ScrollView拖動回彈效果

原理

在android2.3版本中，View類中新增了一個方法：overScrollBy。通過覆蓋該方法，就可以達到阻尼回彈的效果。

示例1、豎向滾動

public class ReboundScrollView extends ScrollView{
	private static final int MAX_SCROLL = 200;
	private static final float SCROLL_RATIO = 0.5f;// 阻尼係數 
	
	public ReboundScrollView(Context context)
	{
		super(context);
	}

	public ReboundScrollView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
	}

	public ReboundScrollView(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
	}
	
	@Override  
	protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent)
	{   
    	int newDeltaY = deltaY;
    	int delta = (int) (deltaY * SCROLL_RATIO);
		if((scrollY+deltaY)==0 || (scrollY-scrollRangeY+deltaY)==0){ 
			newDeltaY = deltaY;		//回彈最後一次滾動，復位
		}else{
			newDeltaY = delta;		//增加阻尼效果
		}
        return super.overScrollBy(deltaX, newDeltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, MAX_SCROLL, isTouchEvent);    
    }
	
	

}

示例2、橫向滾動

public class ReboundHScrollView extends HorizontalScrollView{
	private static final int MAX_SCROLL = 200;
	private static final float SCROLL_RATIO = 0.5f;// 阻尼係數 
	
	public ReboundHScrollView(Context context)
	{
		super(context);
	}

	public ReboundHScrollView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
	}

	public ReboundHScrollView(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
	}
	
	@Override  
    protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent)
	{   
    	int newDeltaX = deltaX;
    	int delta = (int) (deltaX * SCROLL_RATIO);
    	if((scrollX+deltaX)==0 || (scrollX-scrollRangeX+deltaX)==0){ 
			newDeltaX = deltaX;		//回彈最後一次滾動，復位
		}else{
			newDeltaX = delta;		//增加阻尼效果
		}
        return super.overScrollBy(newDeltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, MAX_SCROLL, maxOverScrollY, isTouchEvent);    
    }
}