flutter - 展开新的ExpansionTile时折叠ExpansionTile

Question

我试图解决这个问题几个小时，但是没有运气。我在这里看到过类似的问题，但它们似乎都不适合我的情况。这是简化的代码

static final List<String> _listViewData = [
    'Option1',
    'Option2',
    "Option3",
    "Option4",
    "Option5",
    "Option6",
    "Option7"
  ];


body: Container(
        height: 450,
        child: ListView.builder(
          itemCount: _listViewData.length,
          itemBuilder: (context, index) => ExpansionTile(
            subtitle: Text('description'),
            children: <Widget>[Text('expanded')],
            title: Text(_listViewData[index]),
          ),
        ),
      ),

到目前为止，当我从列表中选择Option1时，Option1将展开。然后，当我选择Option2时，Option2将展开，但Option1保持展开状态。那么，当新的瓷砖展开时，如何折叠展开的瓷砖？

Answer 1

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

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

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  // selected's value = 0. For default first item is open.
  int selected = 0; //attention

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,title: Text('ExpansionTile Collapse', style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold)),
      ),
      body: Container(color: Colors.white,
          child: SingleChildScrollView(
              child : Column( 
                children : [                  
                  ListView.builder(

                      key: Key('builder ${selected.toString()}'), //attention

                      padding: EdgeInsets.only(left: 13.0, right: 13.0, bottom: 25.0),
                      shrinkWrap: true,
                      physics: NeverScrollableScrollPhysics(),
                      itemCount: 5,
                      itemBuilder: (context, index) {                        
                        return Column(
                          children: <Widget>[
                            Divider(
                              height: 17.0,
                              color: Colors.white,
                            ), 
                                  ExpansionTile(  

                                        key: Key(index.toString()), //attention                                                                  
                                        initiallyExpanded : index==selected, //attention

                                        leading: Icon(Icons.person, size: 50.0, color: Colors.black,),
                                        title: Text('Faruk AYDIN ${index}',style: TextStyle(color: Color(0xFF09216B), fontSize: 17.0, fontWeight: FontWeight.bold)), 
                                        subtitle: Text('Software Engineer', style: TextStyle(color: Colors.black, fontSize: 13.0, fontWeight: FontWeight.bold),),
                                        children: <Widget>[                                       
                                          Padding(padding: EdgeInsets.all(25.0), 
                                                      child : Text('DETAİL ${index} \n' + 'It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using "Content here, content here", making it look like readable English.',)
                                                      ) 
                                        ],
                                        onExpansionChanged: ((newState){
                                            if(newState)
                                                setState(() {
                                                  Duration(seconds:  20000);
                                                  selected = index; 
                                                });
                                                else setState(() {
                                                  selected = -1; 
                                                });        
                                        })
                                      ),

                              ]
                            );
                      },
                        )
                ]
                    ),
          )           
        )
    );
  }
}