Android--判断listview上下滑动的方法

         elv_music_res_fragment.setOnScrollListener(new AbsListView.OnScrollListener() {
             private int mLastFirstPostion = 0;
             private int mLastFirstTop = 0;
             private int touchSlop = ViewConfiguration.get(getActivity()).getScaledTouchSlop();

             @Override
             public void onScrollStateChanged(AbsListView view, int scrollState) {

             }

             @Override
             public void onScroll(AbsListView absListView, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                 int currentTop;

                 View firstChildView = absListView.getChildAt(0);
                 if (firstChildView != null) {
                     currentTop = absListView.getChildAt(0).getTop();
                 } else {
                     //ListView初始化的时候会回调onScroll方法，此时getChildAt(0)仍是为空的
                     return;
                 }
                 //判断上次可见的第一个位置和这次可见的第一个位置
                 if (firstVisibleItem != mLastFirstPostion) {
                     //不是同一个位置
                     if (firstVisibleItem > mLastFirstPostion) {
                         // 下
                         if (rg_container_resFragment.getVisibility() != View.GONE) {
                             rg_container_resFragment.setVisibility(View.GONE);
                         }
                     } else {
                         // 上
                         if (rg_container_resFragment.getVisibility() != View.VISIBLE) {
                             rg_container_resFragment.setVisibility(View.VISIBLE);
                         }
                     }
                     mLastFirstTop = currentTop;
                 } else {
                     //是同一个位置
                     if (Math.abs(currentTop - mLastFirstTop) > touchSlop) {
                         //避免动作执行太频繁或误触，加入touchSlop判断，具体值可进行调整
                         if (currentTop > mLastFirstTop) {
                             // 上
                             if (rg_container_resFragment.getVisibility() != View.VISIBLE) {
                                 rg_container_resFragment.setVisibility(View.VISIBLE);
                             }
                         } else if (currentTop < mLastFirstTop) {
                             // 下
                             if (rg_container_resFragment.getVisibility() != View.GONE) {
                                 rg_container_resFragment.setVisibility(View.GONE);
                             }
                         }
                         mLastFirstTop = currentTop;
                     }
                 }
                 mLastFirstPostion = firstVisibleItem;
             }
         });