objective c - iOS Present modal view controller on startup without flash

Question

I'd like to present modally, at first startup, a tutorial wizard to the user.

Is there a way to present a modal UIViewController on application startup, without seeing, at least for a millisecond, the rootViewController behind it?

Now I'm doing something like this (omitting first-launch checks for clarity):

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

    // ...

    UIStoryboard *storyboard = self.window.rootViewController.storyboard;
    TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
    tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    [self.window makeKeyAndVisible];
    [self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:NULL];
}

with no luck. I've tried to move [self.window makeKeyAndVisible]; to before the [... presentViewController:tutorialViewController ...] statement, but then the modal doesn't even appear.

Answer 1

All presentViewController methods require the presenting view controller to have appeared first. In order to hide the root VC an overlay must be presented. The Launch Screen can continued to be presented on the window until the presentation has completed and then fadeout the overlay.

    UIView* overlayView = [[[UINib nibWithNibName:@"LaunchScreen" bundle:nil] instantiateWithOwner:nil options:nil] firstObject];
overlayView.frame = self.window.rootViewController.view.bounds;
overlayView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self.window makeKeyAndVisible];
[self.window addSubview:overlayView];
[self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:^{
    NSLog(@"displaying");
    [UIView animateWithDuration:0.5 animations:^{
        overlayView.alpha = 0;
    } completion:^(BOOL finished) {
        [overlayView removeFromSuperview];
    }];
}];