtent);
+          _scrollController.jumpTo(newOffset);
+          await WidgetsBinding.instance.endOfFrame;
+          if (!mounted || generation != _scrollGeneration) return;
+          tagContext = _currentTagKey.currentContext;
+          if (tagContext != null) break;
+        }
+        if (tagContext == null) {
           _hasScrolledToCurrent = true;
           return;
         }
-
-      currentOffset = _scrollController.offset;
-      if ((currentOffset - lastOffset).abs() < 10) break;
-      lastOffset = currentOffset;
+      }
     }
 
+    if (!mounted || generation != _scrollGeneration) return;
+
+    // ⭐ 获取 Tag 的真实位置
+    final renderBox = tagContext!.findRenderObject() as RenderBox?;
+    if (renderBox == null) {
       _hasScrolledToCurrent = true;
+      return;
     }
 
-  /// 精确定位：1.5 秒平滑滚动
-  Future<void> _calibrateWithTag(BuildContext tagContext) async {
-    final renderBox = tagContext.findRenderObject() as RenderBox?;
-    if (renderBox == null) return;
-
     final tagPosition = renderBox.localToGlobal(Offset.zero);
     final tagSize = renderBox.size;
     final tagCenter = tagPosition.dy + tagSize.height / 2;
@@ -161,13 +118,30 @@ class _PlaylistPageState extends State<PlaylistPage> {
     final targetOffset = (currentOffset + delta)
         .clamp(0.0, _scrollController.position.maxScrollExtent);
 
-    if ((targetOffset - currentOffset).abs() < 2) return;
+    // 如果偏差太小，直接标记完成
+    if ((targetOffset - currentOffset).abs() < 5) {
+      _hasScrolledToCurrent = true;
+      return;
+    }
 
+    // ⭐ 根据距离动态计算时长
+    final distance = (targetOffset - currentOffset).abs();
+    final durationMs = (250 + distance * 0.3).clamp(250, 700).round();
+    final duration = Duration(milliseconds: durationMs);
+
+    debugPrint(
+        '🎯 [定位] 距离: ${distance.toStringAsFixed(0)}px, 时长: ${durationMs}ms');
+
+    // ⭐ 唯一的一次可见动画
     await _scrollController.animateTo(
       targetOffset,
-      duration: _scrollDuration,
+      duration: duration,
       curve: Curves.easeOutCubic,
     );
+
+    if (mounted && generation == _scrollGeneration) {
+      _hasScrolledToCurrent = true;
+    }
   }
 
   @override