Child View Controller shifts down

Question

I have a TutorialsViewController that has a PageViewController added programmatically as:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    // Create page view controller
    self.pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"TutorialsPageViewController"];
    self.pageViewController.dataSource = self;

    TutorialsContentViewController *startingViewController = [self viewControllerAtIndex:0];

    NSArray *viewControllers = @[startingViewController];
    [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:nil];

    [self addChildViewController:self.pageViewController];
    [self.view addSubview:self.pageViewController.view];
    [self.pageViewController didMoveToParentViewController:self]; 
}

And I add TutorialsContentViewController to the PageViewController using the delegate methods:

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
    NSUInteger index = ((TutorialsContentViewController*) viewController).pageIndex;

    if ((index == 0) || (index == NSNotFound)) {
        return nil;
    }

    index--;
    return [self viewControllerAtIndex:index];
}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
    NSUInteger index = ((TutorialsContentViewController*) viewController).pageIndex;

    if (index == NSNotFound) {
        return nil;
    }

    index++;
    if (index == [self.tutorialsArray count]) {
        return nil;
    }
    return [self viewControllerAtIndex:index];
}

- (TutorialsContentViewController *)viewControllerAtIndex:(NSUInteger)index {
    if (([self.tutorialsArray count] == 0) || (index >= [self.tutorialsArray count])) {
        return nil;
    }

    // Create a new view controller and pass suitable data.
    TutorialsContentViewController *tutorialsContentViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"TutorialsContentViewController"];
    tutorialsContentViewController.imageName = [self.tutorialsArray objectAtIndex:index];
    tutorialsContentViewController.pageIndex = index;
    return tutorialsContentViewController;
}

Now when i run this in simulator, i can see everything working fine, just that the next child view controller appears to be above the status bar and it shifts down as I scroll.

I have tried self.automaticallyAdjustsScrollViewInsets = false in the Parent View Controller but the child view still shifts down. The child view controller has an ImageView that has leading, trailing, top, bottom constraints set to 0 initially (this causes the shift).

When i centre the image horizontally and vertically and give it fixed height and width, it works fine though. But i want the image to completely fill the child view controller.

How to solve this view shifting problem? Please help.

Thanks.

Answer 1

I seem to have found the fix for it, it was related to the auto layout constraints i had set up. My child view controller contains an image view that completely fills it. So i give following constraints to the image view:

1. Center Horizontally In Container
2. Center Vertically In Container
3. Equal Widths (to the container view)
4. Equal Heights (to the container view)

This stops the view shifting/flickering problem.