Back button in standalone UINavigationBar with UINavigationController - ios

Question

I am trying to implement a push-up UINavigationBar, where the position of the navigation bar is attached to the contentOffset of the UIScrollView (similar to how safari works in ios7).
In order to get the dynamic movement working I am using a UINavigationBar created programatically and added as a subview of the UIViewController's view (it is accessible as self.navbar).
The UIViewController is within a UINavigationController hierarchy, so I am hiding the built-in self.navigationController.navigationBar at the top of -viewWillAppear:.
The problem I am trying to solve is to add a back button to this new standalone navbar. I would preferably like to simply copy the buttons or even the navigationItems from the navigationController and its hidden built-in navbar, but this doesnt seem to work
Is my only solution to set leftBarButtonItem on my standalone navbar to be a fake back button (when there is a backItem in the navController's navbar)? This seems a bit hacky, and I'd rather use the built backButton functionality.

Answer 1

Another way to do that, once you have your own UINavigationBar set, is to push two UINavigationItems on your navigationBar, causing back button to appear. You can then customize what happens when the back button is pressed.
Here's how I did that
1 - Some UINavigationItem subclass, to define extra-behavior / customization parameters
#interface MyNavigationItem : UINavigationItem
//example : some custom back action when 'back' is pressed
#property (nonatomic, copy) void (^onBackClickedAction)(void);
#end
2 - Then wire that into your UINavigationBarDelegate :
- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item
{
if ([item isKindOfClass:[MyNavigationItem class]]) {
MyNavigationItem *navItem = (MyNavigationItem *)item;
//custom action
if (navItem.backAction) {
navItem.backAction();
}
return YES;// return NO if you don't want your bar to animate to previous item
} else {
return YES;
}
}
You could adapt that scheme, calling your UINavigationController pop method on back action.
This is still hacky

Answer 2

Vinzzz' answer was a good solution. Here is my implementation, as the context was slightly different.
In the UIViewController's viewDidLoad method I setup my navbar's navigation items like this:
NSMutableArray* navItems = [#[] mutableCopy];
if (self.navigationController.viewControllers.count > 1)
{
NSInteger penultimateIndex = (NSInteger)self.navigationController.viewControllers.count - 2;
UIViewController* prevVC = (penultimateIndex >= 0) ? self.navigationController.viewControllers[penultimateIndex] : nil;
UINavigationItem* prevNavItem = [[UINavigationItem alloc] init];
prevNavItem.title = prevVC.title;
[navItems addObject:prevNavItem];
}
UINavigationItem* currNavItem = [[UINavigationItem alloc] init];
... <Add any other left/right buttons to the currNavItem> ...
[navItems addObject:currNavItem];
[self.navbar setItems:navItems];
...where self.navbar is my floating stand-alone UINavigationBar.
I also assign the current view controller to be self.navbar's delegate, and then listen for the -navigationBar:shouldPopItem: event that is triggered when the back button is pressed:
- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item
{
if (navigationBar == self.navbar)
{
[self.navigationController popViewControllerAnimated:YES];
return NO;
}
return YES;
}
(If you return YES, it will crash when a swipe gesture is used in ios7).