问题：self.navigationController隐藏导航栏返回上一层，使用方法为
- (void)viewWillAppear:(BOOL)animated{
[superviewWillAppear:animated];
self.navigationController.navigationBar.hidden = YES;
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
self.navigationController.navigationBar.hidden = NO;
}
会出现返回上一层一闪的情况。
解决：
用如下方法代替
[self.navigationController setNavigationBarHidden:YES animated:YES];
[self.navigationController setNavigationBarHidden:NO animated:YES];
