初始化

2026-09-15 15:44:13 +07:00
commit a23ba685e9
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+import 'package:flutter/material.dart';
+
+/// 「加入购物车」式飞行动画：把某个组件的副本从原位置缩小飞到目标位置。
+///
+/// 挂在 Overlay 上而不是弹窗内部——先测量、再关弹窗、最后飞，这样蒙层干净消失，
+/// 飞行层浮在真实页面之上；放弹窗里做的话背景遮罩会一直压着，不像"收进去"。
+class FlyToOverlay {
+  FlyToOverlay._();
+
+  /// [context] 调用方(弹窗)的 context，用来找根 Overlay —— 不能用 Get.overlayContext，
+  /// 那拿到的是 Overlay 自身的 context，而 Overlay.of 只往祖先找，必然抛 "No Overlay widget found"
+  /// [sourceKey] 起飞组件（**必须在关闭弹窗前调用**，否则拿不到位置）
+  /// [target] 目标区域（屏幕坐标）；[child] 飞行途中显示的内容，通常是起飞组件的副本
+  static void play({
+    required BuildContext context,
+    required GlobalKey sourceKey,
+    required Rect target,
+    required Widget child,
+    Duration duration = const Duration(milliseconds: 700),
+  }) {
+    final box = sourceKey.currentContext?.findRenderObject() as RenderBox?;
+    if (box == null || !box.hasSize) return; // 量不到就不飞，不能因为动画报错
+    final begin = box.localToGlobal(Offset.zero) & box.size;
+
+    // rootOverlay：挂到最顶层，弹窗 pop 掉之后飞行层还得继续存活
+    final overlay = Overlay.maybeOf(context, rootOverlay: true);
+    if (overlay == null) return;
+
+    late OverlayEntry entry;
+    entry = OverlayEntry(
+      builder: (_) => _FlyView(
+        begin: begin,
+        end: target,
+        duration: duration,
+        // Overlay 被整体销毁时 entry 已不在树上，再 remove 会踩 assert
+        onDone: () {
+          if (entry.mounted) entry.remove();
+        },
+        child: child,
+      ),
+    );
+    overlay.insert(entry);
+  }
+}
+
+class _FlyView extends StatefulWidget {
+  final Rect begin;
+  final Rect end;
+  final Duration duration;
+  final VoidCallback onDone;
+  final Widget child;
+
+  const _FlyView({
+    required this.begin,
+    required this.end,
+    required this.duration,
+    required this.onDone,
+    required this.child,
+  });
+
+  @override
+  State<_FlyView> createState() => _FlyViewState();
+}
+
+class _FlyViewState extends State<_FlyView> with SingleTickerProviderStateMixin {
+  late final AnimationController _ctr = AnimationController(vsync: this, duration: widget.duration);
+
+  // easeInOutCubic：起步慢、中段快、**末尾减速**。不用 easeIn 系是因为那样末尾越飞越快，
+  // 到落点时一闪而过，用户来不及把弹窗和浮窗对应起来
+  late final Animation<Rect?> _rect = RectTween(begin: widget.begin, end: widget.end)
+      .animate(CurvedAnimation(parent: _ctr, curve: Curves.easeInOutCubic));
+
+  @override
+  void initState() {
+    super.initState();
+    _ctr.addStatusListener((s) {
+      if (s == AnimationStatus.completed) widget.onDone();
+    });
+    _ctr.forward();
+  }
+
+  @override
+  void dispose() {
+    _ctr.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedBuilder(
+      animation: _ctr,
+      builder: (_, child) {
+        final r = _rect.value ?? widget.begin;
+        // 全程基本保持不透明，只在最后 12% 收尾淡出：太早淡出会让人看不清落到哪儿了
+        final t = _ctr.value;
+        final opacity = t < 0.88 ? 1.0 : (1 - (t - 0.88) / 0.12).clamp(0.0, 1.0);
+        return Positioned(
+          left: r.left,
+          top: r.top,
+          width: r.width,
+          height: r.height,
+          child: IgnorePointer(
+            child: Opacity(opacity: opacity, child: child),
+          ),
+        );
+      },
+      // 内容按起飞尺寸渲染一次，交给 FittedBox 等比缩放，避免每帧重新布局图片
+      child: FittedBox(
+        fit: BoxFit.fill,
+        child: SizedBox(
+          width: widget.begin.width,
+          height: widget.begin.height,
+          child: widget.child,
+        ),
+      ),
+    );
+  }
+}