android 的ListView中，如何判断其内容已滚动到最顶部、底部

listView.setOnScrollListener(new OnScrollListener() {            @Override            public void onScrollStateChanged(AbsListView view, int scrollState) {            }            @Override            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {                if(firstVisibleItem==0){                    Log.e("log", "滑到顶部");                }                if(visibleItemCount+firstVisibleItem==totalItemCount){                    Log.e("log", "滑到底部");                }            }        });