【flutter动画坑】一个组件多次不同的动画

import 'package:flutter/material.dart';

class TestPage extends StatefulWidget {
  _TestPageState createState() => new _TestPageState();
}

class _TestPageState extends State<TestPage> with TickerProviderStateMixin  {
  AnimationController controller;
  Animation<double> curve;
  Animation topAnimation;

  double _top = 0.0;
  int count = 0;
  
  @override
  void initState() {
    super.initState();
  }
  void startAnimation(begin, end) {
    controller = AnimationController(
        duration: const Duration(milliseconds: 600), vsync: this);
    curve = CurvedAnimation(parent: controller,curve: Curves.easeOut);
    topAnimation = Tween(begin: begin, end: end).animate(curve)
      ..addListener((){
        // print(topAnimation.value);
        // 一定要触发渲染不然最后就闪一闪到了终点
        setState(() {
          _top = topAnimation.value;
        });
      })
      ..addStatusListener((status) {
        if(status == AnimationStatus.completed) {
        	// 结束时操作
        }
      });
    controller.forward();
  }
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: <Widget>[
          Positioned(
            top: _top,
            child: FlutterLogo(),
          ),
          Positioned(
            bottom: 0,
            child: Container(
              width: 100,
              height: 100,
              child: RaisedButton(
                child: Text('点我'),
                onPressed: (){
                  count++;
                  setState(() {
                    count++;
                  });
                  startAnimation(_top, count*100.1);
                },
              ),
            ),
          )
        ],
      )
    );
  }

  dispose() {
    controller.dispose();
    super.dispose();
  }
}