ios5 - 有条件地从 AppDelegate 加载故事板文件和第一个场景

Question

我最近将我的应用程序转换为通用二进制文件，并将现有的情节提要复制到 iPad 格式。我的印象是我可以有条件地从该方法加载情节提要文件，

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

我在上述方法中有以下代码，但我的初始场景没有从情节提要文件中加载。我得到一个没有任何内容的白屏，但​​我确实看到了状态栏。

// iPad Legacy 1024 x 768
    if([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad) {
        // the iOS device is in the iPad family.


        NSLog(@"the iOS device = %@",[UIDevice currentDevice]);

        CGSize iOSDeviceScreenSize = [[UIScreen mainScreen] bounds].size;

        NSLog(@"The size of screen is %f",iOSDeviceScreenSize.height);

            if (iOSDeviceScreenSize.height == 1024) {

                // load storyboard , load rootviewcontroller, show initial scene

                UIStoryboard *sbipad = [UIStoryboard storyboardWithName:@"iPad" bundle:nil];

                ViewControllerWelcome *vcwelcome = [sbipad instantiateInitialViewController];

                self.window.rootViewController = vcwelcome;

                [self.window makeKeyAndVisible];

                NSLog(@"iPad storyboard file loaded");
            }
    }

    if([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPhone) {

        CGSize iOSDeviceScreenSize = [[UIScreen mainScreen] bounds].size;

            if (iOSDeviceScreenSize.height == 480) {

                // iphone 3GS, 4, 4S, and iPod Touch 3rd and 4th gen 3.5 inch screen diagnolly measured

                UIStoryboard *sbiphone = [UIStoryboard storyboardWithName:@"iPhone" bundle:nil];

                ViewControllerWelcome *vcwelcome = [sbiphone instantiateInitialViewController];

                self.window.rootViewController = vcwelcome;

                [self.window makeKeyAndVisible];

                NSLog(@"iPhone storyboard file loaded");
            }

            if (iOSDeviceScreenSize.height == 568) {

                // iphone 5 and ipod touch 5th gen: 4 inch screen diagnolly measured

                UIStoryboard *sbiphone = [UIStoryboard storyboardWithName:@"iPhone" bundle:nil];

                ViewControllerWelcome *vcwelcome = [sbiphone instantiateInitialViewController];

                self.window.rootViewController = vcwelcome;

                [self.window makeKeyAndVisible];

                NSLog(@"iPhone storyboard file loaded for iPhone 5 (4inch screen)");
            }
    }

    return YES;