监听HorizontalScrollView滑动到最左/最右

监听ScrollView滑动停止后，滚动条的位置，是在最左?最右?其它地方?

1，先定制HorizontalScrollView

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.widget.HorizontalScrollView;

public class ScrollViewCustom extends HorizontalScrollView
{
    private Runnable scrollerTask;
    private int intitPosition;
    private int newCheck = 100;
    private int childWidth = 0;

    public interface OnScrollStopListner
    {
        /**
         * scroll have stoped
         */
        void onScrollStoped();
        /**
         * scroll have stoped, and is at left edge
         */
        void onScrollToLeftEdge();
        /**
         * scroll have stoped, and is at right edge
         */
        void onScrollToRightEdge();
        /**
         * scroll have stoped, and is at middle
         */
        void onScrollToMiddle();
    }

    private OnScrollStopListner onScrollstopListner;

    public ScrollViewCustom(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        scrollerTask = new Runnable()
        {
            @Override
            public void run()
            {
                int newPosition = getScrollX();
                if (intitPosition - newPosition == 0)
                {
                    if(onScrollstopListner == null)
                    {
                        return;
                    }
                    onScrollstopListner.onScrollStoped();
                    Rect outRect = new Rect();
                    getDrawingRect(outRect);
                    if(getScrollX() == 0)
                    {
                        onScrollstopListner.onScrollToLeftEdge();
                    }
                    else if(childWidth + getPaddingLeft() + getPaddingRight() == outRect.right)
                    {
                        onScrollstopListner.onScrollToRightEdge();
                    }
                    else
                    {
                        onScrollstopListner.onScrollToMiddle();
                    }
                } else
                {
                    intitPosition = getScrollX();
                    postDelayed(scrollerTask, newCheck);
                }
            }
        };
    }
    

    public void setOnScrollStopListner(OnScrollStopListner listner)
    {
        onScrollstopListner = listner;
    }

    public void startScrollerTask()
    {
        intitPosition = getScrollX();
        postDelayed(scrollerTask, newCheck);
        checkTotalWidth();
    }
    private void checkTotalWidth()
    {
        if(childWidth > 0)
        {
            return;
        }
        for(int i = 0; i < getChildCount(); i++)
        {
            childWidth += getChildAt(i).getWidth();
        }
    }

} 

2，使用

    protected void onCreate(Bundle savedInstanceState)
    {
        final ScrollViewCustom scrollView;
        scrollView.setOnTouchListener(new OnTouchListener()
        {
            public boolean onTouch(View v, MotionEvent event)
            {
                if (event.getAction() == MotionEvent.ACTION_UP)
                {
                    scrollView.startScrollerTask();
                }
                return false;
            }
        });
        scrollView.setOnScrollStopListner(new OnScrollStopListner()
        {
            public void onScrollToRightEdge()
            {
            }
            public void onScrollToMiddle()
            {
            }
            public void onScrollToLeftEdge()
            {
            }
            public void onScrollStoped()
            {
            }
        });

    }