如何在Flutter中真正使用SizeTransition？

import 'package:flutter/material.dart';

class MySizeTransitionWidget extends StatefulWidget {
  @override
  _MySizeTransitionWidgetState createState() => _MySizeTransitionWidgetState();
}

class _MySizeTransitionWidgetState extends State<MySizeTransitionWidget>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

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

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

  @override
  Widget build(BuildContext context) {
    return Container(
      child: SizeTransition(
        sizeFactor: _animation,
        axisAlignment: 0.0,
        child: // 子组件,
      ),
    );
  }
}

_controller.forward(); // 正向播放动画
_controller.reverse(); // 反向播放动画