navigationBar.translucent = YES无法在呈现的视图控制器

Question

为什么navigationBar.translucent = YES;不适合在呈现的视图控制器中制作半透明导航栏？

self.navigationController.navigationBar.translucent = YES;

这是我的视图控制器呈现代码。

    SettingsViewController *vc = [[SettingsViewController alloc]initWithNibName:@"SettingsViewControllerNew" bundle:nil];
    UINavigationController *navVc = [[UINavigationController alloc]initWithRootViewController:vc];
    navVc.navigationBar.translucent = YES;
    [self presentViewController:navVc animated:YES completion:nil];

但它在根视图和导航视图控制器中工作。怎么了？