Retrieve all data under node in firebase realtime database

Question

I have a firebase realtime database and want to use the data to make a leaderboard. Im trying to retrieve all the data in my Scores node but am not sure how to loop through to g

Answer 1

It appears as though you are using a "Listener" class to access the data and print out the scores. The "ValueEventListener" listener you attached, with the "onDataChange()" method implemented, would not be called until there is a data change.

I'm not sure how you are using this class, but based on your question, I am assuming that you just want to print the scores when the "leaderboard.onCreate()" method is executed. Is this correct? If that is the case, you may not need to be attaching a listener.

Answer 2

You're going one level too deep into your JSON and are reading /Points/Points. Since that node doesn't exist, you get an empty snapshot in your onDataChange.

database.getReference().child("Scores").addValueEventListener(new ValueEventListener() {
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
            Log.i(TAG, "The scores are " + dataSnapshot.child("Points").getValue(Long.class));
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
    }
});

New Code that returns values:

public class leaderboard extends AppCompatActivity {

    DatabaseReference databaseUsers;
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    FirebaseAuth mAuth;
    TextView score;
    private static final String TAG = "leaderboard";



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

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser user = mAuth.getCurrentUser();
        score = (TextView) findViewById(R.id.tableText);


        database.getReference().child("Scores").addValueEventListener(new ValueEventListener() {
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        System.out.println("The score is: " + snapshot.toString());
                        score.setText(snapshot.toString());
                    }
                }


            @Override
            public void onCancelled(DatabaseError databaseError) {
             // Getting Post failed, log a message
             Log.w(TAG, "loadPost:onCancelled", databaseError.toException());

    }


});

        }
}

This is my progress: