backup. before shop update

lib/widgets/general/popup_animation_widget.dart

@@ -0,0 +1,70 @@
+import 'package:flutter/material.dart';
+
+// ignore: must_be_immutable
+class PopupAnimationWidget extends AnimatedWidget {
+  final GlobalKey stackKey;
+  final GlobalKey startKey;
+  final Color color;
+  final Widget child;
+  final Offset popupOffset;
+  final Animation<double> animation;
+
+  PopupAnimationWidget({
+    @required this.animation,
+    @required this.stackKey,
+    @required this.startKey,
+    @required this.child,
+    this.color = Colors.yellow,
+    this.popupOffset = Offset.zero,
+  }) : super(listenable: animation);
+
+  Offset _startOffset;
+  Offset _offset = Offset.zero;
+
+  @override
+  Widget build(BuildContext context) {
+    _calAnimation();
+
+    final Animation<double> opacityAnimation = Tween<double>(begin: 0, end: 1)
+        .animate(CurvedAnimation(
+        parent: animation, curve: Interval(0, 0.4, curve: Curves.ease)));
+    _offset =
+        Offset(_startOffset.dx, _startOffset.dy - opacityAnimation.value * 80);
+
+    return Positioned(
+      left: _offset.dx,
+      top: _offset.dy,
+      child: Opacity(
+        opacity: opacityAnimation.value,
+        child: ScaleTransition(
+          alignment: Alignment.bottomCenter,
+          scale: opacityAnimation,
+          child: Container(
+            child: child,
+          ),
+        ),
+      ),
+    );
+  }
+
+  void _calAnimation() {
+    if (_startOffset == null) {
+      final RenderBox stackBox = stackKey.currentContext.findRenderObject();
+      final Offset stackBoxOffset = stackBox.globalToLocal(Offset.zero);
+
+      final EdgeInsets startMargin = _margin(startKey);
+      final RenderBox startBox = startKey.currentContext.findRenderObject();
+
+      _startOffset = startBox.localToGlobal(Offset(
+          startMargin.left + popupOffset.dx,
+          stackBoxOffset.dy + startMargin.top + popupOffset.dy));
+    }
+  }
+
+  EdgeInsets _margin(GlobalKey key) {
+    final Widget widget = key.currentContext.widget;
+    final EdgeInsets margin =
+    (widget is Container) ? widget.margin : EdgeInsets.zero;
+    return margin ?? EdgeInsets.zero;
+  }
+}