Realtime database using firebase - retrieving a specific information

Question

So I am trying to create a real-time multiplayer quiz. I am using the Google Real-time Multiplayer API together with the firebase real-time database.

At the beginning of the game, users are prompted to ask themselves a question and provide two answers, where 1 answer is correct. Then this information is sent do Firebase Real-time Database under the child "Games" -- "mRoomId" --- "userId"

The variable uniqueRoomID is the specific id of the room which they players are retrieving from the Google API.

DatabaseReference myRef = database.getReference("Games").child(mRoomId).child(userId);

And I send 4 values with the setValue function to that specific reference.

Upload upload = new Upload(question,answer1,answer2, userId);

 myRef.setValue(upload);

My database tree is as follows

My Realtime Database Structure

My question is:

When I present a question to the other user later in the game, I don't want to show my own question, only the other user's question is relevant.

This is my valueEventListener:

 myReference = FirebaseDatabase.getInstance().getReference().child("Games").child(mRoomId);
  myReference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
      showData(dataSnapshot);
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {

    }
  });

And this is the method showData();

private void showData (DataSnapshot dataSnapshot){

for(DataSnapshot ds : dataSnapshot.getChildren()){

  Upload upload = ds.getValue(Upload.class);
  Log.d("TAG", "question1 is  " + upload.getQuestion1() );

}

}

The log in showData is returning two different questions from the database because it loops through the children.

How do I get only one of the questions that is relevant to be presented to the user playing the game ?

Should I structure this differently, or is there a way to get only the values that are relevant to me?

Which quiz question are you talking about (I can't see any node in your database named like that), how do you present a user the question. Please clear things out, the question is too ambiguous at the moment. — PradyumanDixit, Nov 19 '18 at 14:52

score 0 · Answer 1 · answered Nov 19 '18 at 15:39

There is no way to exclude a specific child node from a query. This means that (as far as I can see) you have two basic options:

Read both child nodes, and remove your own node client side based on the fact that its DataSnapshot.getKey() has the same value as User.getUid().
Read only the child node of the other player. This requires that you somehow already know the key/UID of the other player, but would allow you to then load only that player's data with DatabaseReference theirRef = database.getReference("Games").child(mRoomId).child(otherPlayerUid);

Also see:

1: In my case the getKey is actually returning the child "mRoomId" which is identical for user1 and user2. 2: I have tried to find a way to easily share this information between the two users (userId), but I have no luck at the moment. It will get more complex later in the development because it might include 3- or 4 users aswell.. — Guy Dude, Nov 20 '18 at 14:59

Realtime database using firebase - retrieving a specific information

1 Answers1