Why is view of UINavigationController root controller smaller than nav controller

Question

I am trying to create a transparent UINavigationBar and here is what I do:

First, I have a navVC and a general VC as root VC in my code.

SNLoginViewController *loginVC = [[SNLoginViewController alloc] init];
SNLoginNavController *loginNavVC = [[SNLoginNavController alloc] initWithRootViewController:loginVC];
[self presentViewController:loginNavVC animated:YES completion:nil];

I didn't override the init method of SNLoginViewController.

And here is the implementation of initWithRootViewController::

- (instancetype)initWithRootViewController:(UIViewController *)rootViewController {
    self = [super initWithRootViewController:rootViewController];
    if (self) {
    
        UIImage *bgImage = [UIImage imageNamed:@"bg"];
        UIImageView *bgImageView = [[UIImageView alloc] initWithImage:bgImage];
        bgImageView.frame = [UIScreen mainScreen].bounds;
        [self.view insertSubview:bgImageView atIndex:0];
    
        [self.navigationBar setBackgroundImage:[UIImage imageNamed:@"transparent"]//transparent is a transparent png
                             forBarMetrics:UIBarMetricsCompact];
        self.navigationBar.shadowImage = [UIImage imageNamed:@"transparent"];
        self.navigationBar.barStyle = UIBarStyleBlackTranslucent;
    
        [self.navigationBar setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor whiteColor], NSFontAttributeName: [UIFont systemFontOfSize:18]}];
        self.navigationBar.clipsToBounds = YES;
    }
    return self;
}

Using these codes (setBackgroundImage:forBarMetrics:) I should have been able to make the navigation bar transparent but something went wrong. The major problem is that somehow the frame of loginVC is smaller than loginNavVC.

_{(source: zybuluo.com)}

In the figure above the selected view is of loginVC and the one on the left is of loginNavVc. loginVC is smaller than loginNavVc.

But in viewDidLoad of loginVC I print the selected view, its frame is (0 0; 320 568) but when I print its description in view hierarchy (same address in memory), its frame is (0 64; 320 504). Why would this happen? How to make it full screen(not full screen like games, status bar should still be visiable)?

Answer 1

Add this before presenting your navigation controller.

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

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

self. loginNavVC.navigationBar.translucent = YES;