UIPageViewController transition PageCurl with UIScrollView wrong page index - ios

Question

I have searched a lot before posting without success:
I have UIPageViewController with array of UIViewController and PageCurl as transition.
Every UIViewController consists of UIScrollView and UIWebView.
the scroll height calculated based on webview height after loading the content.
now when I load UIPageViewController and start navigation between UIViewController without scrolling the content every thing works fine. But if I scrolled any page and then navigate to the next page or previous one. it will redisplay the same page and then works again normally.
I have tested it on IOS7 and IOS8:
UIPageViewController viewDidLoad method:
self.pageController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
NSArray *viewControllers = [NSArray arrayWithObject:currentViewController];
[self.pageController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
self.pageController.doubleSided = NO;
[self addChildViewController:self.pageController];
[[self view] addSubview:[self.pageController view]];
[self.pageController didMoveToParentViewController:self];
View Controller webViewDidFinishLoad:
CGSize contentSize = aWebView.scrollView.contentSize;
webView.frame = CGRectMake(0, 312, contentSize.width, contentSize.height);
scrollView.contentSize = CGSizeMake(320.f, contentSize.height+60);
Edit
Here is the complete code for viewControllerBeforeViewController and viewControllerAfterViewController of UIPageViewController
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
NSUInteger index = [(NewsDetailVC *)viewController index];
self.index = index;
NSLog(#"view before %i", index);
if (index <= 0) {
return nil;
}
index--;
currentViewController = [self viewControllerAtIndex:index];
return [self viewControllerAtIndex:index];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
NSUInteger index = [(NewsDetailVC *)viewController index];
NSLog(#"view after %i", index);
if (index >= self.newsList.count -1) {
return nil;
}
index++;
currentViewController =[self viewControllerAtIndex:index];
return [self viewControllerAtIndex:index];
}
Edit2
The previous page is an UIViewController contains UITableView when click on a cell will pass the array of Items to UIPageViewController and the selected index.
The purpose of currentViewController because I have controls for font size, and current view background.
The UIPageViewController parent is UIViewController
Here is the code of viewControllerAtIndex:
- (NewsDetailVC *)viewControllerAtIndex:(NSUInteger)index {
NewsDetailVC *childViewController = [[UIStoryboard storyboardWithName:#"Main_iPhone" bundle:nil] instantiateViewControllerWithIdentifier:#"NewsDetailVC"];
childViewController.index = index;
childViewController.selectedNews = [self.newsList objectAtIndex:index ];
childViewController.selectedCategory = self.selectedCategory;
return childViewController;
}

Answer 1

I had the same problem with an UIPageViewController.
It seems like the index shown in viewControllerAtIndex is not quite an accurate one.
As somebody else mentioned in the comment above, in these situations you should implement the delegate method pageViewController:willTransitionToViewControllers.
In this method you should do your work:
- (void)pageViewController:(UIPageViewController *)pageViewController
willTransitionToViewControllers:(NSArray *)pendingViewControllers {
if ([pendingViewControllers count] > 0) {
NSUInteger index = [(PageContentViewController *)
[pendingViewControllers objectAtIndex:0] pageIndex];
if (index == [yourArray count] - 1 || index == 0) {
[self loadContent];
} else {
[self doOtherStuff];
}
}
}
Somehow, the * viewControllerAtIndex* is called several times, giving you troubles finding the index, but in this method the index should be accurate.
Hope it helps!