Flutter -如何在自定义类小部件中更改变量

class MyCustomWidget extends StatefulWidget {
  @override
  _MyCustomWidgetState createState() => _MyCustomWidgetState();
}

class _MyCustomWidgetState extends State<MyCustomWidget> {
  String myVariable = '初始值';

  @override
  Widget build(BuildContext context) {
    return Container(
      child: RaisedButton(
        child: Text('更改变量'),
        onPressed: () {
          setState(() {
            myVariable = '新的值';
          });
        },
      ),
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter应用'),
        ),
        body: Center(
          child: MyCustomWidget(),
        ),
      ),
    );
  }
}