flutter4.dart

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: MyScaffold());
  }
}

class MyScaffold extends StatelessWidget {
  const MyScaffold({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Title')),
      body: Center(child: Text('Hello World')),
      floatingActionButton: FloatingActionButton(
        onPressed: () => print('Button pressed'),
        child: Icon(Icons.add),
      ),
    );
  }
}