导航栏透明

self.navigationController.navigationBar.titleTextAttributes = @{NSForegroundColorAttributeName:[UIColor whiteColor]};
self.navigationController.navigationBar.tintColor = [UIColor whiteColor];
self.navigationController.navigationBar.translucent = YES;
[self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar.shadowImage = [UIImage new];