获取最大 Horizo​​ntalScrollView 滚动量

Question

我正在向我的HorizontalScrollView 添加浮动箭头，这将让用户知道当前视图之外还有更多项目。

我需要的是如何判断视图是否已滚动到最大值。你会认为getMaxScrollAmount() 方法会给你这个 - 它没有，在我的代码中它给了我视图的宽度。去弄清楚为什么。这是我的代码 - 又好又简单：

    final ImageView leftArrow = (ImageView) toReturn.findViewById(R.id.leftArrow);
    final ImageView rightArrow = (ImageView) toReturn.findViewById(R.id.rightArrow);

    final HorizontalScrollView scrollView = (HorizontalScrollView) toReturn.findViewById(R.id.actionBarHoriztonalScroll);


    final GestureDetector gd = new GestureDetector(new SimpleOnGestureListener() {
        @Override
        public boolean onScroll(MotionEvent e1, 
                                MotionEvent e2, 
                                float distanceX, 
                                float distanceY) {
            if(scrollView.getScrollX() == 0) {
                leftArrow.setVisibility(View.GONE);
            } else {
                leftArrow.setVisibility(View.VISIBLE);
            }
            if(scrollView.getScrollX() == scrollView.getMaxScrollAmount() ||
                scrollView.getMaxScrollAmount() == 0) {
                rightArrow.setVisibility(View.GONE);
            } else {
                rightArrow.setVisibility(View.VISIBLE);
            }

            Log.v(ClientDetailsFragment.class.getSimpleName(), "max: " + scrollView.getMaxScrollAmount() +
                                                            "current: " + scrollView.getScrollX());
            return super.onScroll(e1, e2, distanceX, distanceY);
        }
    });

    scrollView.setOnTouchListener(new OnTouchListener() {

        @Override
        public boolean onTouch(View arg0, MotionEvent ev) {
            gd.onTouchEvent(ev);
            return false;
        }
    });

上述调试的输出：

10-03 14:36:16.343: VERBOSE/(20508): max: 240 current: 126
10-03 14:36:16.363: VERBOSE/(20508): max: 240 current: 127
10-03 14:36:16.386: VERBOSE/(20508): max: 240 current: 132
10-03 14:36:16.398: VERBOSE/(20508): max: 240 current: 143
10-03 14:36:16.417: VERBOSE/(20508): max: 240 current: 149
10-03 14:36:16.433: VERBOSE/(20508): max: 240 current: 152
10-03 14:36:16.449: VERBOSE/(20508): max: 240 current: 152
10-03 14:36:16.468: VERBOSE/(20508): max: 240 current: 152

（在这种情况下，152 是最大值）

Answer 1

水平滚动视图的子视图应该有正确的宽度。试试这个

Log.e("ScrollWidth",Integer.toString(horizontalScrollview.getChildAt(0).getMeasuredWidth()-
        getWindowManager().getDefaultDisplay().getWidth()));

这应该是最大滚动量。

将以下代码放入您的 onCreate 方法中

ViewTreeObserver vto = scrollView.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
        scrollView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
        Log.e("ScrollWidth",Integer.toString(horizontalScrollview.getChildAt(0)
                .getMeasuredWidth()-getWindowManager().getDefaultDisplay().getWidth()));

    }
});