删除UINavigationBar上的背景图像

Question

My app uses a navigation controller with an image on in the navigation bar of the home page. The background image is done by putting

[navigationController.navigationBar setBackgroundImage:navImage forBarMetrics:UIBarMetricsDefault];
[_window addSubview:navigationController.view];

in the app delegate. The nav bar displays this image fine.

Every other view will not have an image in the navigation bar. Therefore, I need to remove this background image when any other view controller is pushed. Does anyone know how this can be done?

There are many answers online about adding or changing a nav bar image, but this question is a little bit different. Thank you in advance.

Answer 1

To remove UINavigationBar background in iOS 5 or later, you should do this:

[navigationController.navigationBar setBackgroundImage:nil forBarMetrics:UIBarMetricsDefault];

Hope it helps

Answer 2

You can set background image with blank image created in runtime.

UIGraphicsBeginImageContextWithOptions(CGSizeMake(36, 36), NO, 0.0);
UIImage *blank = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[[UINavigationBar appearance] setBackgroundImage:blank forBarMetrics:UIBarMetricsDefault];

Creating blank image in runtime: How to create a blank transparent png in Objective-C?

Answer 3

I believe this to be the first actual answer to this for iOS5, the main problem being the "removal" of the background image once you are done. Well, just retain the existing image and put it back when you are done.

@implementation MyViewController {
    UIImage *_defaultImage;
}

- (void)viewWillAppear:(BOOL)animated {   
    _defaultImage = [self.navigationController.navigationBar backgroundImageForBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"bar.png"] forBarMetrics:UIBarMetricsDefault];
}

- (void)viewWillDisappear:(BOOL)animated {
    [self.navigationController.navigationBar setBackgroundImage:_defaultImage forBarMetrics:UIBarMetricsDefault];
}

Answer 4

Nothing here have worked for me. After searching for hours, the only thing that worked was following a source code example provided by Apple.

I placed the following code and it worked and removed the navigation bar image from other view controllers finally!!

// Reset everything about navigation bar. (Other flows' background image used to show up on another view controller)
    self.navigationController!.navigationBar.setBackgroundImage(nil, for: .default)
    self.navigationController!.navigationBar.setBackgroundImage(nil, for: .compact)
    self.navigationController!.navigationBar.barTintColor = nil
    self.navigationController!.toolbar.barTintColor = nil
    self.navigationController!.toolbar.isTranslucent = true

Hope this helps someone.

Cheers

Answer 5

It looks like the easiest way to do this is to:

1) set the alpha of the navigation bar on the home page to 0.000001

2) put the background image in a UIImageView "behind" the navigation bar (which is now clear)

3) use viewWillAppear / viewWillDisappear to set the navigation bar's opacity to either 1 or 0.00001 when views are pushed / popped.