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| void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue,),
home: const MyHomePage(title: 'StatefulWidget 的简化'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var _switchValue = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const SizedBox(height: 20), //距离顶部距离
const Text('Flutter-Switch'),
_buildFlutterSwitch(),
const Text('ValueBuilder-Sample'),
_buildValueBuilder(),
const Text('ObxValue-Sample'),
_buildObxValue()
],
),
),
);
}
//FlutterBuilder
Widget _buildFlutterSwitch(){
return Switch(
value: _switchValue,
onChanged: (value) {
setState(() {
_switchValue = value;
});
});
}
//ValueBuilder
Widget _buildValueBuilder() {
return ValueBuilder<bool?>(
initialValue: false,
builder: (value, update) =>
Switch(value: value!, onChanged: (flag) => update(flag)),
onUpdate: (value) => print("Value updated: $value"),
onDispose: () => print("Widget unmounted"),
);
}
//ObxValue
Widget _buildObxValue() {
return ObxValue(
(data) => Switch(
value: (data as RxBool).value,
onChanged: (flag){
data.value=flag;
print("Value updated: $flag");
}, // Rx has a _callable_ function! You could use (flag) => data.value = flag,
),
false.obs,
);
}
}
|
