以下是一个示例，演示如何在按下一个小部件后将动画小部件返回到其之前的状态：

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Animation Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation _animation;

  @override
  void initState() {
    super.initState();

    // 初始化动画控制器
    _controller = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 500),
    );

    // 定义动画曲线（可选）
    final curve = CurvedAnimation(
      parent: _controller,
      curve: Curves.easeInOut,
    );

    // 定义动画范围和起始位置
    _animation = Tween(
      begin: Offset.zero,
      end: Offset(0.5, 0),
    ).animate(curve);
  }

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

  void _handleButtonPress() {
    if (_controller.isCompleted) {
      _controller.reverse(); // 当动画已完成时，反转动画
    } else {
      _controller.forward(); // 当动画未完成时，开始动画
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Animation Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            SlideTransition(
              position: _animation, // 使用动画
              child: Container(
                width: 200,
                height: 200,
                color: Colors.blue,
              ),
            ),
            SizedBox(height: 20),
            RaisedButton(
              onPressed: _handleButtonPress, // 按下按钮时触发动画
              child: Text('按下切换动画'),
            ),
          ],
        ),
      ),
    );
  }
}