onDataChange's value returns null

Question

I'm trying to get data from my Firebase database I have two Fragments, one for signing up and the other for signing in I have no problems with inserting data into the Firebase, but somehow i'm unable to return the data from it

These are some codes from my sign in Fragment:

private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;

 @Override
    public void onStart() {
        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
            mAuth.removeAuthStateListener(mAuthListener);
        }
    }

I have this code inside onCreate method:

 mAuth = FirebaseAuth.getInstance();
        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                user = firebaseAuth.getCurrentUser();
                if(user != null)
                {
                    getExistingUserInfo(user.getUid());
            }
        };

This is the method where i query the data from my firebase

 public void getExistingUserInfo(String uid){

        final FirebaseDatabase database = FirebaseDatabase.getInstance();

        database.getReference("allUsers").child(uid)
                .orderByChild("emailAddress")
                .equalTo(mEmailStr)
                .addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        Log.e("Data Changed YEA!",dataSnapshot.toString());

                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                    }

                });

The problem is, when i launch the Application and getExistingUserInfo gets called inside onCreate, it returns the data of the last signed in user from my device correctly

> E/Data Changed YEA!: DataSnapshot { key =
> vWOypZ07sbeQKEtXnAwbEEV7ml43, value = {password=123456789,
> username=ahmed, sgl=true, emailAddress=ahmeddirect@gmail.com,
> studyGroupName=Study Group 2} }

But when I press sign in, it value returns null

E/Data Changed YEA!: DataSnapshot { key = vWOypZ07sbeQKEtXnAwbEEV7ml43, value = null }

So I have to close the application and reopen it in order to get the data correctly!!

The is the code where the user gets signed in, it's inside a clickListener in onCreateView method:

mAuth.signInWithEmailAndPassword(mEmailStr, mPasswordStr).addOnCompleteListener(getActivity(), new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(Task<AuthResult> task) {
                        if (task.isSuccessful())
{

 Toast.makeText(getContext(),"Succeed!",Toast.LENGTH_LONG).show();

                            }
                            else
                            {
                                Toast.makeText(getContext(),"Failed!",Toast.LENGTH_LONG).show();
                            }
                    }
                });

And this is how my database looks like:

Click to see the Image

Answer 1

Alright, first of all i don't see why you're using AuthStateListener Remove the code inside onStart, onStop and onCreate Replace your getExistingUserInfo with this

public void getExistingUserInfo() {
    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    String userID = user.getUid();
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    database.getReference("allUsers").child(userID).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            hashMap = (HashMap<String, String>) dataSnapshot.getValue();
            List<String> dataS = new ArrayList<>(hashMap.values());

            for (String data : dataS) {
                Log.e("Database Data", data);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

Post this method inside the onClickListener of the signin button and that should be it

Note: If you wanna do anything with the returned data then you should do it inside onDataChange after the data is returned