如何在Flutter中单击另一个扩展磁贴后折叠已打开的扩展磁贴？

import 'package:flutter/material.dart';

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

class _MyHomePageState extends State<MyHomePage> {
  int _expandedTileIndex = -1;

  void _handleTileTap(int index) {
    setState(() {
      if (_expandedTileIndex == index) {
        _expandedTileIndex = -1; // 当前扩展磁贴已经展开，再次点击则折叠
      } else {
        _expandedTileIndex = index; // 展开新的扩展磁贴
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('可折叠的扩展磁贴'),
      ),
      body: ListView.builder(
        itemCount: 5, // 假设有5个扩展磁贴
        itemBuilder: (context, index) {
          return ExpansionTile(
            title: Text('磁贴 $index'),
            children: <Widget>[
              ListTile(
                title: Text('内容 $index'),
              ),
            ],
            onExpansionChanged: (expanded) {
              _handleTileTap(index);
            },
            initiallyExpanded: _expandedTileIndex == index,
          );
        },
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyHomePage(),
  ));
}