UIPageViewController: get the currentPage

Question

I have been struggling with this issue for the last few days and after all this juggling I have figured out that all I need is the current Index from the datasource method to update with current visible page number

I have this UIPageViewController datasource method and I need to use the current index to get the current visible page for delegate method previousViewControllers transitionCompleted:(BOOL)completed

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
   viewControllerAfterViewController:(UIViewController *)viewController { 
    NSString *path = [[NSBundle mainBundle] pathForResource:@"pages" ofType:@"pdf"];

    NSURL *pdfurl = [NSURL fileURLWithPath:path];
    PDFDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfurl);

    contentViewController = [[ContentViewController alloc] initWithPDFAtPath:path];

    currentIndex = [modelArray indexOfObject:[(ContentViewController *)viewController page]];

    if (currentIndex == totalPages - 1) {  
        return nil;
    }

    contentViewController.page = [modelArray objectAtIndex:currentIndex + 1];

    return contentViewController;
}

I'm confused about how to write the current index statement from datasource method into delegate method to update current visible page.

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

    if (!completed)
    {
        return;
    }

    //currentIndex = [[self.pageViewController.viewController lastObject]];  
    currentIndex = [self indexOfObject:contentViewController];

    [self displaycurrentIndex:currentIndex];
    //self.pageControl.currentPage = currentIndex;
}

How can I correct this?

Answer 1

It looks like you should be able to get the current index with:

ContentViewController *viewController = [self.pageViewController.viewControllers lastObject];
currentIndex = [modelArray indexOfObject:[viewController page]];

Answer 2

for swift:

func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool){
        let pageContentViewController = pageViewController.viewControllers![0] as! ViewController
        let index = pageContentViewController.pageIndex

}

Answer 3

if you implement ModelController (as in Apple example), use it's method indexOfViewController

- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
    myDataViewController *currentView = [pageViewController.viewControllers objectAtIndex:0];
    NSInteger currentIndex = [_modelController indexOfViewController:currentView];
    [self displayPageNumber:currentIndex];
}

Answer 4

I am facing the same issue on pageViewController, everytime i swipe my pageViewController it calls my delegate twice and am not able to find the issue. And my array is dynamic so i want the proper index value from pageController. First of all set the delegate of your pageViewController. Like this :-

self.pageViewController.delegate = self;

And then add this delegate method to your class

- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
{
if (completed) {
    NSInteger currentIndex = ((PageContentViewController *)self.pageViewController.viewControllers.firstObject).pageIndex;

    NSLog(@"%ld",(long)currentIndex);
}
}

PageContentViewController is the class where you are showing your data of pageViewController.

Run your project and if everything is working fine, you will get your index value. PageIndex is the Integer value for getting the current index. Hope it will helps you.

Thanks

Mandeep Singh

Answer 5

My approach is quite simple:

1. When the page (controller) is instantiated I pass in the page index, which at this point is known.

2. Then in the delegate call below, iff the transition finished, I obtain the controller currently shown and cast it to my custom page class, before I fetch and update the currentPage with the associated page index.

To keep things simple I setup the data source and delegate to be the WalkThroughController which embeds the page view controller.

extension WalkThroughController: UIPageViewControllerDelegate {

    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {

        guard finished, let currentPageController = pageViewController.viewControllers?.last as? WalkThroughPageViewController else {
            return
        }

        self.currentPage = currentPageController.pageIndex
    }

}

The take away point is to set the page index of the pages when they are created in the data source. With this approach it is very straight forward to retrieve it later.