如何在Flutter中绘制可展开和可折叠的侧边栏菜单？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Drawer Demo'),
        ),
        drawer: MyDrawer(),
        body: Center(
          child: Text('Home Page'),
        ),
      ),
    );
  }
}

class MyDrawer extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Drawer(
      child: ListView(
        padding: EdgeInsets.zero,
        children: <Widget>[
          DrawerHeader(
            child: Text('Menu'),
            decoration: BoxDecoration(
              color: Colors.blue,
            ),
          ),
          ListTile(
            title: Text('Item 1'),
            onTap: () {
              // 处理菜单项点击事件
            },
          ),
          ExpansionTile(
            title: Text('Item 2'),
            children: <Widget>[
              ListTile(
                title: Text('Subitem 1'),
                onTap: () {
                  // 处理子菜单项点击事件
                },
              ),
              ListTile(
                title: Text('Subitem 2'),
                onTap: () {
                  // 处理子菜单项点击事件
                },
              ),
            ],
          ),
        ],
      ),
    );
  }
}