一、介绍
如今iOS开发过程中，最常见的一种UI架构是：界面底部是四五个tab bar 、中间是内容显示、顶部是包括标题及返回等操作button，当点击进入某个模块后可以点击进行返回。这样的架构的应用比較常见的如：微信、支付宝、京东、去哪儿等大部分应用都是这样的UI架构。下图所看到的：
二、创建方法
iOS开发SDK中提供了比較方便的类：UITabBarController、UINavigationController、UIViewController组合起来进行实现。通常在 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 。应用生命周期方法中完毕主UI架构的创建。
详细步骤为 ：1、新建与tab bar个数一致的UIViewController 实例，初始化title，button等。
2、新建与tab bar个数一致UINavigationController实例，通过调用initWithRootViewController 分别赋给响应的UIViewController实例。 3、新建一个UITabBarController实例变量，然后给UITabBarController的viewControllers数组赋值为上面新建的多个UINavigationController实例。
4、把AppDelegate中的window属性的 rootViewController 设置为一个UITabBarController实例变量， 5、然后调用[self.window makeKeyAndVisible]方法显示界面。
三、详细实现代码
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds]]; self.window.backgroundColor= [UIColor redColor]; [self loadMainFrame]; [self.window makeKeyAndVisible]; return YES;}详细的实现位于loadMainFrame方法中-(void)loadMainFrame{ LOneViewController *oneController = [[LOneViewController alloc]init]; UINavigationController *onNav = [[UINavigationController alloc]initWithRootViewController:oneController]; oneController.tabBarItem.title=@"First"; oneController.tabBarItem.image = [UIImage imageNamed:@"one.png"]; LOneViewController *twoController = [[LOneViewController alloc]init]; UINavigationController *twoNav = [[UINavigationController alloc]initWithRootViewController:oneController]; twoController.tabBarItem.title=@"First"; twoController.tabBarItem.image = [UIImage imageNamed:@"one.png"]; LThreeViewController *threeController = [[LThreeViewController alloc]init]; UINavigationController *threeNav = [[UINavigationController alloc]initWithRootViewController:threeController]; threeNav.tabBarItem.title=@"Three"; threeNav.tabBarItem.image=[UIImage imageNamed:@"three.png"]; LFourViewController *fourController = [[LFourViewController alloc]init]; UINavigationController *fourNav = [[UINavigationController alloc]initWithRootViewController:fourController]; fourNav.tabBarItem.title=@"Four"; fourNav.tabBarItem.image=[UIImage imageNamed:@"four.png"]; fourNav.navigationBar.tintColor=[UIColor yellowColor]; LFiveViewController *fiveController = [[LFiveViewController alloc]init]; UINavigationController *fiveNav = [[UINavigationController alloc]initWithRootViewController:fiveController]; fiveNav.navigationBar.tintColor=[UIColor yellowColor]; fiveNav.tabBarItem.title=@"Five"; fiveNav.tabBarItem.image=[UIImage imageNamed:@"five.png"]; UITabBarController *tabController=[[UITabBarController alloc]init]; [tabController setViewControllers:@[onNav,twoNav,threeNav,fourNav,fiveNav] ]; self.window.rootViewController = tabController;}如上面代码所看到的：新建了四个UIViewController、以及四个UINavigationController，并把四个UIViewController设置为对应UINavigationController的rootViewController，然后把四个UINavigationController分别增加到UITabBarController的ViewControllers数组中。 然后设置 self.window.rootViewController为UITabBarController，最后 通过[self.window makeKeyAndVisible];方法完毕UI架构的创建。