我正在使用firebase创建一个登录-注册页面。但是当我运行main.dart时：

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
runApp(
MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (context) => AuthService()),
      ],
child:MyApp(
      )));} 

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

这是登录页面代码：

child: ElevatedButton(
  onPressed: () {
    if (formKey.currentState!.validate()) {
     if (isLogin) {
       login();
      } else {
       registrar();
     }
   }