I keep getting this error The following _CastError was thrown building Builder: Null check operator used on a null value on my view after using the following code, I do not understand how to get around it. When I check in if statement for the empty email then obviously the value wont be null, so I added an !, why does it keep throwing this error? Can someone give advice?

  final TextEditingController _email = TextEditingController();
  final TextEditingController _password = TextEditingController();
  bool _isChecked = false;

  @override
  void initState() {
    super.initState();
    UserPreferences.init();
    if (UserPreferences.getEmail != '') {
      setState(() {
        _isChecked = true;
        _email.text = UserPreferences.getEmail!;
        _password.text = UserPreferences.getPassword!;
      });
    }
  }

class UserPreferences {
  static SharedPreferences? _preferences;

  static void init () async {
    _preferences = await SharedPreferences.getInstance();
  }

  static setEmail(String username) async {
    await _preferences?.setString('email', username);
  }

  static setPassword(String password) async {
    await _preferences?.setString('password', password);
  }

  static String? get getEmail => _preferences?.getString('email');
  static String? get getPassword => _preferences?.getString('password');

}

CodePudding user response：

Try this:

  static Future<void> init () async {
    _preferences = await SharedPreferences.getInstance();
  }

And initState should be like so:

  @override
  void initState() {
    super.initState();
    UserPreferences.init().then((_){
     if (UserPreferences.getEmail != '') {
      setState(() {
        _isChecked = true;
        _email.text = UserPreferences.getEmail!;
        _password.text = UserPreferences.getPassword!;
      });
    }
    });
  }

CodePudding user response：

When I check in if statement for the empty email then obviously the value wont be null

This is a wrong assumption. null != '' evaluates to true. Because in fact null is not an empty string