gimenete

// put this 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;