AnimatedContainer - ClipPath + Flutter -路径未正确设置动画

import 'package:flutter/material.dart';

class AnimatedClipPathExample extends StatefulWidget {
  @override
  _AnimatedClipPathExampleState createState() => _AnimatedClipPathExampleState();
}

class _AnimatedClipPathExampleState extends State<AnimatedClipPathExample>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: Duration(seconds: 2),
      vsync: this,
    );
    _animation = Tween<double>(begin: 0, end: 1).animate(_controller);
    _controller.repeat(reverse: true);
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Animated ClipPath Example'),
      ),
      body: Center(
        child: AnimatedBuilder(
          animation: _animation,
          builder: (context, child) {
            return ClipPath(
              clipper: MyClipper(_animation.value),
              child: AnimatedContainer(
                duration: Duration(seconds: 1),
                width: 200,
                height: 200,
                color: Colors.blue,
              ),
            );
          },
        ),
      ),
    );
  }
}

class MyClipper extends CustomClipper<Path> {
  final double animationValue;

  MyClipper(this.animationValue);

  @override
  Path getClip(Size size) {
    Path path = Path();
    path.moveTo(size.width / 2, 0);
    path.lineTo(size.width, size.height * animationValue);
    path.lineTo(0, size.height * animationValue);
    path.close();
    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) {
    return true;
  }
}