View keeps empty after opened through an alert - ios

Question

there's an alert in my app and when the user clicks on its ok-button an new few opens: But this few keeps empty...no buttons, etc. are shown (somehow the background is correctly shown).
This alert opens at first launch of the app in AppDelegate.m file:
-(void) alertView:(UIAlertView *) alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
if (buttonIndex == 0) {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
FirstVC *launchViewController = [[FirstVC alloc] init];
self.window.rootViewController = launchViewController;
[self.window makeKeyAndVisible];
}
}
Maybe it's wrong to use UIWindow.
Thanks to all of your answers. (FirstVC is the viewController shown after the alert-buttton is clicked)
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
if (! [defaults boolForKey:#"notFL"]) {
UIAlertView *alert = [[UIAlertView alloc]initWithTitle: #"Welcome"
message: #"..."
delegate: self
cancelButtonTitle:nil
otherButtonTitles:#"OK",nil];
[alert show];
[defaults setBool:YES forKey:#"notFL"];
}
}

Answer 1

You need to describe what controllers you have in the storyboard. What controller is the alert shown over when the app first opens? Your problem is that you're just alloc init'ing a FirstVC, not getting the one you set up in the storyboard. To get that instance, you need to do something like this:
FirstVC *launchViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"FirstVC"];
This will work if you call it from the initial view controller that the alert is shown over. I think it would be better to put the coed you posted in the viewDidAppear method of that first controller.
If you want to do this in the app delegate, then you need to get a reference to the storyboard in a different way:
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:#"MainStoryboard" bundle:nil];
FirstVC *launchViewController = [storyboard instantiateViewControllerWithIdentifier:#"FirstVC"];