以编程方式为 ViewController 创建选项卡栏

我一直在考虑以编程方式向我的视图控制器添加一个选项卡栏，因为有一个滚动视图，如果它不在我的视图中间，我就无法将其放置在上面。我对如何添加它有点困惑。是否需要在我的ViewDidLoad方法或我的AppDelegate？ 如果我有：

UITabBarController  *tabBar = [[UITabBarController alloc] init];
[self.view addSubview:tabBar.view];
[tabBar release]; 

我怎样才能将它分配到我的底部scrollview?

Thanks!

现在在我的 appDelegate 类中：

     self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

   self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
    UITabBarController *tabBarController = [[UITabBarController alloc] init];

    ViewController* vc = [[ViewController alloc] init];


    NSArray* controllers = [NSArray arrayWithObjects:vc, tabBarController, nil];
    tabBarController.viewControllers = controllers;

    [_window addSubview:tabBarController.view];

   self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
   return YES;

}

它崩溃了，不确定它是否是我错过的版本。

Edit:对于 Appdelegate.m 中其他想知道这一点的人：

self.tabBarController = [[[UITabBarController alloc] init] autorelease];
self.tabBarController.viewControllers = @[viewController1, viewController2, viewController3, viewController4];

看看Apple给出的这个文档：视图控制器 http://developer.apple.com/library/ios/#featuredarticles/ViewControllerPGforiPhoneOS/Introduction/Introduction.html.

示例代码：

- (void)applicationDidFinishLaunching:(UIApplication *)application {
   UITabBarController *tabBarController = [[UITabBarController alloc] init];

   FirstViewController* vc1 = [[FirstViewController alloc] init];
   SecondViewController* vc2 = [[SecondViewController alloc] init];

   NSArray* controllers = [NSArray arrayWithObjects:vc1, vc2, nil];
   tabBarController.viewControllers = controllers;

   // Add the tab bar controller's current view as a subview of the window
   [window addSubview:tabBarController.view];
}