Recyclerview scroll position with Firebase

Question

I am listing data from Firebase in a RecyclerView, but when adding or removing data, the data is repeated in the list. I used the clear(); or lista.removeAll(lista); to clear before filling only the list is updated and back scroll position to start. Does anyone have an idea how to avoid this? Just follow my code:

ValueEventListener listener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        //
        Escala.removeAll(Escala);
        for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()){

            ModelEscala model = singleSnapshot.getValue(ModelEscala.class);
            Escala.add(model);
            recyclerViewAdapterEscalas = new RecyclerViewAdapterEscalas(getActivity(), Escala, mImageLoader);
            recyclerViewAdapterEscalas.notifyDataSetChanged();

            recyclerView.setAdapter(recyclerViewAdapterEscalas);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
};

mDataBase.addValueEventListener(listener);

Answer 1

The problem is being in the method recyclerView.setAdapter(recyclerViewAdapterEscalas); the ideal would be to instantiate the Adapter and assign to the recyclerView only 1 time, to update the data you just need to manipulate your Arraylist and notify the Adapter (recyclerViewAdapterEscalas.notifyDataSetChanged();)

Example:

recyclerViewAdapterEscalas = new RecyclerViewAdapterEscalas(getActivity(), Escala, mImageLoader);
recyclerView.setAdapter(recyclerViewAdapterEscalas);

ValueEventListener listener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {       
        Escala.removeAll(Escala);
        for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()){

            ModelEscala model = singleSnapshot.getValue(ModelEscala.class);
            Escala.add(model);
            recyclerViewAdapterEscalas.notifyDataSetChanged();            
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
};

mDataBase.addValueEventListener(listener);

Try this way, I hope I’ve helped.