Flutter, How to use multiple shared preferences-CodePudding

My goal was to avoid users getting logged out once they close and reopened the app. So, I used shared_preferences to store the user's email and password locally so, that whenever the user reopens the app I could use firebase's signInWithEmailAndPassword and provide locally stored email and password to it. I used setString() to store email password but I was able to store only email and not the password, I get the error "Password is null" How do I solve this. Did I do the code right?

Storing email and password when user registers in app

onPressed: () async {
                  try {
                    final user =
                        await _auth.createUserWithEmailAndPassword(
                            email: email, password: password);
                    if (user != null) {
                      final SharedPreferences sharedPreferences =
                          await SharedPreferences.getInstance();
                      sharedPreferences.setString(
                        'email',
                        email,
                      );
                      sharedPreferences.setString('password', password);
                      Get.to(() => const BorrowerList());
                    }
                  } catch (e) {
                    Get.snackbar('Error', e.toString(),
                        backgroundColor: (Colors.red));
                  }
                },

fetching email password and login after reopening.

  @override
  void initState() {
    super.initState();
    validateUserAuth();
  }

  final _firestore = FirebaseFirestore.instance;
  void validateUserAuth() async {
    final SharedPreferences sharedPreferences =
        await SharedPreferences.getInstance();
    var obtainedEmail = sharedPreferences.getString('email');
    var obtainedPassword = sharedPreferences.getString('password');
    if (obtainedEmail != null || obtainedPassword != null) {
      setState(() {
        loggedinUserEmail = obtainedEmail!;
        loggedinUserPassword = obtainedPassword!;
      });
      if (loggedinUserEmail != null || loggedinUserPassword != null) {
        final loggedinuser = await auth.signInWithEmailAndPassword(
            email: loggedinUserEmail, password: obtainedPassword!);
        if (loggedinuser != null) {
          Get.to(() => const BorrowerList());
        }
      }
    } else {
      Get.to(() => AuthScreen());
    }
  }

CodePudding user response：

The error is apparent. You can't save a null value in shared_preferences.

Your code is not complete. somehow your password variable is null.

You can paste complete code so we can help you better

CodePudding user response：

Can you provide more information about the project? So far, it's obvious that you're trying to store a null value in shared_preferences. You can't do that. I'm pretty sure the problem is that when the user enters a password, it's not stored in the password variable here:

                  try {
                    final user =
                        await _auth.createUserWithEmailAndPassword(
                            email: email, password: password);
                    if (user != null) {
                      final SharedPreferences sharedPreferences =
                          await SharedPreferences.getInstance();
                      sharedPreferences.setString(
                        'email',
                        email,
                      );
                      // NULLABLE VARIABLE!
                      sharedPreferences.setString('password', password);
                      Get.to(() => const BorrowerList());
                    }
                  } catch (e) {
                    Get.snackbar('Error', e.toString(),
                        backgroundColor: (Colors.red));
                  }
                },

Additionally, it is not recommended to use shared_preferences for storing sensitive data. Flutter Secure Storage is much better suited for this.