- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {                // 1. 创建窗口    self.window = [[UIWindow alloc] init];    self.window.frame = [UIScreen mainScreen].bounds;        // 2. 设置根控制器    UITabBarController *tabbarVc = [[UITabBarController alloc] init];    self.window.rootViewController = tabbarVc;            // 3. 设置子控制器属性    DJHomeViewController *homeVc = [[DJHomeViewController alloc] init];    [self setChildVc:homeVc withTitle:@"首页" image:@"tabbar_home" selectedImage:@"tabbar_home_selected"];        DJMessageCenterViewController *messageCenterVc = [[DJMessageCenterViewController alloc] init];    [self setChildVc:messageCenterVc withTitle:@"消息" image:@"tabbar_message_center" selectedImage:@"tabbar_message_center_selected"];        DJDiscoverViewController *discoverVc = [[DJDiscoverViewController alloc] init];    [self setChildVc:discoverVc withTitle:@"发现" image:@"tabbar_discover" selectedImage:@"tabbar_discover_selected"];        DJProfileViewController *profileVc = [[DJProfileViewController alloc] init];    [self setChildVc:profileVc withTitle:@"我" image:@"tabbar_profile" selectedImage:@"tabbar_profile_selected"];        // 4. 添加子控制器    [tabbarVc addChildViewController:homeVc];    [tabbarVc addChildViewController:messageCenterVc];    [tabbarVc addChildViewController:discoverVc];    [tabbarVc addChildViewController:profileVc];            // 5. 显示窗口    [self.window makeKeyAndVisible];    return YES;}- (void)setChildVc:(UIViewController *)vc withTitle:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage {    vc.view.backgroundColor = DJRandomColor;    vc.tabBarItem.title = title;        // 设置tabbarItem 选中图片    vc.tabBarItem.image = [UIImage imageNamed:image];    vc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];        // 设置tabarItem 选中颜色    NSMutableDictionary *textAttrs = [NSMutableDictionary dictionary];    textAttrs[NSForegroundColorAttributeName] = DJColor(123, 123, 123);        NSMutableDictionary *selectedTextAttrs = [NSMutableDictionary dictionary];    selectedTextAttrs[NSForegroundColorAttributeName] = [UIColor orangeColor];            [vc.tabBarItem setTitleTextAttributes:textAttrs forState:UIControlStateNormal];    [vc.tabBarItem setTitleTextAttributes:selectedTextAttrs forState:UIControlStateSelected];}