Two-stage rotation animation is deprecated. This application should use the smoother single-stage an

问题出在rootViewController同时包含UITabBarController和UINavigationController。

几经尝试，最后发现，在设置为window.rootViewController之前，先指定tabBarController.selectedIndex = 0，问题解决。

可以得出，出现上述错误，是因为XCode不知道你需要push哪个子viewController，在加载navigationController的时候，不知道要载入哪一个controller，于是无脑的将tabBarController的viewControllers都动画载入了。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.backgroundColor = [UIColor whiteColor];

    

    UIStoryboard *pStoryBoard = [UIStoryboard storyboardWithName:@"FirstStoryBoard" bundle:nil];

    UINavigationController *pNavigationController = [pStoryBoard instantiateInitialViewController];

    UITabBarController *pTabBarController = (UITabBarController *)pNavigationController.visibleViewController;

    pTabBarController.selectedIndex = 0; /// 就是这句话

    [UIApplication sharedApplication].delegate.window.rootViewController = pNavigationController; /// 这句话在其他VC也可以用

    [self.window makeKeyAndVisible];

    return YES;

}