Line runs 3 times on load inside my scrollView - ios

Question

I have implemented a scrollView into my app..
It works fine except that when it first runs and I swipe the commands I posted below get called multiple times then the itemIndex is skipped ahead by 1, so none of my other code works.
class ViewController: UIViewController, UIPageViewControllerDataSource {
// MARK: - Variables
private var pageViewController: UIPageViewController?
// Initialize it right away here
private let contentImages = quizQuestion
// MARK: - View Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
createPageViewController()
setupPageControl()
}
private func createPageViewController() {
let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as! UIPageViewController
pageController.dataSource = self
if contentImages.count > 0 {
let firstController = getItemController(0)!
let startingViewControllers: NSArray = [firstController]
pageController.setViewControllers(startingViewControllers as [AnyObject], direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
}
pageViewController = pageController
addChildViewController(pageViewController!)
self.view.addSubview(pageViewController!.view)
pageViewController!.didMoveToParentViewController(self)
}
private func setupPageControl() {
let appearance = UIPageControl.appearance()
appearance.pageIndicatorTintColor = UIColor.grayColor()
appearance.currentPageIndicatorTintColor = UIColor.whiteColor()
appearance.backgroundColor = UIColor.darkGrayColor()
}
// MARK: - UIPageViewControllerDataSource
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
let itemController = viewController as! PageItemController
var index = itemController.itemIndex
if index == 0 || index == NSNotFound {
index = self.contentImages.count
}
index--
return getItemController(index)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
let itemController = viewController as! PageItemController
var index = itemController.itemIndex
if index == NSNotFound {
return nil
}
index++
if index == self.contentImages.count {
index = 0
}
return getItemController(index)
}
private func getItemController(itemIndex: Int) -> PageItemController? {
if itemIndex < contentImages.count {
let pageItemController = self.storyboard!.instantiateViewControllerWithIdentifier("ItemController") as! PageItemController
// as you can see, everything is working fine
// 1 to 2, 2 to 3 etc.
// what you see here is your default PageViewController behaviour. When we scroll from view 1 to view 2, pageViewcontroller will automatically call 2 methods:viewControllerAfterViewController and viewControllerBeforeViewController
// if you want to get current index, let me think, you can get it here.
// are you clear now?
pageItemController.itemIndex = itemIndex
// pageItemController.imageName = contentImages[itemIndex]
//println(contentImages[itemIndex])
//println("item index is \(contentImages[itemIndex])")
return pageItemController
}
return nil
}
}
This is the code that gets repeated when ever I swipe when the page first loads.
// MARK: - View Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
println("item index is \(itemIndex)") <-
questionLabel.text = quizQuestion[itemIndex].question <-
println(quizQuestion[itemIndex].question) <-
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
}
The following image shows the index working correctly when the view first loads.
Now I have swiped left once and the index should be 1 but not only is it not 1 it has loaded the view atleast 3 more times

Answer 1

There is no guarantee that the UIPageViewCOntroller subsystem won't generate the view controller for the next view, and the view after that ahead of time. My guess is that is what is happening. You may want to keep track of the view controllers yourself. You could keep an array of PageItemController objects. You could then check the itemIndex of the viewController passed in to pageViewController(pageViewController:viewControllerAfterViewController:) and generate the next, or return the correct one from the array. But you may not need to or want to do that.