BaseAdapter problem

Hi all
I custom an adapter that extends BaseAdapter.In the getView() method I use the code Log.d("test",Integer.toString(position)); to output the position. The problem now is every time when the adapter notifyDataSetChanged() method is invoked the position first is 0 1 2 3 4(5 items in the screen) and then the displayed ListView item index in the screen.Why? Thank you very much!