Android - ScrollView添加提示Arrow(箭头)

    private IScrollStateListener scrollStateListener;
    public void setScrollStateListener(IScrollStateListener listener) {
        scrollStateListener = listener;
    }

    public interface IScrollStateListener {
        void onScrollMostLeft();
        void onScrollFromMostLeft();
        void onScrollMostRight();
        void onScrollFromMostRight();
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);

        if (scrollStateListener != null) {
            if (l == 0) {
                scrollStateListener.onScrollMostLeft();
            } else if (oldl == 0) {
                scrollStateListener.onScrollFromMostLeft();
            }

            int mostRightL = this.getChildAt(0).getWidth()-getWidth();

            if (l >= mostRightL) {
                scrollStateListener.onScrollMostRight();
            } else if (oldl >= mostRightL && l < mostRightL) {
                scrollStateListener.onScrollFromMostRight();
            }
        }
    }

        final ImageView leftArrow = (ImageView)view.findViewById(R.id.doctor_gather_imageview_leftarrow);
        final ImageView rightArrow = (ImageView)view.findViewById(R.id.doctor_gather_imageview_rightarrow);

        AutoHorizontalScrollView scrollView = (AutoHorizontalScrollView)view.findViewById(R.id.doctor_gather_scrollview);
        scrollView.setScrollStateListener(new AutoHorizontalScrollView.IScrollStateListener() {
            @Override
            public void onScrollMostLeft() {
                Log.e(DEBUG + TAG, "滑动条最左面");
                leftArrow.setVisibility(View.INVISIBLE);
                rightArrow.setVisibility(View.VISIBLE);
            }

            @Override
            public void onScrollFromMostLeft() {
                Log.e(DEBUG+TAG, "滑动条离开最左面");
                leftArrow.setVisibility(View.VISIBLE);
                rightArrow.setVisibility(View.VISIBLE);
            }

            @Override
            public void onScrollMostRight() {
                Log.e(DEBUG+TAG, "滑动条最右面");
                leftArrow.setVisibility(View.VISIBLE);
                rightArrow.setVisibility(View.INVISIBLE);
            }

            @Override
            public void onScrollFromMostRight() {
                Log.e(DEBUG+TAG, "滑动条离开最右面");
                leftArrow.setVisibility(View.VISIBLE);
                rightArrow.setVisibility(View.VISIBLE);
            }
        });