void main() async {
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
     future: Firebase.initializeApp(),
      builder: (context, snapshot) {
        return MaterialApp(
        ........
       );
  }
}

[core/no-app]未创建Firebase应用程序“[DEFAULT]”-调用Firebase.initializeApp（）另请参阅：https://flutter.dev/docs/testing/errors
然后当我使用

void main() async {
 WidgetsFlutterBinding.ensureInitialized();
 await Firebase.initializeApp();
  runApp(MyApp());
}

错误消失，但应用程序无法使用Firebase身份验证