##What is TBNavigationController
TBNavigationController is a custom navigation controller that allows completely custom backBarButtonItems. It does this by not actually using the standard backBarButtonItem, which is limited by Apple to UIBarButtonItem's without custom views, but instead by faking it and using a leftBarButtonItem.
##I need a custom back bar button, what should I do?
If you just want to change the title, you can do this easily using the built in Interface Builder Navigation Item "Back Button" property, or by setting a custom back button in the UIViewController's viewDidLoad.
If you want the standard style back button, but want an image inside the button, you can use the standard self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"yourImage"] ... method in your UIViewController.
If you want the same shape as Apple's back button, but just want a different background color, you can follow this tutorial.
If you don't want the same shape as Apple's back button, but still want basically the same type of back button (i.e. a standard image with some text overlaid over it), you can follow that tutorial and just use a custom resizable image.
If you want a completely custom view for your back button, and are willing to manually set the back button for every child view controller, you can just create a UIBarButtonItem with [UIBarButtonItem initWithCustomView:(UIView *)], set an action and target so that it calls a method which calls popViewControllerAnimated:, and set it as a your view controller's navigationItem.leftBarButtonItem.
If you want a completely custom view for your back button, but only want to have to set the back button for the pushing view controller and have it affect the pushed controllers in an elegant way, the same as how Apple's built-in backBarButtonItem works, you should take a look at TBNavigationController.
##How does it work?
If you need a backBarButtonItem that uses a custom view, normally you are out of luck. Despite the navigationItem.backBarButtonItem property being classed as a UIBarButtonItem*, Apple, in an apparent breach of abstraction, will ignore UIBarButtonItems with custom views. Your only hint to this is a little note tagged onto the discussion section of the backBarButtonItem in Apple's UINavigationItem class reference, which states:
"When configuring your bar button item, do not assign a custom view to it; the navigation item ignores custom views in the back bar button anyway."
This has clearly tripped up a lot of people, as can be seen with the numerous stack overflow questions about their custom back bar button items being ignored. Anyway, it's Apple's API, so I'm sure they have their reasons.
The most obvious way around this restriction is to just make a fake back button: Make a UIBarButtonItem with a custom view, set up its target and action to pop the current view controller, and set it as the leftBarButtonItem of the pushed view controllers you want to change.
This gives you the greatest flexibility in terms of appearance and functionality of the back button, but it has a huge downside: You have to set the back button for each child view controller manually.
To get around this, I subclassed UINavigationController and moved the code that sets the leftBarButtonItem into the NavigationController - (void) pushViewController:(UIViewController *)viewController animated:(BOOL)animated method.
Now, whenever a view is pushed, the view controller looks for a custom back bar button and sets it as the leftBarButtonItem of the viewController to be pushed.
But this is only one part of the system, because we also need some way to associate a custom backBarButtonItem with every UIViewController instance, the way Apple already has a backBarButtonItem property for every UIViewController instance. We could subclass UIViewController, but that wouldn't affect existing subclasses of UIViewController.
Instead, I added a category on UIViewController called CustomBackBarButtonItem. It does only one thing: it adds a property on UIViewController called UIBarButtonItem* customBackBarButtonItem.
With this property, the new custom UINavigationController can look at the pushing view controller's customBackBarButtonItem and set it as the pushed view controller's leftBarButtonItem, replicating the functionality of the normal UINavigationController.
Categories can't actually have instance variables, though, so I used associated objects in the CustomBackBarButtonItem category. I also set it so that it will return a default custom back button if that view has no associated objects. This makes it so that any view which has not set a custom back button can still use a custom default back button that you set for the whole app.
As a convenience, I also have a category on UIBarButtonItem to return the defaultBackButton and to help create UIBarButtonItems that use a UIImageView as a custom view as per this stack overflow response.
##Instructions
- Set the custom class of your navigation controller to
TBNavigationController. - Change the default back button in
UIBarButtonItem+UIBarButtonItem_CustomImageto whatever you want. - On those UIViewControllers that have custom back bar button items, import
UIViewController+UIViewController+CustomBackBarButtonItem.hand possiblyUIBarButtonItem+UIBarButtonItem_CustomImage.h. - Then set
self.customBackBarButtonItemto [UIBarButtonItem barItemWithImage:[UIImage imageNamed:@"someImage.png"] target:nil action:nil];` - You should now have custom back buttons for view controllers that go back to that UIViewController.
##FAQ
###Why did you make this?
My client needed very custom back buttons that look nothing like Apple's. I didn't want to have to manually set back buttons for each page, and subclassing UINavigationController to add my own custom back bar button functionality seemed like the most elegant solution.
###Why upload it?
I thought I was kind of clever using my favorite new Objective-C feature, associated objects, so I thought I should let others take a look.
###What does it look like?
SmileyViewController
UIViewController pushed from SmileyViewController
###Any other nagging concerns?
There might still be a way to achieve the same effects without subclassing UINavigationController. I was experimenting with using transparent resizable images and the UIAppearance protocol, then setting the normal backBarButtonItem property with a UIBarButtonItem initialized with an image. I was able to get something closer to what TBNavigationController does, but the image was still resized and smaller, and required one to manually set the image for other button states (i.e. no automatic tint). This approach did have the advantage of the standard swipe animation, though.
One other thing, you could probably do this without subclassing UINavigationController by using the UINavigationControllerDelegate protocol. The only thing I'm worried about with that approach is it is probably less powerful in terms of adding animations. Anyway, I'm fairly certain that the way I subclassed UINavigationController is pretty safe, but if you are still afraid of subclassing it you could try implementing this functionality in a UINavigationController delegate.
This method loses the standard back button swiping animation, which is kind of a deal breaker for most people.
I'm currently not very familiar with animations, but I think it should be possible to animate the button in the same way as the normal back button. Any help would be appreciated.
##Feedback
I’m very open to feedback, especially bug reports. I’m using some language features I’m new to, so some veteran feedback would be much appreciated.
Copyright 2013 Tyler Barth