Custom TabBarController functionality - ios

Question

I'm attempting to create a custom tab bar controller with the following options:
Feed
Map
New
Camera
Search
The feed, map, camera, and search will each pull up their individual VC's, while new is supposed to be more of a functionality button. When the new tab item is pressed, the map view should be displayed, and the map should begin recording the user's location. I'm trying to use a UITabBarController to manage these views, but I cannot seem to figure out how to implement the functionality that I would like with the "New" tab. It seems as if I would need to implement a separate view controller for the "New" record and stop functionality but that doesn't seem right.
The functionality of record/stop should be similar to snapchat's big red button that takes a picture when you press it.

Answer 1

While I agree with Scott's comment that this is a bad UX, if you technically wanted to do it, you could subclass UITabBarController and in viewDidLoad you could add a UIButton subview to the the tab bar controller's tabBar:
[self.tabBar addSubview:yourCustomButton];
Thus, this button could have it's own action and selector to do whatever you want with.
Take a look at idevrecipes for an example.

Answer 2

I think you have to implement the container view controller yourself. I think you can't do that with UITabBarController.

Answer 3

I was going to dig up the idevrecipes example that shawnwall pointed out, but there's another possibly answer, assuming you want the New button to match the standard UITabBarButton appearance. I agree it may not be the best UI, but it's workable.
For starters, you would create a dummy view controller for the New item. I'm not saying you should duplicate the Maps controller or anything, I'm just saying create an empty view controller and stash to it (or it's location) in a property. Assuming you're creating your tab bar in application:didFinishLaunchingWithOptions:, it'd look something like this.
self.newViewController = [[UIViewController alloc] init];
self.newViewController.title = NSLocalizedString(#"New", nil);
self.newViewController.image = [UIImage imageNamed:"new.png"];
Drop that view controller at the appropriate location in the tab bar controller's viewControllers property.
Save a reference to the Maps controller the same way you saved one for the dummy New controller.
If you haven't already done do, set the delegate of your tabBarController to your app delegate. You may need to declare that your app delegate conforms to UITabBarControllerDelegate.
UITabBarDelegate gives you a few hooks for tracking changes to the tab bar. tabBarController:shouldSelectViewController: looks to be the appropriate place for us to hook in for your desired behavior.
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController
{
if ([viewController isEqual:self.newViewController]) {
self.tabBarController.selectedViewController = self.mapViewController;
// Whatever logic you need to start the recording
return NO;
}
return YES;
}
The look of the user interaction's a little odd - the user tabs the middle item (New), but the item to the left (Map) gets selected. If you want the "tab bar triggers behavior" action, I'd go the idevrecipes route and make the button visually distinct. If you're married to the tab bar item look, though, I believe this is how you'd accomplish it.