隐藏导航栏UINavigationBar底部黑线

全局隐藏

[[UINavigationBar appearance]  setBackgroundImage:[[UIImage alloc] init] forBarPosition:UIBarPositionAny barMetrics:UIBarMetricsDefault];
[[UINavigationBar appearance] setShadowImage:[[UIImage alloc] init]];

或者

[UINavigationBar appearance].clipsToBounds = YES;

局部隐藏

[self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
[self.navigationController.navigationBar setShadowImage:[UIImage new]];

或者

self.navigationController.navigationBar.clipsToBounds=YES;