public void addFooterHolder(ViewHolder viewHolder){
  tryThrowAlreadyBoundException("Cannot bind a footer holder post-bind due to limitations of view types and recycling.");
  footerHolders.add(viewHolder);
  onItemRangeInserted(getFooterStartIndex() + getFootersCount(),1);
}

public void addFooterHolder ( ViewHolder viewHolder ) { tryThrowAlreadyBoundException ( "Cannot bind a footer holder post-bind due to limitations of view types and recycling." ) ; footerHolders . add ( viewHolder ) ; onItemRangeInserted ( getFooterStartIndex ( ) + getFootersCount ( ) , 1 ) ; }
adds a footer to this adapter .
