Tab bar controller inside a navigation controller,

Question

I'm trying to implement a UI structured like in the Tweetie app, which behaves as so: the top-level view controller seems to be a navigation controller, whose root view is an "Accounts" table view. If you click on any account, it goes to the second level, which has a tab bar across the bottom. Each tab item shows a different list and lets you drill down further (the subsequent levels don't show the tab bar).

So, this seems like the implementation hierarchy is:

• UINavigationController
  1. Accounts: UITableViewController
  2. UITabBarController
     1. Tweets: UITableViewController
        • Detail view of a tweet/user/etc
     2. Replies: UITableViewController
     3. ...

This seems to work[^1], but appears to be unsupported according to the SDK documentation for -pushViewController:animated: (emphasis added):

viewController: The view controller that is pushed onto the stack. It cannot be an instance of tab bar controller.

I would like to avoid private APIs and the like, but I'm not sure why this usage is explicitly prohibited even when it seems to work fine. Anyone know the reason?

I've thought about putting the tab bar controller as the main controller, with each of the tabs containing separate navigation controllers. The problem with this is that each nav controller needs to share a single root view controller (namely the "Accounts" table in Tweetie) -- this doesn't seem to work: pushing the table controller to a second nav controller seems to remove it from the first. Not to mention all the book-keeping when selecting a different account would probably be a pain.

How should I implement this the Right Way?

[^1]: The tab bar controller needs to be subclassed so that the tab bar controller's navigation item at that level stays in sync with the selected tab's navigation item, and the individual tab's table controller's need to push their respective detail views to self.tabBarController.navigationController instead of self.navigationController.

Answer 1

It's possible to add a UITabBar to any UIViewController. That way you don't actually have to push a UITabBarController and therefore stay within the guidelines of the Apple API.

In interface builder UITabBar is under "Windows, Views & Bars" in the Cocoa Touch Library.

Answer 2

In my app, the root view controller is a UINavigation controller. At a certain point in the app, I need to display a UITabBar. I tried implementing a UITabBar on a UIView within the navigation hierarchy, as some of the previous posts suggested, and this does work. But I found that I wanted more of the default behavior that the tab controller provides and I found a way to use the UITabBarController with the UINavigation controller:

1) When I want to display the UITabBarController's view, I do this:

MyAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
appDelegate.window.rootViewController = myUiTabBarControllerInstance;

2) When I want to return to where I was in the navigation hierarchy, I do this:

appDelegate.window.rootViewController = myNavControllerInstance;

Answer 3

I wrote a blog post on how I approached this problem. For me, using a modal view was a simpler solution than writing a custom tab-bar implementation.

http://www.alexmedearis.com/uitabbarcontroller-inside-a-uinavigationcontroller/