如何在flutter中缩小和增长图标动画？

import 'package:flutter/material.dart';

AnimationController _controller;
Animation<double> _animation;

@override
void initState() {
  super.initState();
  _controller = AnimationController(
    duration: const Duration(seconds: 1),
    vsync: this,
  );
  _animation = Tween<double>(begin: 1.0, end: 0.5).animate(_controller);
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text('缩放动画'),
    ),
    body: Center(
      child: AnimatedBuilder(
        animation: _animation,
        builder: (BuildContext context, Widget child) {
          return Transform.scale(
            scale: _animation.value,
            child: Icon(
              Icons.favorite,
              size: 100.0,
              color: Colors.red,
            ),
          );
        },
      ),
    ),
    floatingActionButton: FloatingActionButton(
      onPressed: () {
        if (_controller.isCompleted) {
          _controller.reverse();
        } else {
          _controller.forward();
        }
      },
      child: Icon(Icons.play_arrow),
    ),
  );
}