Getting blank screen when using get Method to fetch the username

Question

HelloActivity.java

public class HelloActivity extends BaseActivity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hello);

        final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        DatabaseReference database = FirebaseDatabase.getInstance().getReference("users");
        database = database.child(user.getUid());

        database.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                hideProgress();
        UserModel userModel = dataSnapshot.getValue(UserModel.class);
        ((TextView) findViewById(R.id.textView)).setText("Hello " + userModel.getFirst_name() + " " + userModel.getLast_name());
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
                hideProgress();
                Log.d("==>", "==>" + databaseError);
            }
        });

    }
}

So the problem is that this Hello activity opens after I log into my app but I get a blank screen in there rather than "Hello firstname lastname" of the user.