Adapter有关问题请问

public View getView(int position, View convertView, ViewGroup parent) {            ImageView i;            System.out.println(position+"  "+convertView);            if(convertView==null){            i = new ImageView(mContext);            i.setAdjustViewBounds(true);            i.setLayoutParams(new Gallery.LayoutParams(                    LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));            i.setBackgroundResource(R.drawable.picture_frame);            }            else i=(ImageView)convertView;            i.setImageResource(mThumbIds[position]);            return i;        }