RootViewController Switch Transition Animation

Is there any way to have a Transition/animation effect while replacing an existing viewcontroller as rootviewcontroller with a new one in the appDelegate?

You can wrap the switching of the rootViewController in a transition animation block:

[UIView transitionWithView:self.window
                  duration:0.5
                   options:UIViewAnimationOptionTransitionFlipFromLeft
                animations:^{ self.window.rootViewController = newViewController; }
                completion:nil];

I found this and works perfectly:

in your appDelegate:

- (void)changeRootViewController:(UIViewController*)viewController {

    if (!self.window.rootViewController) {
        self.window.rootViewController = viewController;
        return;
    }

    UIView *snapShot = [self.window snapshotViewAfterScreenUpdates:YES];

    [viewController.view addSubview:snapShot];

    self.window.rootViewController = viewController;

    [UIView animateWithDuration:0.5 animations:^{
        snapShot.layer.opacity = 0;
        snapShot.layer.transform = CATransform3DMakeScale(1.5, 1.5, 1.5);
    } completion:^(BOOL finished) {
        [snapShot removeFromSuperview];
    }];
}

in your app

 if (!app) { app = (AppDelegate *)[[UIApplication sharedApplication] delegate]; }
        [app changeRootViewController:newViewController];

credits:

https://gist.github.com/gimenete/53704124583b5df3b407