去掉导航栏阴影
[[UINavigationBar appearance] setTintColor:[UIColor colorWithWhite:0.0 alpha:0.0f]];
//去掉导航栏 的阴影线
self.navigationController.navigationBar.clipsToBounds = YES;
[[UINavigationBar appearance] setTintColor:[UIColor colorWithWhite:0.0 alpha:0.0f]];
//去掉导航栏 的阴影线
self.navigationController.navigationBar.clipsToBounds = YES;