Refresh UIPageViewController - reorder pages and add new pages

Question

I have a UIPageViewController which I am providing page data for using an implementation of UIPageControllerDelegate and UIPageControllerDataSource.

It's all working fine, but I want to be able to add items to the page data and reorder the page data.

If a user has already got to the last of the pages, and then I add an item, they can't get to the next page because viewControllerAfterViewController: has already been called. If they scroll back one and then forward two they can get to the new page fine, so the data is setup correctly. How can I tell the UIPageViewController to refresh its store of what comes next?

Similarly I would like to reorder the collection that is backing the page view. But if I do this I'll get the same problem - the page view will think the next page is still what it was last time the current page was loaded.

I guess I'm looking for something similar to reloadData: on UITableView.

Answer 1

I found a workaround to force UIPageViewController to forget about cached view controllers of neighboring pages that are currently not displayed:

pageViewController.dataSource = nil;
pageViewController.dataSource = self;

I do this everytime I change the set of pages. Of course this doesn't affect the currently displayed page.

With this workaround I avoid the caching bug and can still use animated:YES in setViewControllers:direction:animated:completion:.

Answer 2

You need to call setViewControllers:direction:animated:completion:.

Also, in iOS 6, watch out if you're using UIPageViewControllerTransitionStyleScroll style, as there is a major caching bug if animated: is YES (see my discussion here: UIPageViewController navigates to wrong page with Scroll transition style).

Answer 3

Here's my complete implementation of @ortwin-gentz's answer in the didFinish delegate method in Swift 2, which works perfectly for me:

func pageViewController(
    pageViewController: UIPageViewController,
    didFinishAnimating finished: Bool,
    previousViewControllers: [UIViewController],
    transitionCompleted completed: Bool
) {
    if !completed { return }
    dispatch_async(dispatch_get_main_queue()) {
        pageViewController.dataSource = nil
        pageViewController.dataSource = self
    }
}