UIPageViewController完成块未调用

Question

当我打电话

- (void)setViewControllers:(NSArray *)viewControllers 
                 direction:(UIPageViewControllerNavigationDirection)direction 
                  animated:(BOOL)animated 
                completion:(void (^)(BOOL finished))completion;

{p} UIPageViewController delegate

中的

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

我看到没有调用完成块。但是当我在delegate方法之外调用此方法时，将调用完成块。 我配错了吗？你能给我一些暗示吗？

谢谢！