How To Aniamation A Button Using Flutter Android App

import 'package:flutter/material.dart';
void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}
class MyHomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  //Uses a Ticker Mixin for Animations
  Animation<double> _animation;
  AnimationController _animationController;

  @override
  void initState() {
    super.initState();
    _animationController = AnimationController(
        vsync: this,
        duration: Duration(
            seconds:
            2));
    _animation = Tween<double>(begin: 1.0, end: 2.5).animate(
        _animationController);

    _animation.addListener(() {
      setState(() {});
    });

    _animation.addStatusListener((status) {
      if (status == AnimationStatus.completed) {
        _animationController
            .reverse();
      }
    });
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: Text('Animating A Button'),
      ),
      body: Center(
        child: ButtonTheme(
          minWidth: 88.0 *
              _animation
                  .value,
          height: 36.0 *
              _animation
                  .value,
          child: RaisedButton(
            textColor: Colors.white,
            child: Text('Tap to Animate Button'),
            onPressed: () {
              _animationController
                  .forward();
            },
            color: Colors.deepPurple[900],
          ),
        ),
      ),
    );
  }
}