Need an example about RecyclerView.Adapter.notifyItemChanged(int position, Object payload)

Question

According to RecyclerView documentation about medthod notifyItemChanged(int position, Object payload)

Notify any registered observers that the item at position has changed with an optional payload object.

I don't understand how to use second paramenter payload in this method. I have searched many document about "payload" but everything was ambiguous.

So, If you know about this method, please show me a clear example about it. Thank you very much.

Answer 1

If you want to update not all holder View but just part of it, this method is what you need.

Image that you have following ViewHolder

public class ViewHolder extends RecyclerView.ViewHolder {
        public final TextView tvPlayer;
        public final TextView tvScore;

        public ViewHolder(View view) {
            super(view);
            tvPlayer = (TextView) view.findViewById(R.id.tv_player);
            tvScore = (TextView) view.findViewById(R.id.tv_score);
        }

    }

And somewhere in your code you call adapter to update single TextView - tvScore

mRecyclerViewAdapter.notifyItemChanged(position, new Integer(4533));

[...]

onBindViewHolder(ViewHolder holder, int position, List payloads) catches callback at first. If payloads doesn't match your requirements you have to obligatory call super class super.onBindViewHolder(holder,position, payloads); which trigger onBindViewHolder(ViewHolder holder, int position) for other cases.

     // Update only part of ViewHolder that you are interested in
     // Invoked before onBindViewHolder(ViewHolder holder, int position)
        @Override
        public void onBindViewHolder(ViewHolder holder, int position, List<Object> payloads) {
            if(!payloads.isEmpty()) {
                if (payloads.get(0) instanceof Integer) {
                    holder.tvScore.setText(String.valueOf((Integer)payloads.get(0)))
                }
            }else {
                super.onBindViewHolder(holder,position, payloads);
            }
        }

    // Update ALL VIEW holder
    @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            MItem item = mList.get(position)
            // some update
        }