CGFloat lastContentOffset;  //ScoreView 滑动位置

-(void)scrollViewWillBeginDragging:(UIScrollView*)scrollView{

     lastContentOffset = scrollView.contentOffset.y;

}

-( void )scrollViewDidScroll:( UIScrollView *)scrollView {

   if (scrollView. contentOffset.y < lastContentOffset )

   {

       //向上，隐藏导航栏

      [ self.navigationController setNavigationBarHidden : NO animated : YES ];

    }

     else if (scrollView. contentOffset.y > lastContentOffset )

    {

       //向下

       [ self.navigationController setNavigationBarHidden : YES animated : YES ];

     }

}