RecyclerView updates only on scroll

Question

I have a layout with a RecyclerView with the adapter:

public class SimpleRecyclerAdapter extends RecyclerView.Adapter<SimpleViewHolder> {

  protected List<JSONObject> data = new ArrayList<>();

  public List<JSONObject> getData() { return data; }
}     

I update it's adapter like:

public void udpdateFromJson( JSONObject payload ) {
  JSONArray msgs = payload.optJSONArray( "messages" );
  for( int ix = 0; null != msgs && ix < msgs.length(); ix++ ){
    JSONObject o = msgs.optJSONObject( ix );
    if( loadingMore ) adapter.getData().add( 1 + ix, o );
    else adapter.getData().add( o );
  }

  adapter.notifyDataSetChanged();
  recyclerView.invalidate();
}

The problem is, that I get to see the new item only when I touch or scroll the view.

What am I missing?

UPDATE:

to fix the problem I replaced the lines

adapter.notifyDataSetChanged();
recyclerView.invalidate();

with

adapter.notifyItemRangeInserted( loadingMore ? 1 : 0, msgs.length() );

and it worked

Answer 1

try specifying the position of the item inserted or removed instead of notifyDataSetChanged();. you can use

notifyItemInserted(int pos);
notifyItemRangeChanged(int start, int end);`

Answer 2

Most likely you are calling notifyDataSetChanged from background thread.

Simply (and ugly) fix you can do is to use:

recyclerView.post(new Runnable(){ @Override public void run(){ adapter.notifyDataSetChanged(); } });

If notifyDataSetChanged is called correctly from main thread then the list is updated without touching it.