UIPageViewController transition 'Unbalanced calls to begin/end appearance transitions for '

Question

When I navigate through UIPageViewController faster than its transition animation I am getting \'Unbalanced calls to begin/end appearance transitions for <

Answer 1

Here's a QUICK version using the delegate:

add this code (make sure you're including the UIPageViewControllerDelegate in your header or class extension, and assign self.pageViewController.delegate = self;):

- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers {
   self.pageAnimationFinished = NO;
}

- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
    self.pageAnimationFinished = YES;
}

then check self.pageAnimationFinished and return nil if it's == NO.

Longer Explanation:

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

We can use this delegate method from UIPageViewControllerDelegate to know when the animation from flipping or swiping through pages finishes. Using this we just can implement it like this:

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

then, just return nil in your

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(PageViewController *)viewController

and

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(PageViewController *)viewController

when

pageAnimationFinished == NO. Be sure to set pageAnimationFinished to NO when you animate. The best way to know when you animate is by using the opposite of

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

namely:

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

I haven't seen that warning ever since and this can be done in 1/3 of the lines as the other solutions. And it's MUCH easier to follow.