- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{     self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];    //初始化 tabBarItem对应的ViewController    UIViewController *viewCtrl1 = [[UIViewController alloc] init];    viewCtrl1.title = @"first viewctrl";    viewCtrl1.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"rename first" image:nil tag:1];//自己定义tabBarItem是在对应的ViewController中去做    viewCtrl1.view.backgroundColor = [UIColor blueColor];        UIViewController *viewCtrl2 = [[UIViewController alloc] init];    viewCtrl2.title = @"second viewctrl";    viewCtrl2.view.backgroundColor = [UIColor yellowColor];    viewCtrl2.tabBarItem.badgeValue = @"360";        UIViewController *viewCtrl3 = [[UIViewController alloc] init];    viewCtrl3.title = @"3 viewctrl";    viewCtrl3.view.backgroundColor = [UIColor colorWithRed:0.1 green:0.2 blue:0.3 alpha:1.0];        UIViewController *viewCtrl4 = [[UIViewController alloc] init];    viewCtrl4.title = @"4 viewctrl";    viewCtrl4.view.backgroundColor = [UIColor colorWithRed:0.1 green:0.5 blue:0.3 alpha:1.0];        UIViewController *viewCtrl5 = [[UIViewController alloc] init];    viewCtrl5.title = @"5 viewctrl";    viewCtrl5.view.backgroundColor = [UIColor colorWithRed:0.1 green:0.5 blue:0.7 alpha:1.0];        UIViewController *viewCtrl6 = [[UIViewController alloc] init];    viewCtrl6.title = @"6 viewctrl";    viewCtrl6.view.backgroundColor = [UIColor colorWithRed:0.6 green:0.5 blue:0.7 alpha:1.0];        UIViewController *viewCtrl7 = [[UIViewController alloc] init];    viewCtrl7.title = @"7 viewctrl";    viewCtrl7.view.backgroundColor = [UIColor colorWithRed:0.9 green:0.5 blue:0.3 alpha:1.0];        //    tabBarCtrl = [[UITabBarController alloc] init];    tabBarCtrl.viewControllers = [NSArray arrayWithObjects:viewCtrl1, viewCtrl2 ,viewCtrl5,  viewCtrl3, viewCtrl4, viewCtrl6, viewCtrl7, nil];//添加viewcontrollers, 数组顺序就是tabBarItem对应的viewController顺序 tabBarCtrl.customizableViewControllers = [NSArray arrayWithObjects: viewCtrl2 ,viewCtrl3, viewCtrl5, viewCtrl7, nil]; //显示可编辑的有那些viewcontroller  [tabBarCtrl  setSelectedIndex: 3];//设置选中的是那个tabBarItem,如果为无效的index,则默认选中第一个tabBarCtrl.view.frame = CGRectMake(0, 0, self.window.frame.size.width, self.window.frame.size.height); self.window.rootViewController = tabBarCtrl; [self.window makeKeyAndVisible]; return YES; } 关于旋转UITabBarController默认只支持竖屏，当设备方向放生变化时候，它会查询viewControllers中包含的所有ViewController，仅当所有的viewController都支持该方向时，UITabBarController才会发生旋转，否则默认的竖向。UITabBarController支持旋转，而且发生旋转的时候，只有当前显示的viewController会接收到旋转的消息。 关于 UITabBarControllerDelegate 委托//设置用户是否可以选中，如果返回NO,用户不能选中，但代码中还可以用tabBarCtrl  setSelectedIndex: 3]选中- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController；{　　　　return YES;}//选中后的消息响应- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{} more 中edit监测- (void)tabBarController:(UITabBarController *)tabBarController willBeginCustomizingViewControllers:(NSArray *)viewControllers;- (void)tabBarController:(UITabBarController *)tabBarController willEndCustomizingViewControllers:(NSArray *)viewControllers changed:(BOOL)changed;- (void)tabBarController:(UITabBarController *)tabBarController didEndCustomizingViewControllers:(NSArray *)viewControllers changed:(BOOL)changed;