NullPointerException while retrieving data from Firebase

Question

I'm trying to set my TextView to the current user username but i'm getting this error:

 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference

and this is how i'm retrieving the username:

mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

               String name= dataSnapshot.child("username").getValue().toString();
               username.setText(name);

           }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.w("ProfileActivity", "load:onCancelled", databaseError.toException());

        }
    });

this is my user node:

this:

 mCurrUser = FirebaseAuth.getInstance().getCurrentUser();
 Uid = mCurrUser.getUid();
 mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(Uid);

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — itwasntme, Feb 27 '20 at 20:21
Why are you calling `toString()` in the first place? It's already a string. If you weren't doing that yuo wouldn't have got this NPE, you would just have called `username.setText(null)`. — user207421, Feb 27 '20 at 22:38

Doug Stevenson · Accepted Answer · 2020-02-27T21:18:43.067

0

dataSnapshot.child("username").getValue() is returning null, which means that there is no child called "username" at the location of your query. From your comments, it sounds like you're building mDatabase like this:

mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(Uid);

The problem here is that your code is accessing "Users" with a capital U, but the data you're showing in the database exists at "users" with a lowercase u.

edited Feb 27 '20 at 21:18

answered Feb 27 '20 at 20:33

Doug Stevenson

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`mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(Uid);` – Afaf Matg Feb 27 '20 at 20:39
`Uid` is probably not what you expect. – Doug Stevenson Feb 27 '20 at 20:44
what do you mean? – Afaf Matg Feb 27 '20 at 20:49
What exactly is `Uid`? Log its value. Does it have the value you expect for the query? – Doug Stevenson Feb 27 '20 at 21:01
yeah it's 9ebbbm1B9gY21JHSucA9iCFDAw73 and i'm logged as 'admin' which matches the uid – Afaf Matg Feb 27 '20 at 21:08
You should be accessing "users" with a lowercase u, instead of "Users" with a capital U. – Doug Stevenson Feb 27 '20 at 21:19
yeah you're right ! thank you so much !!!! – Afaf Matg Feb 27 '20 at 21:26

NullPointerException while retrieving data from Firebase

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