self.navigationController.hidesBarsOnSwipe = YES; 

self.navigationController?.hidesBarsOnSwipe = true 

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{ //scrollView已經(jīng)有拖拽手勢(shì)，直接拿到scrollView的拖拽手勢(shì) UIPanGestureRecognizer *pan = scrollView.panGestureRecognizer; //獲取到拖拽的速度 >0 向下拖動(dòng) <0 向上拖動(dòng) CGFloat velocity = [pan velocityInView:scrollView].y;  if (velocity <- 5) {  //向上拖動(dòng)，隱藏導(dǎo)航欄  [self.navigationController setNavigationBarHidden:YES animated:YES]; }else if (velocity > 5) {  //向下拖動(dòng)，顯示導(dǎo)航欄  [self.navigationController setNavigationBarHidden:NO animated:YES]; }else if(velocity == 0){  //停止拖拽 }}

func scrollViewDidScroll(scrollView: UIScrollView) {      let pan = scrollView.panGestureRecognizer   let velocity = pan.velocityInView(scrollView).y   if velocity < -5 {    self.navigationController?.setNavigationBarHidden(true, animated: true)   } else if velocity > 5 {    self.navigationController?.setNavigationBarHidden(false, animated: true)   }     } 

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset</span> 

{  if (velocity.y > 0.0) {   [self.navigationController setNavigationBarHidden:YES animated:YES];  } else if (velocity.y < 0.0){   [self.navigationController setNavigationBarHidden:NO animated:YES];  } } 

func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {   if velocity.y > 0 {    self.navigationController?.setNavigationBarHidden(true, animated: true)   } else if velocity.y < 0 {    self.navigationController?.setNavigationBarHidden(false, animated: true)   }  }