I have an Assertion Failure in UIPageViewController.
Assertion failure in -[UIPageViewController _flushViewController:animated:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3512.60.12/UIPageViewController.m
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason:
'Don't know about flushed view <UIView: 0x15a5bff30; frame = (0 0; 768 903); autoresize = W+H; layer = <CALayer: 0x15a5bfc30>>'
*** First throw call stack:
(0x181ebedb0 0x181523f80 0x181ebec80 0x182844154 0x1877a1c40 0x1877a1da8 0x18784e9c4 0x18784ebfc 0x187852318 0x18784dd98 0x1870101e4 0x1849a2994 0x18499d5d0 0x1870270a4 0x10028b620 0x100348b78 0x100379f54 0x100168878 0x18733d568 0x1870330b4 0x1870f1a00 0x18733e71c 0x1870f832c 0x18703536c 0x18700f7ac 0x18700ed40 0x18700eba8 0x1873283b4 0x18700d5e8 0x18784ebd4 0x187852318 0x18784df3c 0x1871db550 0x1871daf6c 0x101c9b768 0x1849f0234 0x1849f00e8 0x182135e54 0x181e5d030 0x181e757d4 0x181e74f0c 0x181e72c64 0x181d9cc50 0x183684088 0x18707e088 0x10033b200 0x18193a8b8)
libc++abi.dylib: terminating with uncaught exception of type NSException
I don't know why this error is occurring. Any clues on what's causing it or how to debug it?
The direct way to run into this assert is to use cycled source for UIPageController defined with scroll transition style.
When the source contains two pages each one is the previous and the next for another one. If you swipe UIPageController containing two pages and then try to set source with 3 pages you will get the assertion mentioned above with guarantee assuming that UIPageControllerDataSource before/after methods allow cycled transition in case of 2 pages.
The main rules of crash-free using UIPageController with scroll transition:
1) set dataSource before calling setViewControllers method
2) use setViewControllers method without animation (animated: false)
3) set dataSource to nil for single page mode
4) don't allow cycles for 2-page mode
All these recommendations together make UIPageController absolutely stable.
import UIKit
/// Convenient subclass of UIPageViewController
#objc class AMPageViewController: UIPageViewController {
/// Turn on/off PageControl at the bottom
#objc var showPageControl: Bool = true
/// Array of all viewControllers
#objc var source: [UIViewController]? {
didSet {
let count = source?.count ?? 0
if count > 0 {
dataSource = count > 1 ? self : nil
}
else {
dataSource = nil
delegate = nil
}
}
}
/// Index of the current viewController from source
#objc var pageIndex: Int {
get {
var currentPageIndex: Int = 0
if let vc = viewControllers?.first, let source = source, let pageIndex = source.index(of: vc) {
currentPageIndex = pageIndex
}
return currentPageIndex
}
set {
guard newValue >= 0, let source = source, newValue < source.count else { return }
let vc = source[newValue]
let direction: UIPageViewControllerNavigationDirection = newValue < pageIndex ? .reverse : .forward
setViewController(vc, direction: direction)
}
}
override weak var delegate: UIPageViewControllerDelegate? {
get { return super.delegate }
set {
if source?.count ?? 0 > 0 {
super.delegate = newValue
}
else {
super.delegate = nil
}
}
}
/// Initializer in scroll-mode with interPageSpacing
#objc init(navigationOrientation: UIPageViewControllerNavigationOrientation = .horizontal, interPageSpacing: Int = 0) {
let options = (interPageSpacing > 0) ? [UIPageViewControllerOptionInterPageSpacingKey : 5] : nil
super.init(transitionStyle: .scroll, navigationOrientation: navigationOrientation, options: options)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
/// Set viewcontroller by index from source
#objc func setPageIndex(_ index: Int, completion: ((Bool) -> Void)? = nil) {
guard index > 0, let source = source, index < source.count else { return }
let vc = source[index]
let direction: UIPageViewControllerNavigationDirection = index < pageIndex ? .reverse : .forward
setViewController(vc, direction: direction, completion: completion)
}
private func setViewController(_ viewController: UIViewController, direction: UIPageViewControllerNavigationDirection = .forward, completion: ((Bool) -> Void)? = nil) {
super.setViewControllers([viewController], direction: direction, animated: false, completion: completion)
}
}
extension FFPageViewController: UIPageViewControllerDataSource {
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
guard let source = source, let index = source.index(of: viewController) else { return nil }
let count = source.count
if count == 2, index == 0 {
return nil
}
let prevIndex = (index - 1) < 0 ? count - 1 : index - 1
let pageContentViewController: UIViewController = source[prevIndex]
return pageContentViewController
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
guard let source = source, let index = source.index(of: viewController) else { return nil }
let count = source.count
if count == 2, index == 1 {
return nil
}
let nextIndex = (index + 1) >= count ? 0 : index + 1
let pageContentViewController = source[nextIndex]
return pageContentViewController
}
func presentationCount(for pageViewController: UIPageViewController) -> Int {
return showPageControl ? (source?.count ?? 0) : 0
}
func presentationIndex(for pageViewController: UIPageViewController) -> Int {
guard showPageControl else { return 0 }
return pageIndex
}
}
The overall implementation and usage examples one can find at GitHub project.
