how to expand menu in flutter code example

Example: how to expand menu in flutter

import 'package:flutter/material.dart';class Home extends StatelessWidget {  @override  Widget build(BuildContext context) {    return Scaffold(      appBar: AppBar(        title: Text(          'Flutter Expansion View',        ),        centerTitle: true,        elevation: 0.0,      ),      body: Padding(        padding: const EdgeInsets.symmetric(horizontal:30.0),        child: Column(          mainAxisAlignment: MainAxisAlignment.center,          children: <Widget>[            Row(              children: <Widget>[                Expanded(                  child: RaisedButton(                    onPressed: (){                      Navigator.push(                        context,                         MaterialPageRoute(                          builder: (BuildContext          context)=>Expansiontile()));                    },                    child: Text(                      'ExpansionTile'                    ),                  ),                ),              ],            ),            Row(              children: <Widget>[                Expanded(                  child: RaisedButton(                    onPressed: (){                      Navigator.push(                        context,                         MaterialPageRoute(                          builder: (BuildContext context)=>Expansionpanel()));                    },                    child: Text(                      'ExpansionPanel'                    ),                  ),                ),              ],            )          ],        ),      ),    );  }}