Question

我有一个带有操作按钮的应用程序栏的外部支架，单击该按钮时，我想将内部有状态小部件的状态保存到烫发存储中-最好的方法是能够从内部调用内部小部件方法外部应用程序栏，还可以在调用的方法中执行Scaffold.of（context）吗？

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(....)
  }
}

Answer 1

您必须使外部类成为有状态的，并使内部类成为无状态的，或者使外部类的setState（）方法反映在内部类中。下面，我对您的示例进行了一些修改。

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;
      }
    }

Answer 2

这就是我最终得到的结果，它使我可以从应用程序栏按钮保存设置并显示小吃栏。在另一个带有选项卡式视图的组件中，我抬起了状态并将状态小部件传递到TabBarView子级小部件中，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),
    );
  }
}

从外部小部件保存状态

2 个答案: