直接上代码，不懂就问嘛

import 'package:flutter/material.dart';

class AnimatedButton extends StatefulWidget {
  @override
  _AnimatedButtonState createState() => _AnimatedButtonState();
}

class _AnimatedButtonState extends State<AnimatedButton>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  late Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 1500),
    );
    _animation = Tween<double>(
      begin: 0.1,
      end: 5.2,
    ).animate(_controller)
      ..addListener(() {
        setState(() {});
      });

    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {

       _controller.forward();
      _animation.addStatusListener((status) {

        print(status);
        if (status == AnimationStatus.completed) {
          //缩小反向动画
          _controller.reverse();
          
        } else if (status == AnimationStatus.dismissed) {  //反向动画完成
          _controller.forward();
        }
      });
    });
  }

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

  void _onTapDown(TapDownDetails details) {
    // _controller.forward();

    print("_onTapDown");
  }

  void _onTapUp(TapUpDetails details) {
    // _controller.reverse();
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTapDown: _onTapDown,
      onTapUp: _onTapUp,
      onTapCancel: () => _controller.reverse(),
      child: Transform.scale(
        scale: _animation.value,
        child: Container(
          width: 100,
          height: 40,
          decoration: BoxDecoration(
            color: Colors.blue,
            borderRadius: BorderRadius.circular(20),
          ),
          child: Center(
            child: Text(
              'Click me!',
              style: TextStyle(
                color: Colors.white,
              ),
            ),
          ),
        ),
      ),
    );
  }
}