cocoa touch - How to create backBarButtomItem with custom view for a UINavigationController

Question

I have a UINavigationController into which I push several views. Inside viewDidLoad for one of these views I want to set the self.navigationItem.backBarButtonItem to a custom view (based on a custom image). I don't know why, but it doesn't seem to work. Instead, I get the standard "back" button.

UIButton *backButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 63, 30)];
[backButton setImage:[UIImage imageNamed:@"back_OFF.png"] forState:UIControlStateNormal];
[backButton setImage:[UIImage imageNamed:@"back_ON.png"] forState:UIControlStateSelected];
UIBarButtonItem *backButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backButton];
self.navigationItem.backBarButtonItem = backButtonItem;
[backButtonItem release];
[backButton release];

I tested with a standard title and it worked. What is wrong with the above code ?

self.navigationItem.backBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Prout" style:UIBarButtonItemStyleDone target:nil action:nil] autorelease];

Thanks for any help on this.

Answer 1

As of iOS5 we have an excellent new way of customizing the appearance of almost any control using the UIAppearance protocol, i.e. [UIBarButtonItem appearance]. The appearance proxy allows you to create application wide changes to the look of controls. Below is an example of a custom back button created with the appearance proxy.

Use the example code below to create a back button with custom images for normal and highlighted states. Call the following method from you appDelegate's application:didFinishLaunchingWithOptions:

- (void) customizeAppearance {

UIImage *i1 = [[UIImage imageNamed:@"custom_backButton_30px"]
                      resizableImageWithCapInsets:UIEdgeInsetsMake(0, 15, 0, 6)];
UIImage *i2 = [[UIImage imageNamed:@"custom_backButton_24px"] 
                      resizableImageWithCapInsets:UIEdgeInsetsMake(0, 15, 0, 6)];

[[UIBarButtonItem appearance] setBackButtonBackgroundImage:i1 
                              forState:UIControlStateNormal 
                              barMetrics:UIBarMetricsDefault];

[[UIBarButtonItem appearance] setBackButtonBackgroundImage:i2 
                              forState:UIControlStateNormal 
                              barMetrics:UIBarMetricsLandscapePhone];

[[UIBarButtonItem appearance] setBackButtonBackgroundImage:i1
                              forState:UIControlStateHighlighted 
                              barMetrics:UIBarMetricsDefault];

[[UIBarButtonItem appearance] setBackButtonBackgroundImage:i2 
                              forState:UIControlStateHighlighted 
                              barMetrics:UIBarMetricsLandscapePhone];
}

This is just a quick example. Normally you would want to have separate images for normal and highlighted (pressed) state.

If you are interested in customizing the appearance of other controls, some good examples can be found here: http://ios.biomsoft.com/2011/10/13/user-interface-customization-in-ios-5/