iOS NavigationBar隐藏

当一有个需求是首页的navBar隐藏，而二级页面的照常显示的时候你要这么隐藏

  -(void)viewWillAppear:(BOOL)animated
{
[self.navigationController setNavigationBarHidden:YES animated:animated];

[super viewWillAppear:animated];
int x = ((int)self.mainScorllView.scrollView.contentOffset.x )/ MYUISCREEN_WIDTH;
self.mainScorllView.scrollView.contentOffset = CGPointMake(x*MYUISCREEN_WIDTH , 0) ;

}

  - (void)viewWillDisappear:(BOOL)animated {
[self.navigationController setNavigationBarHidden:NO animated:animated];
[super viewWillDisappear:animated];
  }