webdav存在自引用问题，现版本修复完成

lib/widgets/magnetic_scroll_controller.dart

@@ -0,0 +1,150 @@
+import 'package:flutter/material.dart';
+
+/// 磁吸进度状态
+class MagneticSnapState {
+  /// 吸附进度 0.0 ~ 1.0
+  final double progress;
+
+  /// 媒体库透明度
+  double get mediaOpacity {
+    // 0% ~ 70%: 1.0 → 0.45
+    // 70% ~ 100%: 0.45 → 0
+    if (progress <= 0.7) {
+      return 1.0 - (progress / 0.7) * 0.55;
+    } else {
+      final t = (progress - 0.7) / 0.3;
+      return 0.45 * (1 - t);
+    }
+  }
+
+  /// 收藏标题位移（从 +12px → 0）
+  double get favoriteTranslateY {
+    return (1 - progress) * 12;
+  }
+
+  /// 收藏列表展开程度 0.0 ~ 1.0
+  double get listReveal {
+    if (progress <= 0.7) return 0.0;
+    return (progress - 0.7) / 0.3;
+  }
+
+  /// 是否完全吸附
+  bool get isSnapped => progress >= 1.0;
+
+  /// 是否在磁吸区（进度 > 70%）
+  bool get isInMagneticZone => progress > 0.7;
+
+  const MagneticSnapState(this.progress);
+
+  factory MagneticSnapState.initial() => const MagneticSnapState(0.0);
+
+  MagneticSnapState copyWith({double? progress}) {
+    return MagneticSnapState(progress ?? this.progress);
+  }
+}
+
+/// 磁吸控制器
+class MagneticScrollController extends ChangeNotifier {
+  /// 吸附进度
+  double _progress = 0.0;
+  double get progress => _progress;
+
+  /// 是否已吸附
+  bool _isSnapped = false;
+  bool get isSnapped => _isSnapped;
+
+  /// 动画控制器（用于吸附动画）
+  AnimationController? _animationController;
+  TickerProvider? _tickerProvider;
+
+  /// 状态
+  MagneticSnapState get state => MagneticSnapState(_progress);
+
+  void init(TickerProvider vsync) {
+    _animationController = AnimationController(
+      vsync: vsync,
+      duration: const Duration(milliseconds: 300),
+    );
+  }
+
+  @override
+  void dispose() {
+    _animationController?.dispose();
+    super.dispose();
+  }
+
+  /// 更新滚动进度（在滚动时调用）
+  void updateProgress(double newProgress) {
+    if (_isSnapped) return;
+    _progress = newProgress.clamp(0.0, 1.0);
+    notifyListeners();
+  }
+
+  /// 处理松手事件
+  void onDragEnd(double velocity) {
+    if (_isSnapped) return;
+
+    final threshold = 0.45; // 45% 触发吸附
+    final shouldSnap = _progress > threshold || velocity > 800;
+
+    if (shouldSnap) {
+      snapOpen();
+    } else {
+      snapBack();
+    }
+  }
+
+  /// 吸附展开
+  void snapOpen() {
+    if (_isSnapped) return;
+    _isSnapped = true;
+
+    _animationController?.reset();
+    _animationController
+        ?.animateTo(
+      1.0,
+      duration: const Duration(milliseconds: 300),
+      curve: Curves.easeOutBack,
+    )
+        .then((_) {
+      _progress = 1.0;
+      notifyListeners();
+    });
+
+    // 实时更新进度
+    _animationController?.addListener(() {
+      _progress = _animationController!.value;
+      notifyListeners();
+    });
+  }
+
+  /// 回弹
+  void snapBack() {
+    if (_isSnapped) return;
+
+    _animationController?.reset();
+    _animationController
+        ?.animateTo(
+      0.0,
+      duration: const Duration(milliseconds: 250),
+      curve: Curves.easeOut,
+    )
+        .then((_) {
+      _progress = 0.0;
+      notifyListeners();
+    });
+
+    _animationController?.addListener(() {
+      _progress = _animationController!.value;
+      notifyListeners();
+    });
+  }
+
+  /// 重置状态（退出页面时）
+  void reset() {
+    _isSnapped = false;
+    _progress = 0.0;
+    _animationController?.reset();
+    notifyListeners();
+  }
+}

lib/widgets/magnetic_scroll_physics.dart

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+// lib/widgets/magnetic_scroll_physics.dart
+import 'package:flutter/material.dart';
+
+class MagneticScrollPhysics extends ClampingScrollPhysics {
+  final double snapPoint;
+  final double magneticZoneStart;
+
+  const MagneticScrollPhysics({
+    required this.snapPoint,
+    this.magneticZoneStart = 0.20,
+    super.parent,
+  });
+
+  @override
+  MagneticScrollPhysics applyTo(ScrollPhysics? ancestor) {
+    return MagneticScrollPhysics(
+      snapPoint: snapPoint,
+      magneticZoneStart: magneticZoneStart,
+      parent: buildParent(ancestor),
+    );
+  }
+
+  @override
+  Simulation? createBallisticSimulation(
+    ScrollMetrics position,
+    double velocity,
+  ) {
+    final offset = position.pixels;
+
+    if (offset <= 0 || offset >= snapPoint) {
+      return super.createBallisticSimulation(position, velocity);
+    }
+
+    final shouldSnap = _shouldSnap(offset, velocity);
+
+    final target = shouldSnap ? snapPoint : 0.0;
+
+    if ((offset - target).abs() < 1.0) {
+      return null;
+    }
+
+    return ScrollSpringSimulation(
+      SpringDescription(
+        mass: 1.0,
+        stiffness: 320.0,
+        damping: 26.0,
+      ),
+      offset,
+      target,
+      velocity,
+      tolerance: const Tolerance(
+        velocity: 0.01,
+        distance: 0.5,
+      ),
+    );
+  }
+
+  bool _shouldSnap(double offset, double velocity) {
+    final zoneStart = snapPoint * magneticZoneStart;
+
+    // 向上滑 → 吸附展开
+    if (velocity > 20) {
+      return true;
+    }
+
+    // 向下滑 → 回去
+    if (velocity < -20) {
+      return false;
+    }
+
+    // 松手速度很小，用当前位置决定
+    return offset >= zoneStart;
+  }
+}