Objective-C代码如下
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
//scrollView已经有拖拽手势，直接拿到scrollView的拖拽手势
UIPanGestureRecognizer *pan = scrollView.panGestureRecognizer;
//获取到拖拽的速度 >0 向下拖动 <0 向上拖动
CGFloat velocity = [pan velocityInView:scrollView].y;
if (velocity <- 5) {
//向上拖动，隐藏导航栏
[self.navigationController setNavigationBarHidden:YES animated:YES];
}else if (velocity > 5) {
//向下拖动，显示导航栏
[self.navigationController setNavigationBarHidden:NO animated:YES];
}else if(velocity == 0){
//停止拖拽
}
}
swift代码如下
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)
}
}
