Multiple Query and Ref Firebase Database Android

user_10462948 0
Viewed 3443

My firebase database looks like this:

database

From this query

String currentUserID = FirebaseAuth
                            .getInstace()
                            .getCurrentUser()
                            .getUid();

DatabaseReference favorsRef = FirebaseDatabase
                                        .getInstance()
                                        .getReference()
                                        .child("favors");
Query myChatsQuery = favorsRef
                        .orderByChild("uid")
                        .equalTo(currentUserID);

I need to create other query to get just the tuples from myChatsQuery who has the child called "messages". If the tuple doesn't have the child "messages", I don't want to insert it in my new query.

So, How I can create a query from other query?

Help me please,

Thanks in advance.

firebase-realtime-database firebase android java
2 Answers

Unfortunately, orderByChild() does not work on multiple same fields at once, so you may have to do the job in two steps.

First you can run an orderByChild() query looking for the currentUserId and then add all those that match to an ArrayList and then run orderByChild() in those found uids for messages.

This looks something like this, in code:

reference.orderByChild("uid").equalTo(currentUserId).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            if(dataSnapshot.exists())
                              array.add(dataSnapshot.getValue(String.class);
                        }

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

                        }
                  )};

This code above adds uids matching currentUserId to the ArrayList array.

databaseReference.child(array.get(0)).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                           if(dataSnapshot.child("messages").exists())
                           // do your thing

                        }

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

                        }

                    )};

You can also just use a for loop to go through all the values in the array.

user_88508750

To solve this, please use the following code:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef.child("favors").orderByChild("uid").equalTo(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            if(ds.child("messages").exists()) {
                //Do what you need to do
            }
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage());
    }
};
query.addListenerForSingleValueEvent(valueEventListener);

As you can see, you can solve this by querying the database only once.

user_52468850
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