更新复选框并从对话框抖动中返回值
我正在尝试将某些城市列表添加到带有复选框的对话框中，因此我需要对项目进行多次单击。我正在尝试做的事情在下面给出。
通过按钮 onPressed调用Rest Service，成功后我将显示一个对话框
void showCityDialog(BuildContext context) {
SimpleDialog dialog = new SimpleDialog(
title: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
new Text(
"CITIES",
style: TextStyle(fontSize: 18.0, color: Colors.black),
textAlign: TextAlign.center,
),
new RaisedButton(
onPressed: () {print("clicked");},
color: Color(0xFFfab82b),
child: new Text(
"Done",
style: TextStyle(color: Colors.white),
),)],),
children: <Widget>[
Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Container(
constraints: BoxConstraints(maxHeight: 500.0),
child: ListView.builder(
scrollDirection: Axis.vertical,
itemCount: cityData.length,
itemBuilder: (context, position) {
return new CheckboxListTile(
value: checkboxValueCity,
onChanged: (bool value) {
setState(() {
checkboxValueCity = value;
});
},
activeColor: Color(0xFFfab82b),
dense: true,
title: Text(
cityData[position].city_name,
style: TextStyle(fontSize: 16.0, color: Colors.black),
),);},),),],)],);
showDialog(
context: context,
builder: (BuildContext context) {
return dialog;
});
}
checkboxValueCity是类中的一个布尔变量，在点击chekboxListItem时，我需要更新选中和未选中的复选框的值。同时需要将该项目添加/删除到该类内的列表中。
但是在我的代码中，复选框并不是每次单击都引用，而是在我关闭该框并再次打开时选中该复选框。那么我如何才能从图块中获得多次点击？如何从对话中返回列表？
4 个答案:
答案 0 :(得分：8)
使用StatefulBuilder仅在Dialog内部更新小部件。 StatefulBuilder最适合小部件树的更新部分，其中
状态是必需的。
简单代码段
void _showDialog() {
showDialog(
context: context,
builder: (context) {
return StatefulBuilder( // StatefulBuilder
builder: (context, setState) {
return AlertDialog(
actions: <Widget>[
Container(
width: 400,
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Text(
"Student Attendence",
style: TextStyle(fontSize: 20),
),
SizedBox(
height: 5,
),
Container(
height: 2,
color: Colors.black,
),
SizedBox(
height: 15,
),
CheckboxListTile(
value: user1,
title: Text("user1"),
onChanged: (value){
setState(() {
user1=value;
});
},
),
Divider(
height: 10,
),
CheckboxListTile(
value: user2,
title: Text("user2"),
onChanged: (value){
setState(() {
user2=value;
});
},
),
Divider(
height: 10,
),
CheckboxListTile(
value: user3,
title: Text("user3"),
onChanged: (value){
setState(() {
user3=value;
});
},
),
Divider(
height: 10,
),
CheckboxListTile(
value: user4,
title: Text("user4"),
onChanged: (value){
setState(() {
user4=value;
});
},
),
Divider(
height: 10,
),
SizedBox(
height: 5,
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Material(
elevation: 5.0,
color: Colors.blue[900],
child: MaterialButton(
padding: EdgeInsets.fromLTRB(
10.0, 5.0, 10.0, 5.0),
onPressed: () {},
child: Text("Save",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontSize: 15,
)),
),
),
Material(
elevation: 5.0,
color: Colors.blue[900],
child: MaterialButton(
padding: EdgeInsets.fromLTRB(
10.0, 5.0, 10.0, 5.0),
onPressed: () {
setState(() {
Navigator.of(context).pop();
});
},
child: Text("Cancel",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontSize: 15,
)),
),
),
Material(
elevation: 5.0,
color: Colors.blue[900],
child: MaterialButton(
padding: EdgeInsets.fromLTRB(
10.0, 5.0, 10.0, 5.0),
onPressed: () {},
child: Text("Select All",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontSize: 15,
)),
),
),
],
)
],
))
],
);
},
);
},
);
}
示例
答案 1 :(得分：6)
您的对话框必须为StatefulWidget（Flutter Github issue）。跟踪选择状态的成员变量必须在对话框类中。您可以使用回调来使用所选城市的List更新父类中的成员变量。在ListView.builder或SimpleDialog内使用AlertDialog似乎也存在一些问题（在Flutter Github上搜索问题），所以我使用了普通的Dialog。
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Checkbox Dialog Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Checkbox Dialog Demo'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
bool checkboxValueCity = false;
List<String> allCities = ['Alpha', 'Beta', 'Gamma'];
List<String> selectedCities = [];
@override
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {
showDialog(
context: context,
builder: (context) {
return _MyDialog(
cities: allCities,
selectedCities: selectedCities,
onSelectedCitiesListChanged: (cities) {
selectedCities = cities;
print(selectedCities);
});
});
}),
);
}
}
class _MyDialog extends StatefulWidget {
_MyDialog({
this.cities,
this.selectedCities,
