我的应用程序有以下代码：

class LoginPage extends StatefulWidget {
  const LoginPage({Key? key}) : super(key: key);

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  String? errorMessage = '';
  bool isLogin = true;

  final TextEditingController _controllerEmail = TextEditingController();
  final TextEditingController _controllerPassword = TextEditingController();

  Future<void> signInWithEmailAndPassword() async {
    try {
      await Auth().signInWithEmailAndPassword(
          email: _controllerEmail.text, password: _controllerPassword.text);
    } on FirebaseAuthException catch (e) {
      setState(() {
        errorMessage = e.message;
      });
    }
  }

  Future<void> createUserWithEmailAndPassword() async {
    try {
      await Auth().createUserWithEmailAndPassword(
          email: _controllerEmail.text, password: _controllerPassword.text);
    } on FirebaseAuthException catch (e) {
      setState(() {
        errorMessage = e.message;
      });
    }
  }

  Widget _title() {
    return const Text("MysteryMap");
  }

  Widget _entryField(String title, TextEditingController controller) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: TextField(
        obscureText: title == 'contraseña' ? true : false,
        controller: controller,
        decoration: InputDecoration.collapsed(
          hintText: title,
        ),
      ),
    );
  }

  Widget _errorMessage() {
    return Text(
      errorMessage! == '' ? '' : '$errorMessage !!!',
      style: TextStyle(fontSize: 10, color: Colors.white),
    );
  }

  Widget _submitButton() {
    return ElevatedButton(
      onPressed: () => isLogin
          ? signInWithEmailAndPassword()
          : createUserWithEmailAndPassword(),
      child: Text(
        isLogin ? 'Iniciar sesión' : 'Crear cuenta',
        style: TextStyle(color: Colors.white),
      ),
    );
  }

  Widget _loginOrRegisterButton() {
    return TextButton(
        onPressed: () {
          setState(() {
            isLogin = !isLogin;
          });
        },
        child: Text(
          isLogin ? 'Crear cuenta' : 'Ya tengo cuenta',
          style: TextStyle(color: Colors.white),
        ));
  }

  @override
  Widget build(BuildContext context) {
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.portraitUp,
      DeviceOrientation.portraitDown,
    ]);
    return SafeArea(
      child: Scaffold(
        resizeToAvoidBottomInset: false,
        body: Container(
          width: double.infinity,
          height: double.infinity,
          decoration: BoxDecoration(
            image: DecorationImage(
              image: AssetImage("assets/fondo_login.jpeg"),
              fit: BoxFit.cover,
            ),
          ),
          padding: EdgeInsets.all(20),
          child: SingleChildScrollView(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisAlignment: MainAxisAlignment.start,
              children: [
                Row(
                  children: [
                    Container(
                      width: 80,
                      height: 80,
                      decoration: BoxDecoration(
                          image: DecorationImage(
                              image: AssetImage("assets/app_icon.png"))),
                    ),
                    Spacer(),
                  ],
                ),
                SizedBox(
                  height: 100,
                ),
                Align(
                    alignment: Alignment.topLeft,
                    child: Text(
                      "Email",
                      style: TextStyle(color: Colors.grey, fontSize: 18),
                    )),
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Container(
                      decoration: BoxDecoration(
                        color: Colors.white,
                        borderRadius: const BorderRadius.all(
                          Radius.circular(100.0),
                        ),
                      ),
                      child: _entryField('email', _controllerEmail)),
                ),
                SizedBox(
                  height: 10,
                ),
                Align(
                    alignment: Alignment.topLeft,
                    child: Text(
                      "Contraseña",
                      style: TextStyle(color: Colors.grey, fontSize: 18),
                    )),
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Container(
                      decoration: BoxDecoration(
                        color: Colors.white,
                        borderRadius: const BorderRadius.all(
                          Radius.circular(100.0),
                        ),
                      ),
                      child: _entryField('contraseña', _controllerPassword)),
                ),
                SizedBox(
                  height: 10,
                ),
                _errorMessage(),
                SizedBox(
                  height: 10,
                ),
                _submitButton(),
                SizedBox(
                  height: 10,
                ),
                _loginOrRegisterButton(),
                GestureDetector(
                    onTap: () {
                      Navigator.of(context).push(
                          MaterialPageRoute(builder: (context) => Plantilla()));
                    },
                    child: Text("fondo"))
              ],
            ),
          ),
        ),
      ),
    );
  }
}

大多数设备屏幕尺寸都没有问题。
问题出在小屏幕设备上，比如iPhone 7。当我想向第二个textField插入文本时，键盘隐藏了textField，屏幕没有滚动。

我应该在代码中更改或添加什么，以便在使用键盘编写文本时看到第二个textField？