listview、gradview滚动到最后时，滑动至顶部

mPhotoWall.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {

}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

if (firstVisibleItem==0){
//最顶部
}

if (firstVisibleItem+visibleItemCount>=totalItemCount){
//最底部
view.smoothScrollToPositionFromTop(0,0,2000);//2s内滑动到顶部
}
}
});