UINavigationBar处理

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

[self.navigationController.navigationBar setBackgroundImage:nil forBarPosition:UIBarPositionAny barMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar.clipsToBounds = YES;

self.navigationController.navigationBar.shadowImage = [UIImage new];