试试这个代码，应该可以正常工作。

void main() {
  runApp(
    const MyApp(),
  );
}
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
      return MaterialApp(
        debugShowCheckedModeBanner: false,
        theme: ThemeData(useMaterial3: true),
        home: const HomePage(),
      );
    }
  }

'

此代码应该工作，试试看。

class MyApp extends StatelessWidget {
          @override
          Widget build(BuildContext context) {
            return MaterialApp(
              theme: ThemeData.light(useMaterial3: true),
              body: MyHomePage(),
            );
          }
        }