我想，当到达终点，右边的按钮会改变颜色，在到达的开始，左键会变色，所以，我想问问如何检测到Horizo​​ntalScrollView已经到头了。

  maxScrollX = horizo​​ntalScrollView.getChildAt（0）.getMeasuredWidth（） -  horizo​​ntalScrollView.getMeasuredWidth（）;    如果（horizo​​ntalScrollView.getScrollX（）== 0）{        lImageView.setImageResource（R.drawable.left_green）;    }其他{        lImageView.setImageResource（R.drawable.left）;    }    如果（horizo​​ntalScrollView.getScrollX（）== maxScrollX）{        rImageView.setImageResource（R.drawable.right_green）;    }其他{        rImageView.setImageResource（R.drawable.right）;    } 

i want when reach to end ,the right button will change color ,when reach to the begin,the left button will change color ,so ,i want to ask how to detect that the HorizontalScrollView has reached an end.

    maxScrollX = horizontalScrollView.getChildAt(0).getMeasuredWidth()-horizontalScrollView.getMeasuredWidth(); 
    if (horizontalScrollView.getScrollX() == 0) { 
        lImageView.setImageResource(R.drawable.left_green); 
    } else { 
        lImageView.setImageResource(R.drawable.left); 
    }

    if (horizontalScrollView.getScrollX() == maxScrollX) { 
        rImageView.setImageResource(R.drawable.right_green); 
    } else { 
        rImageView.setImageResource(R.drawable.right); 
    }