Updating navigation bar after a change using UIAppearance

Question

I'm currently customising the navigation bar background image of my iOS app using the UIAppearance proxy. There is a button for switching between two different modes which triggers a notification. This notification will change the background to a different image using again the proxy. My problem is that this change becomes visible only when I go to a different controller and I come back to it. I'm not able to force the update of the navigation bar within the controller.

I've tried this in my MainTabBarController:

- (void) onAppChangedMode: (NSNotification*)notif {

APP_MODE mode = (APP_MODE) [[notif object] integerValue];

// change navigation bar appearance
[[UILabel appearance] setHighlightedTextColor:[UIColor redColor]];
[[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:(mode == 0 ? @"navbar.png" : @"navbar2.png")] forBarMetrics:UIBarMetricsDefault];
// trying to update
for (UIViewController* vc in self.viewControllers) {
     [vc.navigationController.navigationBar setNeedsDisplay];
}

}

but nothing...it's not working. Any idea how to achieve it?

Thanks!

Rafe

I don't know why, but the changes to uiappearance at runtime won't apply to any loaded views. However, you can immediately apply the changes on the loaded views themselves. – Clarence

does it mean I cannot use UIAppearance but I have to set each bar separately – Rafe

No. You can use UIAppearance but the displayed views won't be affected. So the one displayed bar you should set explicitly. – Clarence

I wonder if it's a bug – Rafe

I don't think so. UIAppearance is a convenient way to specify the appearance of your whole app, a task that typically is done once at app startup. – Clarence

I agree,but this limitation makes the whole visual context switching quite cumbersome. – Rafe

Can you reply to the question not in comment? I think your answer it's the correct one and I would like to assign it to you. – Rafe

Answer 1

Try this code to change the background image for the current nav bar only:

[self.navigationController.navigationBar setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];

Use the above code after changing the UIAppearance. This will force a change in the nav bar of the current controller. The nav bars for the other controllers will be handled by the change in UIAppearance.

Cinthiacintron

edited my answers. Use the above code TOGETHER with your code in changing the UIAppearance. – Cinthiacintron

Answer 2

Just remove views from windows and add they again:

for (UIWindow *window in [UIApplication sharedApplication].windows) {
    for (UIView *view in window.subviews) {
        [view removeFromSuperview];
        [window addSubview:view];
    }
}

Arredondo

This works perfectly for me. It doesn't appear to have any performance issues and is effective immediately. – Knock

As per Apple's docs: developer.apple.com/documentation/uikit/uiappearance: iOS applies appearance changes when a view enters a window, but it doesn’t change the appearance of a view that’s already in a window. To change the appearance of a view that’s currently in a window, remove the view from the view hierarchy and then put it back. – Carmichael

Answer 3

I just have the same problem, this code will help you:

- (IBAction)btnTouched:(id)sender {
    [[UADSwitch appearance]setOnTintColor:[UIColor redColor]];

    // Present a temp UIViewController 
    UIViewController *vc = [[UIViewController alloc]init];
    [self presentViewController:vc animated:NO completion:nil];//"self" is an instance of UIViewController
    [vc dismissViewControllerAnimated:NO completion:nil];
}

Pinzler

+1 Used your method and got a warning/problem with my UITabBarController: Warning: Attempt to present <UIViewController: 0x83ea6e0> on <MNCalendarsTabBarControllerViewController: 0x86861a0> whose view is not in the window hierarchy!. So I modified your solution by replacing self with UIViewController *presentingController = [[[[UIApplication sharedApplication] delegate] window] rootViewController]; [presentingController presentViewController: viewController animated: YES completion: nil];, found here - and it worked. Tanks, took me hours. – Yuriyuria