如何在PageViewController中将CGGradients融合在一起？

Question

I have a UIPageViewController with 4 pages, by taking the sample from here: http://www.appcoda.com/uipageviewcontroller-storyboard-tutorial/ and removing the set images and adding in custom gradients for each view. Let's say that page 1 is red/yellow, page 2 is yellow/blue, etc, so what I want is when the transition happens between page 1 and 2, instead of seeing a solid line between the two gradient views, as such:

I'd like to be able to blend the transition and make it look nice. I have found the delegate methods for the PageViewController as likely the place that I need to execute this custom behavior:

- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers {
}

- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
}

From these methods, how could I basically remove the separator line and blend over it with my own custom colors? Would I be creating another UIView on top of the existing set of views and animate that?

Answer 1

The problem is that with a UIPageViewController you are not in charge of the views and (even more important) you don't get to customize the transition animation, so you can't add anything at the join.

Since you only have four views, I would suggest you abandon UIPageViewController entirely and use instead a paging UIScrollView. This gives you the same behavior - the user can scroll from "page" to "page" - but now you are in complete control of everything inside the UIScrollView's content and can modify / overlay as you see fit. Use the delegate methods to learn when the user is scrolling and when the user has finished.