UIScrollViewDelegate会经常用到，在这里对代劳协定所包含的办法简单描述，以便于今后应用
几个概念的懂得:
contentSize:可滑动区域的大年夜小
contentOffset:滑动视图琅绫擎的内容的相对地位
contentInset:滑动视图在外面的相对地位
-(void)scrollViewDidScroll:(UIScrollView *)scrollView;
2、将要开端拖拽棘手指已经放在view上并预备拖动的那一刻
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView;
3、将要停止拖拽棘手指已拖动过view并预备分开手指的那一刻，留意：当属性pagingEnabled为YES时，此函数不被调用
-(void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset;
4、已经停止拖拽棘手指刚分开view的那一刻
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
5、view将要开端减速，view滑动之后有惯性
-(void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView;
6、view已经停止滚动
7、view的缩放
-(void)scrollViewDidZoom:(UIScrollView *)scrollView
8、有动画时调用
-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
1、只要view有滚动（不管是拖、拉、放大年夜、缩小等导致）都邑履行此函数
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView;