用繼承自UINavigationController與UITabbarController 創建類，將前者設置為RootViewController,出現了一個問題，navigetionController的title不顯示，在controller里面怎么設置都不顯示，原因是這個樣子的：
title這個屬性實際上是屬於UIViewController而不屬於UINavigationController。所以，這個屬性是從UIViewController上面繼承過來的。而不是UINavigationController上面的名字。由於UINavigationController屬於容器，所以最少需要一個RootController。然后在RootController的viewDidLoad設置title而不是在UINavigationController的subclass中設置。而且viewDidLoad設置的title是統一顯示的，導航視圖控制的UIViewController的title都是一樣的，我的解決方法是：將邏輯更換，UITabbarController設置為RootViewController，
1 -(void)addTage:(Class)controller addName:(NSString *)name addImage:(NSString *)image addSelectImage:(NSString *)selectImage 2 3 { 4 5 6 7 UIViewController *vc = [[controller alloc] init]; 8 9 UINavigationController *cityNav = [[UINavigationControlleralloc]initWithRootViewController:vc]; 10 11 cityNav.tabBarItem.image = [UIImage imageNamed:image]; 12 13 cityNav.tabBarItem.selectedImage = [UIImage imageNamed:selectImage]; 14 15 cityNav.navigationBar.backgroundColor = [UIColor blueColor]; 16 17 cityNav.tabBarItem.title = name; 18 19 cityNav.navigationBar.barStyle = UIBarStyleDefault; 20 21 cityNav.navigationBar.barTintColor = [UIColor cyanColor]; 22 23 [self.navArray addObject:cityNav]; 24 25 26 27 } 28 29 30 31 self.tabBarController.viewControllers = self.navArray; 32 33 34 self.window.rootViewController = self.tabBarController;
self.navigationItem.title
= @"my title"; sets navigation bar title.
self.tabBarItem.title
= @"my title"; sets tab bar title.
self.title
= @"my title"; sets both of these.