this.onSelectedCitiesListChanged,
});
final List<String> cities;
final List<String> selectedCities;
final ValueChanged<List<String>> onSelectedCitiesListChanged;
@override
_MyDialogState createState() => _MyDialogState();
}
class _MyDialogState extends State<_MyDialog> {
List<String> _tempSelectedCities = [];
@override
void initState() {
_tempSelectedCities = widget.selectedCities;
super.initState();
}
@override
Widget build(BuildContext context) {
return Dialog(
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
'CITIES',
style: TextStyle(fontSize: 18.0, color: Colors.black),
textAlign: TextAlign.center,
),
RaisedButton(
onPressed: () {
Navigator.pop(context);
},
color: Color(0xFFfab82b),
child: Text(
'Done',
style: TextStyle(color: Colors.white),
),
),
],
),
Expanded(
child: ListView.builder(
itemCount: widget.cities.length,
itemBuilder: (BuildContext context, int index) {
final cityName = widget.cities[index];
return Container(
child: CheckboxListTile(
title: Text(cityName),
value: _tempSelectedCities.contains(cityName),
onChanged: (bool value) {
if (value) {
if (!_tempSelectedCities.contains(cityName)) {
setState(() {
_tempSelectedCities.add(cityName);
});
}
} else {
if (_tempSelectedCities.contains(cityName)) {
setState(() {
_tempSelectedCities.removeWhere(
(String city) => city == cityName);
});
}
}
widget
.onSelectedCitiesListChanged(_tempSelectedCities);
}),
);
}),
),
],
),
);
}
}
答案 2 :(得分：1)
尽管阿尔伯特的答案奏效，但您不必一路走下去。只需用StatefulBuilder包装内容：，瞧！ https://api.flutter.dev/flutter/widgets/StatefulBuilder-class.html。
注意：在声明要更改的变量的地方很重要。
答案 3 :(得分：0)
我稍微修改了您的代码，我希望当用户检查列表时，列表不会更新到主视图，但是当用户单击“更新”按钮时，它们会更新。 但是有些方法却行不通。你能检查一下吗？ 非常感谢
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Checkbox Dialog Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Checkbox Dialog Demo'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
bool checkboxValueCity = false;
List<String> allCities = ['Alpha', 'Beta', 'Gamma'];
List<String> selectedCities = [];
List<String> selectedCitiesTemp = [];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("App Bar"),
),
body: Center(
child: Column(
children: <Widget>[
_list(),
RaisedButton(
child: Text("Update From TMP List"),
onPressed: () {
setState(() {
selectedCities = selectedCitiesTemp;
});
},
)
],
),
),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {
showDialog(
context: context,
builder: (BuildContext context) {
return _MyDialog(
cities: allCities,
selectedCities: selectedCities,
onSelectedCitiesListChanged: (cities) {
setState(() {
selectedCitiesTemp = cities;
});
},
);
});
}),
);
}
Widget _list() {
List<Widget> list = [];
for(String item in selectedCities) {
list.add(ListTile(
title: Text(item),
));
}
return Column(
children: list
);
}
}
class _MyDialog extends StatefulWidget {
_MyDialog({
this.cities,
this.selectedCities,
this.onSelectedCitiesListChanged,
});
final List<String> cities;
final List<String> selectedCities;
final ValueChanged<List<String>> onSelectedCitiesListChanged;
@override
_MyDialogState createState() => _MyDialogState();
}
class _MyDialogState extends State<_MyDialog> {
List<String> _tempSelectedCities = [];
@override
void initState() {
_tempSelectedCities = widget.selectedCities;
super.initState();
}
@override
Widget build(BuildContext context) {
return Dialog(
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
'CITIES',
style: TextStyle(fontSize: 18.0, color: Colors.black),
textAlign: TextAlign.center,
),
],
),
Expanded(
child: ListView.builder(
itemCount: widget.cities.length,
itemBuilder: (BuildContext context, int index) {
final cityName = widget.cities[index];
return Container(
child: CheckboxListTile(
title: Text(cityName),
value: _tempSelectedCities.contains(cityName),
onChanged: (bool value) {
if (value) {
if (!_tempSelectedCities.contains(cityName)) {
setState(() {
_tempSelectedCities.add(cityName);
});
}
} else {
if (_tempSelectedCities.contains(cityName)) {
setState(() {
_tempSelectedCities.removeWhere(
(String city) => city == cityName);
});
}
}
widget.onSelectedCitiesListChanged(_tempSelectedCities);
}),
);
}),
),
],
),
);
}
}
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