UITabBarController

1.- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
2.    // Override point for customization after application launch.
3.    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
4.    self.window.backgroundColor = [UIColor whiteColor];
5.    [self.window makeKeyAndVisible];
6.
7.    ViewController *rootController = [[ViewController alloc] init];
8.    SecondViewController *second = [[SecondViewController alloc] init];
9.
10.    UITabBarController *tabBarController = [[UITabBarController alloc] init];
11.    [tabBarController addChildViewController:rootController];
12.    [tabBarController addChildViewController:second];
13.
14.
15.    UITabBarItem *item = [[UITabBarItem alloc] initWithTitle:nil
16.                                                       image:[UIImage imageNamed:@"tabbar_sound_n"]
17.                                               selectedImage:[UIImage imageNamed:@"tabbar_sound_h"]];
18.
19.    rootController.tabBarItem = item;
20.    rootController.tabBarItem.badgeValue = @"123";
21.
22.    UITabBarItem *secondItem = [[UITabBarItem alloc] initWithTitle:nil
23.                                                       image:[UIImage imageNamed:@"tabbar_me_n"]
24.                                               selectedImage:[UIImage imageNamed:@"tabbar_me_h"]];
25.
26.    second.tabBarItem = secondItem;
27.
28.
29.    [self.window setRootViewController:tabBarController];
30.
31.    return YES;
32.}
33.

• 设置消息提醒个数即为：viewController.tabBarItem.badgeValue = @"123"
• 有时我们需要将用户退出程序时所选中动视图控制器索引保存下来，以便下次用户重新进入程序时程序还是之前退出时的状态。
  tabBarController.delegate = self;
  并实现方法：

1.-(void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{
2.
3.    //用于保存用户偏好设置
4.    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
5.    [userDefaults setInteger:tabBarController.selectedIndex forKey:@"selectedIndex"];
6.    [userDefaults synchronize];//强行立马写进文件(不写的话,那么就会是周期性的同步)
7.}