Login activity in Firebase authentication is not launching from a new activity

Question

I am using a new activity to launch the Firebase authentication Activity and post the authenticated user in my NodeJS API but the Firebase authentication activity is not launching even when i have not authenticated.

Here is the code:

    public class loginActivity extends AppCompatActivity {
        FirebaseAuth auth;
        private static final int RC_SIGN_IN=1;
        double latitude,longitude;
        boolean isAuthDone=false;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_login);
            auth=FirebaseAuth.getInstance();
            if(auth.getCurrentUser() != null){
                //user already logged in
                Log.d("TAG     ", auth.getCurrentUser().getEmail()+" already logged in.");
                onBackPressed();
            }
            else {

                    loginFunction();

            }

            String name=auth.getCurrentUser().getDisplayName(); //LINE 54
            String email=auth.getCurrentUser().getEmail();

            // POST TO API
            GPSTracker tracker = new GPSTracker(this);
            if (!tracker.canGetLocation()) {
                tracker.showSettingsAlert();
            } else {
                latitude = tracker.getLatitude();
                longitude = tracker.getLongitude(); //LOCATION
            }


            String loc = latitude+", "+longitude;
            Users newUser=new Users(name, email, loc, "0", false);

    //        if(!isAuthDone){
    //            while(!isAuthDone){
    //                loginFunction();    //ASK FOR LOGIN UNTIL THE USER AUTHENTICATES.
    //            }
    //        }

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(ApiUrls.BASEURL)
                    .addConverterFactory(GsonConverterFactory.create(new GsonBuilder().serializeNulls().create()))
                    .build();
            ApiInterface apiI;
            apiI= retrofit.create(ApiInterface.class);
            Call call;
            call=apiI.saveUser(newUser);
            call.enqueue(new Callback() {
                @Override
                public void onResponse(Call call, Response response) {
                    if(response.isSuccessful()){
                        Log.e("User reg. in API",response.message()+response.code());
                        Users user=response.body();
                        ApiUrls.userName=auth.getCurrentUser().getDisplayName();
                        ApiUrls.userID=user.getID()+"";     //THIS IS VERY IMPORTANT.
                        ApiUrls.userEmail=user.getEmail();
                        ApiUrls.profilePicURL=auth.getCurrentUser().getPhotoUrl();
                        ApiUrls.isUserLoggedInAndSaved=true;
                    }
                }
                @Override
                public void onFailure(Call call, Throwable t) {
                    Log.e("TAG", "Not posted in API");
                    AuthUI.getInstance()
                            .signOut(loginActivity.this)
                            .addOnCompleteListener(new OnCompleteListener() {
                                @Override
                                public void onComplete(Task task) {
                                    Log.d("TAG    ", "Signed out from this app.");
                                    onBackPressed();
                                }
                            });
                    ApiUrls.isUserLoggedInAndSaved=false;
                    //Sign out from the email and launch a DIALOG to try again.
                }
            });
            onBackPressed();

        }

        private void loginFunction() {
                startActivityForResult(AuthUI.getInstance()
                        .createSignInIntentBuilder()
                        .setProviders(AuthUI.FACEBOOK_PROVIDER,
                                AuthUI.EMAIL_PROVIDER,
                                AuthUI.GOOGLE_PROVIDER).build(),RC_SIGN_IN);

        }

        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);
            if(requestCode == RC_SIGN_IN){
                if(resultCode == RESULT_OK){
                    Log.d("TAG logged in", auth.getCurrentUser().getEmail());
                    isAuthDone=true;
                }
                else{
                    Log.d("TAG    ", "USER NOT AUTHENTICATED");
                    //Launch a dialog to turn the internet ON and redirect to some other activity.
                }
            }
        }
    }

Earlier i was launching the Firebase authentication Activity from many places. There it worked but now it is not working. Error is:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getDisplayName()' on a null object reference at com.example.aavgeensingh.shuddhi.Activities.loginActivity.onCreate(loginActivity.java:54)

Edit: I know the cause now. But is there any way i can wait for the user to authenticate first and then post the details to my API using retrofit.

Answer 1

After you call loginFunction() the rest of the onCreate() function continues to execute so the user can be null. You should end execution before this point.