How to get sorted data based on timestamp from firebase

Question

I am developing an android chat application in which I need to order the conversation details by the timestamp. My firebase data structure is mentioned below .

storing data like this

Now I want to retrieve and show the data in decending/latest order on my RecyclerView from firebase realtime database based on timestamp.

I have tried the following approaches.

 final DatabaseReference nm= FirebaseDatabase.getInstance().getReference("Transaction");

            Query query = nm.orderByChild("Timestamp")
                            .limitToLast(5);


    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            listData.clear();
            if (dataSnapshot.exists()){
                for (DataSnapshot npsnapshot : dataSnapshot.getChildren()){
                    Transaction ld=  npsnapshot.getValue(Transaction.class);

                    listData.add(ld);
                }
                Tadapter=new TransactionAdapter(listData);
                rv.setAdapter(Tadapter);
                Log.d(TAG,"Total Count"+Tadapter.getItemCount());

            }
        }

Your code seems to okay bro , whats the problem you faced? – Zahid Islam Jul 30 '21 at 17:14 — Zahid Islam, Jul 30 '21 at 17:14

score 0 · Accepted Answer · answered Jul 30 '21 at 16:12

I think you are doing minor mistake in this code

query.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        listData.clear();
        if (dataSnapshot.exists()){
            for (DataSnapshot npsnapshot : dataSnapshot.getChildren()){
                Transaction ld=  npsnapshot.getValue(Transaction.class);

                listData.add(ld);
            }
            Tadapter=new TransactionAdapter(listData);
            rv.setAdapter(Tadapter);
            Log.d(TAG,"Total Count"+Tadapter.getItemCount());

        }
    }

You are doing a query to singleEvent you have to do a query for addValueEventListener

query.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            listData.clear();
            if (dataSnapshot.exists()){
                for (DataSnapshot npsnapshot : dataSnapshot.getChildren()){
                    Transaction ld=  npsnapshot.getValue(Transaction.class);

                    listData.add(ld);
                }
                Tadapter=new TransactionAdapter(listData);
                rv.setAdapter(Tadapter);
                Log.d(TAG,"Total Count"+Tadapter.getItemCount());
            }
        }

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

        }
    });

How to get sorted data based on timestamp from firebase

1 Answers1