CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-databaseandroid-recyclerview
Tamim Attafi
Tamim Attafi

Reputation: 2511

FirebaseDatabase Query : How to query some data basing on some values from other childs. For FirebaseRecyclerAdapter

I'm working on my app that has a fragment, this fragment displays new users with a follow button using this query :

query = mDatabaseref.child("users").orderByChild("date").limitToLast(10);

After a follow button is clicked, the current User Uid gets saved as a child in the other child that has a name "Follows" with 2 other child's "following" and "followers" as it showed in the below picture :

enter image description here

what I want to do is to make a Query for an other fragment with the name Following and show all the users that the Current user is following with the ability of getting their names, I was thinking of making a data dataSnapshot in the FirebaseRecyclerAdapter onBindViewHolder method basing on the Uid tooken from the childs, but I think it's gonna be complex, on the other hand, i tried to sort the follows in the user Info child direclty, but it leads to a strange behaviour on the RecyclerView.

Upvotes: 0

Views: 56

Answers (1)

Alex Mamo
Alex Mamo

Reputation: 138824

I'm not going to write you all the code including your FirebaseRecyclerAdapter, I will show you just how to query to get the desired results. As i understand, here is the problem. So in order to achieve this, you need to query your database twice, once to get all those ids and second, based on those ids to get the names. So, please use the following code:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference followingRef = rootRef.child("follows").child(uid).child("following");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String userId = ds.getKey();

            DatabaseReference userIdRef = rootRef.child("users").child(userId);
            ValueEventListener eventListener = new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
                        String name = dSnapshot.child("name").getValue(String.class);
                        Log.d("TAG", name);
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {}
            };
            userIdRef.addListenerForSingleValueEvent(eventListener);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
followingRef.addListenerForSingleValueEvent(valueEventListener);

The result in your logcat will be all the names of the followers that belong to a single user.

Upvotes: 2

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