从外部小部件保存状态
从外部小部件保存状态
提问于 2020-02-28 18:33:48
我有一个外部脚手架和一个带有操作按钮的应用程序栏，当单击它时，我希望将内部有状态小部件的状态保存到perm存储中-什么是能够从外部应用程序栏调用内部小部件方法并能够在调用的方法中执行Scaffold.of(上下文)的最佳方法？
class AISSettings extends StatelessWidget {
static const String route = 'settings/ais';
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('AIS settings'),
actions: <Widget>[
IconButton(icon: Icon(Icons.check), onPressed: () => {/* call _SettingsState.saveStuff() */} ),
],
),
bottomNavigationBar: Navbar(),
body: AISSettingsForm(),
);
}
}
class AISSettingsForm extends StatefulWidget {
@override
_SettingsState createState() => _SettingsState();
}
class _SettingsState extends State<AISSettingsForm> {
final _formKey = GlobalKey<_SettingsState>();
Map<String, dynamic> _options;
saveStuff() {
// Scaffold.of(context).showSnackBar(....)
}
}回答 2
Stack Overflow用户
发布于 2020-02-28 19:05:44
您必须使外部类是有状态的，而内部类是无状态的，或者是外部类setState()方法在内部类中反映的有状态的。下面我将提供一些修改后的示例。
class AISSettings extends StatefulWidget {
static const String route = 'settings/ais';
final _formKey = GlobalKey<_SettingsState>();
Map<String, dynamic> _options;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('AIS settings'),
actions: <Widget>[
IconButton(icon: Icon(Icons.check), onPressed: () => {/* call _SettingsState.saveStuff() */} ),
],
),
//bottomNavigationBar: Navbar(),
body: AISSettingsForm(),
);
}
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return null;
}
}
class AISSettingsForm extends StatefulWidget {
@override
_SettingsState createState() => _SettingsState();
}
class _SettingsState extends State<AISSettingsForm> {
saveStuff() {
// Scaffold.of(context).showSnackBar(....)
}
@override
Widget build(BuildContext context) {
// TODO: implement build
return null;
}
}Stack Overflow用户
发布于 2020-02-29 19:46:52
这就是我最终得到的，它允许我保存应用程序栏按钮中的设置，并显示一个快餐栏。在另一个带有选项卡式视图的组件中，我提升了状态，并将state小部件传递到TabBarView子小部件中，以便它们可以更新状态。
class AISSettings extends StatefulWidget {
static const String route = 'settings/ais';
@override
_SettingsState createState() => _SettingsState();
}
class _SettingsState extends State<AISSettings> {
final _formKey = GlobalKey<_SettingsState>();
Map<String, dynamic> _options;
saveStuff(context) {
// do stuff to save the settings to perm storage....
Scaffold.of(context).showSnackBar(....)
}
setValue(key, value) {
setState(() => _options[key] = value);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('AIS settings'),
actions: <Widget>[
Builder(
builder: (context) => IconButton(
icon: Icon(Icons.check),
onPressed: () => {saveStuff(context)}),
)
],
),
bottomNavigationBar: Navbar(),
body: ListView(
children: [
StatelessWidget1(this, _options),
StatelessWidget2(this, _options),
StatelessWidget3(this, _options),
])
);
}
}
class StatelessWidget1 extends StatelessWidget {
final Map<String, dynamic> settings;
final _SettingsState parent;
StatelessWidget1(this.parent, this.settings);
@override
Widget build(BuildContext context) {
return Slider(
key: Key('variation'),
min: -20.0,
max: 20.0,
label: '${settings['variation']}\u00B0',
divisions: 40,
value: 0.0 + settings['variation']
onChanged: (val) => parent.setValue('variation', val),
);
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/60449897
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