Question

I’m using the following code to try to make a “back” button for my app, the view that this code is located is in a modal view (if that has any bearing?):

navBar = [[UINavigationController alloc] initWithRootViewController:tvController];

[navBar.view setFrame:CGRectMake(0, 0, 320, 460)];
self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle: @"Back"
                                                                           style: self.navigationController.navigationItem.leftBarButtonItem.style
                                                                          target: self
                                                                          action: @selector(backAction)];
navBar.navigationItem.backBarButtonItem.enabled = YES;

[self.view addSubview:navBar.view];

The view does not show at all, thank you for any tips!

EDIT: Even if I use a leftBarButtonItem, it still does not show up, I think there is some problem with the self.navigationItem bit of my code?

Answer 1

You need to make sure that when you present the modal view that you wrap it in a UINavigationController, then you’ll have a valid navigation bar to manipulate. Otherwise you’ll change the navigationItem all you want but it won’t show up because you’re not in a navigationController.

So when you go to present the view controller you’re probably doing something like this.

SomeViewController *someViewController = [[[SomeViewController alloc] init] autorelease];
[self presentModalViewController:someViewController animated:YES];

What you want to do is present it like this

SomeViewController *someViewController = [[[SomeViewController alloc] init] autorelease];
UINavigationController *navigationController = [[[UINavigationController alloc] initWithRootViewController:someViewController] autorelease]
[self presentModalViewController:navigationController animated:YES];

Then when you’re in the modal view you’ll have a valid navigation bar that you can manipulate. Altering the leftBarButtonItem at that point will actually do something and be visible.

If you’re trying to make this show a back button though you’re probably “doing it wrong” typically if you’re presenting something modally like this you’d show a “done” button. However by wrapping this with a navigation controller like this it does allow the modal view to then push and pop view controllers and operate as a normal navigation stack. But the root of it should probably have a “done” button not a back to return back to its previous state.