列表视图中的开关值出现问题颤振

Question

我在ListView中为每个元素创建一个Switch小部件。当我单击开关时，所有元素的值都会发生变化。 我检查颤振文档，飞镖文档...我想，我不会在 onChanged 方法中回收元素位置。

但是怎么做呢？

我的值是 切换 当我点击时更改。 当我喜欢时，我回收了法则，感谢：快照.数据[索引].name

主题屏幕 ：

class _ThemePage extends State<ThemePage> {
bool isSwitched = false;
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text("Blackbox"),
leading: Image.asset(
'assets/img/logo_ineat.png',
fit: BoxFit.contain,
height: 32,
),
),
body: new Center(
child: new Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
new Container(
margin: EdgeInsets.only(top: 10.0, bottom: 10.0),
child: new Text('Sélection du profil',
style: new TextStyle(
fontSize: 24, fontWeight: FontWeight.bold)),
alignment: Alignment.topCenter),
new Flexible(
child: new Container(
child: new FutureBuilder<List<t.Theme>>(
future: t.Theme().getThemes(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
if (snapshot.data != null) {
return new Column(
children: <Widget>[
new Expanded(
child: new ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, index) {
return ListTile(
title:
new Text(snapshot.data[index].name),
trailing: new Switch(
value: isSwitched,
activeColor: Colors.pink,
activeTrackColor: Colors.pinkAccent,
onChanged: (value){
setState(() {
isSwitched = value; 
if(value==true) {
print(snapshot.data[index].name);
}
});
},
),
);
},
),
),
],
);
}
} else {
new Text("Loading...");
return new CircularProgressIndicator();
}
}),
),
),
new Container(
margin: EdgeInsets.only(right: 10.0),
child: new RaisedButton.icon(
/*onPressed: () {
Navigator.pushReplacement(context,
MaterialPageRoute(builder: (context) => Technologies()));
},*/
label: Text('Suivant'),
icon: Icon(Icons.navigate_next),
),
alignment: Alignment.bottomRight,
),
],
),
),
);
}
}

Answer 1

您正在使用单个属性控制开关值isSwitched

您可以

• 创建另一个有状态的小部件，将您的开关逻辑放在那里(如果您想读取值，请使用回调((更干净(
• 创建布尔值列表而不是单个属性

使用第一个解决方案的代码：

class YourListViewItem extends StatefulWidget {
final String title;
const YourListViewItem({Key key, this.title}) : super(key: key);
@override
_YourListViewItemState createState() => _YourListViewItemState();
}
class _YourListViewItemState extends State<YourListViewItem> {
bool isSwitched = false;
@override
Widget build(BuildContext context) {
return ListTile(
title:
new Text(widget.title),
trailing: new Switch(
value: isSwitched,
activeColor: Colors.pink,
activeTrackColor: Colors.pinkAccent,
onChanged: (value){
setState(() {
isSwitched = value;
});
},
),
);
}
}

class _ThemePage extends State<ThemePage> {
bool isSwitched = false;
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text("Blackbox"),
leading: Image.asset(
'assets/img/logo_ineat.png',
fit: BoxFit.contain,
height: 32,
),
),
body: new Center(
child: new Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
new Container(
margin: EdgeInsets.only(top: 10.0, bottom: 10.0),
child: new Text('Sélection du profil',
style: new TextStyle(
fontSize: 24, fontWeight: FontWeight.bold)),
alignment: Alignment.topCenter),
new Flexible(
child: new Container(
child: new FutureBuilder<List<t.Theme>>(
future: t.Theme().getThemes(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
if (snapshot.data != null) {
return new Column(
children: <Widget>[
new Expanded(
child: new ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, index) {
return YourListViewItem(title: snapshot.data[index].name);
},
),
),
],
);
}
} else {
new Text("Loading...");
return new CircularProgressIndicator();
}
}),
),
),
new Container(
margin: EdgeInsets.only(right: 10.0),
child: new RaisedButton.icon(
/*onPressed: () {
Navigator.pushReplacement(context,
MaterialPageRoute(builder: (context) => Technologies()));
},*/
label: Text('Suivant'),
icon: Icon(Icons.navigate_next),
),
alignment: Alignment.bottomRight,
),
],
),
),
);
}
}