UITabBarController（标签栏控制器）

self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];    self.window.backgroundColor = [UIColor whiteColor];    [self.window makeKeyAndVisible];    RootViewController *rootCtrl = [[RootViewController alloc] init];    //创建导航控制器    UINavigationController *navCtrl = [[UINavigationController alloc] initWithRootViewController:rootCtrl];    navCtrl.title = @"首页";    //创建视图    UIViewController *vc1 = [[UIViewController alloc] init];    vc1.title = @"收藏";    UIViewController *vc2 = [[UIViewController alloc] init];    vc2.title = @"搜索";    UIViewController *vc3 = [[UIViewController alloc] init];    vc3.title = @"设置";    NSArray *controllers = [NSArray arrayWithObjects:navCtrl,vc1,vc2,vc3,nil];        //创建标签栏控制器的实例    UITabBarController *tabCtrl = [[UITabBarController alloc] init];        //将存有视图控制器实例的数组赋给tabCtrl    tabCtrl.viewControllers = controllers;    //默认选择第2个视图选项卡（索引从0开始的）    tabCtrl.selectedIndex = 1;    //把tabBarController的view作为子视图添加到window    self.window.rootViewController = tabCtrl;