uinavagation 透明代码

NSShadow *shadow = [[NSShadow alloc] init];

[shadow setShadowOffset:CGSizeMake(1, 1)];

[shadow setShadowColor:[UIColor blackColor]];

[shadow setShadowBlurRadius:1];

self.navigationController.navigationBar.titleTextAttributes = @{NSForegroundColorAttributeName: [UIColor blackColor], NSShadowAttributeName: shadow};

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

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