"The beginning is the most important part of the work." Plato
冰之依韩版女装（程序媛福利）
–核心代码–
-(void)scrollViewWillBeginDragging:(UIScrollView*)scrollView{
//使用的时候用全局变量
CGFloat lastContentOffset = scrollView.contentOffset.y;
}
-( void )scrollViewDidScroll:( UIScrollView *)scrollView {
if (scrollView.contentOffset.y < lastContentOffset )
{
//向上
NSLog(@"向上");
} else if (scrollView. contentOffset.y >lastContentOffset ){
//向下
NSLog(@"向下");
}
}