options for TabBar/UITabBarController implementations - iphone

Question

I am new to xcode and trying to understand how UITabBarController works. I have been looking everywhere and could not find a straight solution to this question. In the majority of the examples/tutorials that I see, the UITabBarController is defined in the AppDelegate, and then once you launch the app, you see the tab bar right away. In my app, I want to show a welcome screen first, then once you click "Enter" you get to the tabbar view. So the ideal structure of my objects will be the following:
MyProjectAppDelegate --> MyProjectViewController --> FirstView / SecondView
As far as my understanding, nothing tabbar related should then be declared in MyProjectAppDelegate with this structure. I tried to look at some examples where the UITabBarController is declared in the AppDelegate and do the same in the MyProjectViewController, but nothing happens.
For example, I did this in my MyProjectViewController within an IBAction that is connected to the "Enter" UiButton on my welcome screen:
- (IBAction) EnterApp {
[window addSubview:tabBarController.view];
tabBarController = [[UITabBarController alloc] init];
tabBarController.delegate=self;
FirstView* first = [[FirstView alloc] init];
UINavigationController *firstNav = [[UINavigationController alloc] initWithRootViewController:first];
SecondView* second = [[SecondView alloc] init];
UINavigationController *secondNav = [[UINavigationController alloc] initWithRootViewController:second];
NSArray* controllers = [NSArray arrayWithObjects:firstNav,secondNav, nil];
tabBarController.viewControllers = controllers;
[window addSubview:tabBarController.view];
}
Again, this did not do anything once I clicked on the "Enter" button, even though it does the job in the example where I took it from (where it's within the AppDelegate)
I also tried this on my MyProjectViewController, where the tabbar did show up on the First/Second view, but with no option to customize it (just blank black bars with nothing on them and no idea where to configure them):
- (IBAction) EnterApp {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
UIViewController *viewController1 = [[FirstView alloc] initWithNibName:#"FirstView" bundle:nil];
UIViewController *viewController2 = [[SecondView alloc] initWithNibName:#"SecondView" bundle:nil];
self.tabBarController = [[UITabBarController alloc] init];
self.tabBarController.viewControllers = [NSArray arrayWithObjects:viewController1, viewController2, nil];
self.window.rootViewController = self.tabBarController;
[self.window makeKeyAndVisible];
}
What went wrong here and what should be the right way to go about doing that? A quick example would be highly appreciated.
Thanks!

Answer 1

I have something similar in one of my apps. At first launch it shows a login screen. After the user successfully logs in, the app switches to a tab bar controlled view.
I do the switching in my appdelegate. The login view sends a notification which the app delegate observes and rebuilds the screen:
- (void)switchView:(NSNotification *)notification {
MyTabbarView *homeView = [[MyTabbarView alloc] init];
NSArray *controllers = [NSArray arrayWithObject:homeView];
[mainNavController setViewControllers:controllers animated:YES];
mainNavController.navigationBar.barStyle = UIBarStyleBlack;
mainNavController.navigationBar.hidden = NO;
[homeView release];
}