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;
            }
        });