When UIPageViewController transition, ViewController inside it(ex: UITableViewController) transition will cause crash.
In my case (crash):
step1
self.pageViewController.setViewControllers([self.tableViewController2], direction: .forward, animated: true, completion: nil)
step2
Scroll the tableView while UIPageViewController transition.
My Solution
(disable scroll both target view controller and current view controller)
self.tableViewController1.tableView.isScrollEnabled = false
self.tableViewController2.tableView.isScrollEnabled = false
self.pageViewController.setViewControllers([self.tableViewController2], direction: .forward, animated: true, completion: { _ in
self.tableViewController1.tableView.isScrollEnabled = true
self.tableViewController2.tableView.isScrollEnabled = true
})
Move your pageViewController.setViewControllers function call inside DispatchQueue.main.async block if you are doing it in code.
I don't know why it works but it worked for me. For reference.
This happened to me too when I had textfields in child controller and didn't dismiss keyboard on scroll to next controller. If this is case just add endEditing in action where you programmatically change your controller or if you are scrolling on scrollViewDidScroll delegate method of pageViewController
This happens when your UIPageViewControllerTransitionStyle is set to scroll instead of pageCurl.
Are you dynamically creating View Controllers and setting them on UIPageViewController? In that case, you must ensure that the second call to setViewControllers is called after the first one completes animation because of a bug in UIKit. A delayed dispatch is a quick and dirty fix, though it is not a good practice
More details here.
https://forums.developer.apple.com/thread/6554
For me, the issue was using self.pageViewController as a member of the current view controller instead of pageViewController as parameter obtained in the didFinishAnimating delegate method.
Related
I am trying to jump to a specific page on a button press, I have made a ViewController which contains a ContainerView of the PageViewController, so that I can have permanent buttons on top. From there i do:
#IBAction func jump(_ sender: Any) {
PageViewController().jump()
}
and here is the Jump function in the PageViewController
func jump() {
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
lastNumber = lastCoinNumber
if let jumpView = viewControllerAtIndex(lastNumber, storyboard: self.storyboard!) {
self.setViewControllers([jumpView], direction: .forward, animated: false, completion: nil)
}
}
For some reason, I always get an error at the ViewControllerAtIndex part of the jump function:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
. even if I manually choose an index it does the same.
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!) {
self.setViewControllers([firstViewController], direction: .forward, animated: false, completion: nil)
}
Above is how I set up the ViewControllers initialy in viewDidLoad(), and that works fine, if I am essentially doing the same thing, why doesn't it work? Here is how I index the pages and instantiate the viewcontrollers, they use the same single ViewController so a new instance of it is created for each page, otherwise I would have created an array of viewControllers.
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) { if !completed { return }
DispatchQueue.main.async() {
self.dataSource = nil
self.dataSource = self
self.pageControl.numberOfPages = (Manager.shared.coins.count)
}
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
self.pageControl.currentPage = Manager.shared.coins.index(of: viewController.dataObject)!
return Manager.shared.coins.index(of: viewController.dataObject)!
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) {
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == -1 {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
I hope this is enough information, thank you.
Edit:
Coin is a string array, I declare this:
var last = Manager.shared.coins.last
var lastNumber: Int = 0
and then the jump() takes care of the rest. So I am getting the last object, finding its index, and then doing setViewControllers with the index of the last number, which should correspond with viewControllerAtIndex, because that uses the same array to index and load the pages.
for some reason, when I try to do:
var lastCoinNumber:Int = Manager.shared.coins.index(of: last)
It forces me to use ! because:
"Value of optional type 'Array.Index?' (aka 'Optional') not unwrapped; did you mean to use '!' or '?'?"
