Event Listener for single event calling same value multiple times

Question

I am using reference of one node to get data from another node in Firebase Realtime Database.What i am doing is first getting the size of users under current user Uid in chatlist node then calling those userids from users node and printing them on to my recyclerview.What error i am getting is even though i get the size correct but userids add multiple times.

Database Structure

Logcat

2020-04-19 14:25:31.411 12076-12076/com.shivam.chatapp2 D/Tag2: Size for each  loop   1
2020-04-19 14:25:31.411 12076-12076/com.shivam.chatapp2 D/Tag2: Size for each  loop   2
2020-04-19 14:25:31.412 12076-12076/com.shivam.chatapp2 D/Tag2: User List Ids :  KRhmaWXCctMHbU1Z6NAWRGGw2ag2
2020-04-19 14:25:31.417 12076-12076/com.shivam.chatapp2 D/Tag2: User List Ids :  n9KF5J5wuzSj4npgO8p16b7cOIV2
2020-04-19 14:25:31.419 12076-12076/com.shivam.chatapp2 D/Tag2: User List Ids :  KRhmaWXCctMHbU1Z6NAWRGGw2ag2
2020-04-19 14:25:31.422 12076-12076/com.shivam.chatapp2 D/Tag2: User List Ids :  n9KF5J5wuzSj4npgO8p16b7cOIV2
2020-04-19 14:25:31.678 12076-12076/com.shivam.chatapp2 D/Tag2: Name called  Shivam
2020-04-19 14:25:31.683 12076-12076/com.shivam.chatapp2 D/Tag2: Name called  Shivam
2020-04-19 14:25:31.694 12076-12076/com.shivam.chatapp2 D/Tag2: Name called  Harshita
2020-04-19 14:25:31.695 12076-12076/com.shivam.chatapp2 D/Tag2: Name called  Harshita

Code

 private void chatlist_loop(){
    mUsers.clear();

    mUserAdapter = new UserAdapter(getContext(), mUsers, false);
    recyclerView.setAdapter(mUserAdapter);
    mUserAdapter.notifyDataSetChanged();

    String fuser;
    fuser = FirebaseAuth.getInstance().getCurrentUser().getUid();
    rootRef = FirebaseDatabase.getInstance().getReference();
    ChatlistRef = rootRef.child("Chatlist").child(fuser);

    mValueEventListener=new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            for (DataSnapshot ds : dataSnapshot.getChildren()) {
                String userIDS = ds.getKey();

                UserChatList.add(userIDS);
                Log.d(TAG,"Size for each  loop   "+UserChatList.size());
            }

            UserListSize=UserChatList.size();
            for (int i =1;i<=UserListSize;i++) {
                for (String usereReference:UserChatList) {
                    Log.d(TAG,"User List Ids :  " +usereReference);
                    DatabaseReference UserRef= FirebaseDatabase.getInstance().getReference("Users").child(usereReference);

                    ValueEventListener eventListener = new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            User user = dataSnapshot.getValue(User.class);
                            mUsers.add(user);
                            mUserAdapter.notifyDataSetChanged();
                            String name = dataSnapshot.child("First").getValue(String.class);
                            Log.d(TAG, "Name called  "+name);

                        }

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

                        }
                    };
                    UserRef.addListenerForSingleValueEvent(eventListener);

                }
            }

        }

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

        }
    };
    ChatlistRef.addListenerForSingleValueEvent(mValueEventListener);

Answer 1

You are making a for each loop for every iteration of the regular for loop, this is why you get multiple values added, try this:

...........
...........

mValueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {

//loop through every user id in the fuser node      
for (DataSnapshot ds : dataSnapshot.getChildren()) {

//grab the id
String userID = ds.getKey();

//start a new call to users to grab details
DatabaseReference UserRef= FirebaseDatabase.getInstance().getReference("Users").child(userID);


UserRef.addListenerForSingleValueEvent(new ValueEventListener() {

@Override
public void onDataChange(DataSnapshot dataSnapshot) {

//fill the list with the needed users  
User user = dataSnapshot.getValue(User.class); 
mUsers.add(user);
mUserAdapter.notifyDataSetChanged();


}

@Override
public void onCancelled(DatabaseError databaseError) {

Log.w(TAG, "loadPost:onCancelled", databaseError.toException());

}



});



}

//finish loop


}

@Override
public void onCancelled(DatabaseError databaseError) {

Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
        // ...
}
};
ChatlistRef.addValueEventListener(mValueEventListener);