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.

Solution 1

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).

Solution 2

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:.

Solution 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
    }
}

Solution 4

Swift 4 Version for reload of data of pageviewcontroller, to @theory's version.

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

View more solutions

Comments

[ssloan]

Thanks - the setViewControllers:direction:animated:completion: did it. Cheers for mentioning the bug too.

[ernesto]

Interesting. Where do you unset and reset the dataSource? Before setViewControllers:direction:animated:completion:, after it, or in the completion block? Thanks.

[Ortwin Gentz]

Actually, I do this 0.01 seconds after didFinish in a dispatch_async block.

[Michael McGuire]

Thank you! This method works when using a data source. The accepted answer didn't work for me, at least on iOS 8. Using "setViewControllers:direction:animated:completion:" with the current view controller did not cause the data source to be called again.

[Alex Sfinx87]

Thx for this solution. :-)

[Mr.Fingers]

tip: After you reset dataSource (a.k.a. pageViewController.dataSource = nil;) your method -viewControllerBefore and -viewControllerAfter will be called again. For restore the dataSource.

[Ozgur Vatansever]

You need to reassign dataSource like above if presentationCountForPageViewController returns a dynamic value which might change after the refresh.

[BaseZen]

Double plus good. Why this is not documented -- inexcusable. Confirmed for iOS 10, Swift 2.3, Xcode 8

[Kartick Vaddadi]

This doesn't work, at least not in iOS 10.3. The crash happens in setViewControllers(), so doing something 0.01 seconds afterward is too late. I tried this trick before calling setViewControllers(), and it doesn't work.

[Gon]

doesn't work iOS 10 when you call setViewControllers:direction:animated:completion: fast enough, still got wrong content offset.

[Uday Kumar Eega]

Worked like charm...Perfect..Thanks

[DJTano]

And what if I also want to update the currently displayed page ?

[Ortwin Gentz]

@DJTano that's the purpose of setViewControllers:direction:animated:completion:. Even though it asks for an array of view controllers, you usually send a single array (exception is a 2-element array if spineLocation = .mid) with the current VC.

[DJTano]

@OrtwinGentz got it. Thanks!! :)