iOS判断UITableView的滑动方向

-(void)scrollViewWillBeginDragging:(UIScrollView*)scrollView{
    lastContentOffset = scrollView.contentOffset.y;
    }
 -( void )scrollViewDidScroll:( UIScrollView *)scrollView {
    if (scrollView.contentOffset.y< lastContentOffset )
    {
    //向上
    [ self.navigationControllersetNavigationBarHidden : NOanimated : YES ];
    } else if (scrollView. contentOffset.y >lastContentOffset )
    {
    //向下
    [ self.navigationControllersetNavigationBarHidden : YESanimated : YES ];
    }
    }