Question

How would I ‘punch a hole’ in a tab bar app, whereby a tab-bar based app can show a view behind the uinavigationcontrollers that are in each tab? (this punch could be optionally turned off).

My code, the the app delegate, for creating the tabs is:

OneRootViewController *oneRootViewController = [[OneRootViewController alloc] initWithNibName:@"OneRootViewController" bundle:nil];
UINavigationController *oneNav = [[UINavigationController alloc] initWithRootViewController:oneRootViewController];
oneNav.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"One" image:[UIImage imageNamed:@"one.png"] tag:0];

TwoRootViewController *twoRootViewController = [[TwoRootViewController alloc] initWithNibName:@"TwoRootViewController" bundle:nil];
UINavigationController *twoNav = [[UINavigationController alloc] initWithRootViewController:twoRootViewController];
twoNav.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"Two" image:[UIImage imageNamed:@"two.png"] tag:1];

self.tabBarController = [[UITabBarController alloc] init];
self.tabBarController.viewControllers = [NSArray arrayWithObjects:oneNav, twoNav, nil];
self.window.rootViewController = self.tabBarController;
[self.window makeKeyAndVisible];

Here’s how I’d like it to work:

-----------------------------
|                           |
|     ---------------       |
|     |             |       |
|     | hole which  |       |
|     | shows the   |       |
|     | same view   |       |
|     | in each tab |       |
|     ---------------       |
|                           |
|                           |
-----------------------------
|            |              |
|   tab 1    |   tab 2      |
|            |              |
-----------------------------

There’s a thread here about transparent rectangles – iPhone – Draw transparent rectangle on UIView to reveal view beneath – but I’m not sure how to do it in my case.. would I subclass my nav controller or tab bar controller (is it legal to even do that), and if so, how would I make the hole optional?

Answer 1

Why not just add an UIView (which will act as a “hole”) on top of the Tab-bar controller?

You may just add it to application’s UIWindow, like this, in application:didFinishLaunchingWithOptions::

// ...
self.window.rootViewController = self.tabBarController;

MyView *holeView = [[MyView alloc] initWithFrame:CGRectMake(hole coordinates)];
[self.window addSubview:holeView];
[holeView release];

[self.window makeKeyAndVisible];