回弹效果listview

public class ReboundListview extends ListView  
{  
    private static final int MAX_Y_OVERSCROLL_DISTANCE = 200;  

    private Context mContext;  
    private int mMaxYOverscrollDistance;  

    public BounceListView(Context context)   
    {  
        super(context);  
        mContext = context;  
        initBounceListView();  
    }  

    public BounceListView(Context context, AttributeSet attrs)   
    {  
        super(context, attrs);  
        mContext = context;  
        initBounceListView();  
    }  

    public BounceListView(Context context, AttributeSet attrs, int defStyle)   
    {  
        super(context, attrs, defStyle);  
        mContext = context;  
        initBounceListView();  
    }  

    private void initBounceListView()  
    {  
        //get the density of the screen and do some maths with it on the max overscroll distance  
        //variable so that you get similar behaviors no matter what the screen size  

        final DisplayMetrics metrics = mContext.getResources().getDisplayMetrics();  
            final float density = metrics.density;  

        mMaxYOverscrollDistance = (int) (density * MAX_Y_OVERSCROLL_DISTANCE);  
    }  

    @Override  
    protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent)   
    {   
        //This is where the magic happens, we have replaced the incoming maxOverScrollY with our own custom variable mMaxYOverscrollDistance;   
        return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, mMaxYOverscrollDistance, isTouchEvent);    
    }  

}