question: public void addFooter ( Object footer ) { if ( mMode != YfListMode . MODE_DATA ) { Log . e ( TAG , "error: you can not add header or footer while you are not in data mode" ) ; return ; } if ( ! mFooters . contains ( footer ) ) { mFooters . add ( footer ) ; notifyItemInserted ( mHeaders . size ( ) + mData . size ( ) + mFooters . size ( ) - 1 ) ; } }
target:  add a footer to the adapter