如何在CustomPainter中添加fling动画？

import 'package:flutter/material.dart';

class MyCustomPainter extends CustomPainter {
  AnimationController _controller;
  Animation<double> _animation;

  MyCustomPainter(this._controller)
      : _animation = Tween(begin: 0.0, end: 1.0).animate(_controller);

  @override
  void paint(Canvas canvas, Size size) {
    // 根据_animation.value绘制相应的图形或效果
    // 示例：绘制一个矩形
    final rect = Rect.fromLTWH(
      size.width / 2 - 50 * _animation.value,
      size.height / 2 - 50 * _animation.value,
      100 * _animation.value,
      100 * _animation.value,
    );
    final paint = Paint()..color = Colors.blue;
    canvas.drawRect(rect, paint);
  }

  @override
  bool shouldRepaint(MyCustomPainter oldDelegate) => true;
}

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 500),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanUpdate: (details) {
        // 根据手势滑动的距离更新动画的值
        _controller.value -= details.delta.dx / context.size.width;
      },
      onPanEnd: (details) {
        // 根据动画的值和速度计算出最终的动画结果，并启动动画
        if (_controller.isAnimating ||
            _controller.status == AnimationStatus.completed) return;
        final flingVelocity = details.velocity.pixelsPerSecond.dx / context.size.width;
        _controller.fling(velocity: flingVelocity);
      },
      child: CustomPaint(
        painter: MyCustomPainter(_controller),
        child: Container(),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      body: Center(
        child: MyWidget(),
      ),
    ),
  ));
}