I'm a new flutter user here, so this time I have a problem when I login with API SERVICE, the login says

_CastError (Null check operator used on a null value)

the error is in the use of the source as below

Future<void> login(BuildContext context) async {
    AppFocus.unfocus(context);
    if (loginFormKey.currentState!.validate()) {
      final LoginResponse? res = await apiRepository.login(
        LoginRequest(
          email: loginEmailController.text,
          password: loginPasswordController.text,
        ),
      );

      final SharedPreferences prefs = Get.find<SharedPreferences>();

      if (res!.accessToken.isNotEmpty) {
        prefs.setString(StorageConstants.token, res.accessToken);
        Get.toNamed(Routes.HOME);
        Get.snackbar("Berhasil", "Selamat Berhasil Login");
      } else {
        Get.snackbar("title", "coab");
      }
    }
  }

exactly the error appears in this section

if (res!.accessToken.isNotEmpty)

CodePudding user response：

final LoginResponse? res you declare with ? which means res is nullable value.

but if (res!.accessToken.isNotEmpty) you use ! which means, res is non-null value. thats throw error

try to remove the ! mark.

if (res?.accessToken.isNotEmpty) {
  ... rest of your code

or add new contidion

if( res != null) {
  if (res!.accessToken.isNotEmpty){
  ... rest of your code
  }
}

hope it solve your issue. feel free to comment if any error occurred

CodePudding user response：

Try this code and test it.

Future<void> login(BuildContext context) async {
    if (loginFormKey.currentState?.validate() ?? false) {
      /*
      your API code
      */
      if (res.accessToken?.isNotEmpty ?? false) {
        /*
        if accessToken found
        */
      } else {
        /*
        if accessToken not found
        */
      }
    }
    return Future.value();
  }