iOS 视图滚动到某一个位置做某一件事

#pragma UIScrollView
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
if ([[UIDevice
currentDevice] userInterfaceIdiom] ==
UIUserInterfaceIdiomPhone) {
return (interfaceOrientation !=
UIInterfaceOrientationPortraitUpsideDown);
} else {
return
YES;
}
}

//隐藏导航栏的方法
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

NSLog(@"scrollViewDidScroll---->%f",self.myTableView.contentOffset.y);

if (self.myTableView.contentOffset.y >=
171)
{
self.addNavBar.hidden =
YES;
NSLog(@"隐藏导航栏");
}
if (self.myTableView.contentOffset.y <=
171) {

}

}