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

I'm fairly certain that the backBarButtonItem is a read-only property. Instead of modifying the backBarButtonItem, try setting a custom leftBarButtonItem and hide the backBarButtonItem:

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

You will also need to make sure you hook up the custom button to call the back action on the UINavigationBar.

Answer 2

I would be willing to bet that this is a bug on Apple's part as I am running into the exact same problem. The reason being is that I can get a custom UIBarButtonItem to appear, but only when I don't try to use the initWithCustomView: method. Per the API, the navigation controller checks the following things when a new view controller is pushed:

1. If the new top-level view controller has a custom left bar button item, that item is displayed. To specify a custom left bar button item, set the leftBarButtonItem property of the view controller’s navigation item.
2. If the top-level view controller does not have a custom left bar button item, but the navigation item of the previous view controller has a valid item in its backBarButtonItem property, the navigation bar displays that item.
3. If a custom bar button item is not specified by either of the view controllers, a default back button is used and its title is set to the value of the title property of the previous view controller—that is, the view controller one level down on the stack. (If there is only one view controller on the navigation stack, no back button is displayed.)

My case (as well as yours) is 2. I specify code exactly the same as yours (i.e., creating a UIButton, setting its image properties for various states, creating a UIBarButtonItem, initializing it with the UIButton, then setting my current view controller's backBarButtonItem property to the UIBarButtonItem); however, when I later push my view controller, nothing at all is displayed on the left-hand side of my navigation controller. Strangely, I can click where the "Back" button should be, and it pops the view controller.

Interestingly, if I create a UIBarButtonItem using the initWithTitle:style:target:action: method instead of the initWithCustomView: method, it does show a custom button with a custom title. Also, as Travis mentioned, using the leftBarButtonItem property instead works just fine. I'd rather adhere to the sanctioned logic, however, by specifying the "Back" button for the current view controller -- to be displayed later when a new view controller is pushed -- instead of creating a left button for the next view controller, which, arguably, should have no concern for anything pertaining to the view controller that came before it. :-\

Answer 3

backBarButtonItem is not a read-only property. I'm not sure why it behaves so strangely, and the above is a valid (if less-than-ideal) workaround.

It behaves strangely because setting a vc's backBarButtonItem doesn't change anything about the appearance of the vc's navigation item - instead, it changes the button that points BACK to the vc. See updating the navigation bar from Apple FMI.

That said I haven't had a whole lot of luck getting it to work myself. If you look around this site, you'll find some threads that suggest placing code very similar to what you already have immediately before the call to push a new view on the stack. I've had some luck there, but unfortunately not when it comes to using a custom image.

Answer 4

Even though is already answered this worked for me:

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"backArrow.png"] style:UIBarButtonItemStyleBordered target:nil action:nil];
self.navigationItem.backBarButtonItem = backButton;
[backButton release];

BTW: even in iOS4 initializing my back button with initWithCustomView: didn't work for me. ;(

Answer 5

I too have been having problems with customView on a navigationItem.backBarButtonItem. I suspect it's probably just b0rked in the SDK.

While the workarounds outlined here do work, I've come up with a solution which is a little more elegant: it still uses navigationItem.leftBarButtonItem, but takes care of it for you automagically (no more need for 'child' view controllers to need to know anything about their 'parent' and/or to manually set navigationItem.leftBarButtonItem).

---

First up, have some class be a UINavigationControllerDelegate for the UINavigationController whose back button you're interested in. Then, in this class, set up something like the following willShowViewController delegate method:

-(void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated{
    // reference to view controller stack
    NSArray *viewControllers = [ navigationController viewControllers ];
    if( [ viewControllers count ] > 1 ){
        // the view controller we'll be linking to
        UIViewController *backViewController = [ viewControllers objectAtIndex: [ viewControllers count ] - 2 ];
        // create custom UIBarButtonItem
        UIBarButtonItem *leftButton = [[ UIBarButtonItem alloc ] initWithCustomView: someCustomView ];
        // set it as the leftBarButtonItem on the incoming viewcontroller
        viewController.navigationItem.leftBarButtonItem = leftButton;
        // tidy up
        [ leftButton release ];
    }
}

I had some further problems with this; it seems that UIBarButtonItem.action and UIBarButtonItem.target don't work when it's a navigationItem.leftBarButtonItem. So, you're left with a custom back button that doesn't actually go back. I'll leave responding to touches in your custom view as an exercise for the reader (I used a UIButton), but you'll need add this method to your delegate class:

-(void)onDummyBackButtonTapped{
    [ someNavigationController popViewControllerAnimated: YES ];
}

and hook it up to fire when your custom view is tapped.

Answer 6

I never been able to create a proper UIBarButtonItem with custom view and setBackBarButtonItem.

Here's the solution i found : let net UINavigationControllerDelegate handles everything! The trick here is to call the popViewControllerAnimated: method of the viewController.navigationController so you don't have to create any custom method.

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    if([navigationController.viewControllers count ] > 1) {
        UIView *backButtonView = [[UIView alloc] initWithFrame:CGRectMake(0,0,70,35)];
        UIButton *myBackButton = [[UIButton buttonWithType:UIButtonTypeCustom] retain];
        [myBackButton setFrame:CGRectMake(0,0,70,35)];
        [myBackButton setImage:[UIImage imageNamed:@"back.png"] forState:UIControlStateNormal];
        [myBackButton setEnabled:YES];
        [myBackButton addTarget:viewController.navigationController action:@selector(popViewControllerAnimated:) forControlEvents:UIControlEventTouchUpInside];
        [backButtonView addSubview:myBackButton];
        [myBackButton release];
        UIBarButtonItem* backButton = [[UIBarButtonItem alloc] initWithCustomView:backButtonView];
        viewController.navigationItem.leftBarButtonItem = backButton;
        [backButtonView release];
        [backButton release];
    }
}

Answer 7

The navigationController's backBarButtonItem is set on the item whose title you're trying to affect.

i.e. in Page 1's view controller, say, viewdidLoad:

self.title = @"Page 1 of 4";

self.navigationItem.backBarButtonItem =
[[[UIBarButtonItem alloc] initWithTitle:@"Page 1"
                                  style:UIBarButtonItemStyleBordered
                                 target:nil
                                 action:nil] autorelease];

You would not override this in Page 2.

Documentation for UINavigationItem : backBarButtonItem makes this clear:

When this item is the back item of the navigation bar—when it is the next item below the top item—it may be represented as a back button on the navigation bar. Use this property to specify the back button. The target and action of the back bar button item you set should be nil. The default value is a bar button item displaying the navigation item’s title.