iPhone SDK开发基础之
使用UITabBarController组织和管理UIView

当你的程序分为几个相对比较独立的部分时，就比较适合使用UITabBarController来组织用户界面，如图3-26所示。
 

在屏幕的下方包含UITabBarController的三个按钮，用户单击不同的按钮即可以进入不同的界面，每个界面相对来说在整个系统中比较独立，也就是程序分成了三个相对比较独立的不同部分，在每个相对独立的部分你也可以使用UINavigationController等容器类组织你的界面。这样组织使程序逻辑非常清晰，当然你也可以组织很多个Tab而不只是三个，以下代码演示如何创建UITabBarController对象，并为其添加多个Tab。
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions: (NSDictionary *)launchOptions {   

    // Override point for customization after application launch.
 
 //Create the navigation Controller
 UINavigationController *localNavigationController;
 //Create UINavigationController
 tabBarController = [[UITabBarController alloc] init];
    tabBarController.delegate = self;
 // Create the array that will contain all the View controlelr
 NSMutableArray *localControllersArray = [[NSMutableArray alloc] init WithCapacity:3];
 // Create the view controller attached to the first item in the TabBar
 
 aViewController *firstViewController;
 firstViewController = [aViewController alloc];
 localNavigationController = [[UINavigationController alloc] initWithRoot ViewController:firstViewController];
 localNavigationController.navigationBar.barStyle. = UIBarStyleBlackOpaque;
 
 [localNavigationController.tabBarItem initWithTitle:@"Outlines"
 image:[UIImage imageNamed:@"webcast.png"] tag:1];
 firstViewController.navigationItem.title = @"Outlines";
 
 [localControllersArray addObject:localNavigationController];
 [localNavigationController release];
 [firstViewController release];
 
 // Create the view controller attached to the second item in the TabBar
 
 anotherViewController *secondViewController;
 secondViewController = [[anotherViewController alloc] initWithStyle. UITableViewStyleGrouped ];
 localNavigationController = [[UINavigationController alloc] initWithRoot ViewController:secondViewController];
 [localNavigationController.tabBarItem initWithTitle:@"Q & A"
   image:[UIImage imageNamed:@"book.png"] tag:2];
 secondViewController.navigationItem.title=@"Q & A";
 
 [localControllersArray addObject:localNavigationController];
 [localNavigationController release];
 [secondViewController release];
  
 miscViewController *thirdViewController;
 thirdViewController = [[miscViewController alloc] initWithStyle.:UITable ViewStyleGrouped ];
 localNavigationController = [[UINavigationController alloc] initWithRoot ViewController:thirdViewController];
 [localNavigationController.tabBarItem initWithTitle:@"Misc"
   image:[UIImage imageNamed:@"favorites.png"] tag:3];
 thirdViewController.navigationItem.title=@"Misc";
 
 [localControllersArray addObject:localNavigationController];
 [localNavigationController release];
 [thirdViewController release];
 
 // load up our tab bar controller with the view controllers
 tabBarController.viewControllers = localControllersArray;
 
 // release the array because the tab bar controller now has it
 [localControllersArray release];
 // add the tabBarController as a subview in the window
 [window addSubview:tabBarController.view];
 
 // need this last line to display the window (and tab bar controller)
 [window makeKeyAndVisible];
 
    return YES;
}
捕获Tab切换事件，获取当前活动的Tab索引和UIViewController对象，代码如下。
- (void)tabBarController:(UITabBarController *)barController didSelectView Controller:(UIViewController *)viewController{
 
 NSLog(@"currentController index:%d"，viewController， tabBarController.selectedIndex);
 UIViewController  *currentController = tabBarController.selectedView Controller;
 NSLog(@"currentController: %@"，currentController);
   
}
切换不同的Tab时，只需要设置UITabBarController的selectedIndex属性即可，代码如下。
tabBarController.selectedIndex = 2;
本节相关的完整Xcode工程源代码文件请参考本书附带的光盘中的Lessons2实例。

本文节选自《iOS软件开发揭密：iPhone&iPad企业应用和游戏开发》一书。
《iOS软件开发揭密：iPhone&iPad企业应用和游戏开发》一书已由电子工业出版社正式出版，本书由虞斌著。

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