I'm not sure what I'm doing wrong in that regard, here is how coins is declared:
var coins = [""]
Edit: Code in full, PageViewController:
import UIKit
var pageView = PageViewController()
class PageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
//page Control dots
var pageControl = UIPageControl()
var last = Manager.shared.coins.last!
var lastNumber: Int = 0
var viewControllerArray = [UIViewController()]
func configurePageControl() {
// The total number of pages that are available is based on ManagerCoins names array
pageControl = UIPageControl(frame: CGRect(x: 0,y:
UIScreen.main.bounds.maxY - 50,width: UIScreen.main.bounds.width,height:
50))
self.pageControl.numberOfPages = (Manager.shared.coins.count)
self.pageControl.currentPage = 0
self.pageControl.tintColor = UIColor.black
self.pageControl.pageIndicatorTintColor = UIColor.gray
self.pageControl.currentPageIndicatorTintColor = UIColor.white
self.view.addSubview(pageControl)
}
// MARK: Delegate functions
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
self.pageControl.currentPage = Manager.shared.coins.index(of: viewController.dataObject)!
return Manager.shared.coins.index(of: viewController.dataObject)!
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) {
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == -1 {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func jump() {
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
lastNumber = lastCoinNumber
if let jumpView = viewControllerAtIndex(lastCoinNumber, storyboard: self.storyboard!){
self.setViewControllers([jumpView], direction: .forward, animated: false, completion: nil)
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.delegate = self
configurePageControl()
self.dataSource = self
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!){
self.setViewControllers([firstViewController], direction: .forward, animated: false, completion: nil)
}
}
}
Edit:
After much research, This seems to be the correct way to jump a page, by calling setViewControllers, the first comment on this answer seems to have the same problem, it works fine for setting the view on viewDidLoad() but trying to programmatically navigate to a page based on the index falls to an error. https://stackoverflow.com/a/24335008/10058239
I think it's crashing because of for force unwrapping:
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
if coins is a collection you can use .last to get the last element for example:
let numbers = [10, 20, 30, 40, 50]
if let lastNumber = numbers.last {
print(lastNumber)
}
// Prints "50"
I am trying to use PageViewController to generate new ViewControllers with data based on an array of names held in UserDefaults. When the user adds a new name into the array, the PageView should generate a new page on each swipe until the index is >= than the array.count.
The problem is while there are 5 items in the Array, I am able to swipe infinitely, the index works correctly for the first two pages, but it stays at 1 on each next swipe, so it never becomes == or >= so that it will return Nil. The array seems to be correct, when printing it prints the 5 names, but for some reason it is not indexing correctly in the pageView, can anyone Identify what the issue may be?
I hope this is enough information, Manager is the class where i hold the array called coins which contains at the moment 5 names of cryptocurrencies, the idea is to be able to add a new page, appending the array, and so that the pageView will generate a new page retrieving the data from an API to load the specific data for that coin, Very similar to the way the IOS weather app works. Thank you for the help, here is the code of the pageViewController:
import UIKit
class PageViewController: UIPageViewController,
UIPageViewControllerDataSource, UIPageViewControllerDelegate {
//page Control dots
var pageControl = UIPageControl()
func configurePageControl() {
// The total number of pages that are available is based on how
many available colors we have.
pageControl = UIPageControl(frame: CGRect(x: 0,y: UIScreen.main.bounds.maxY - 50,width: UIScreen.main.bounds.width,height: 50))
self.pageControl.numberOfPages = (Manager.shared.coins.count)
self.pageControl.currentPage = 0
self.pageControl.tintColor = UIColor.black
self.pageControl.pageIndicatorTintColor = UIColor.gray
self.pageControl.currentPageIndicatorTintColor = UIColor.white
self.view.addSubview(pageControl)
}
// MARK: Delegate functions
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
let pageContentViewController = pageViewController.viewControllers![0]
self.pageControl.currentPage = (viewControllers?.index(of: pageContentViewController)!)!
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
print(Manager.shared.coins)
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
print(viewController.dataObject)
return Manager.shared.coins.index(of: viewController.dataObject) ?? NSNotFound
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) || (index == NSNotFound){
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == NSNotFound {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
//List of View Controllers.
override func viewDidLoad() {
super.viewDidLoad()
self.delegate = self
configurePageControl()
self.dataSource = self
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!){
self.setViewControllers([firstViewController], direction: .forward, animated: true, completion: nil)
}
}
}
Coins:
class Manager {
var coins = [""]
let defaults = UserDefaults.standard
static let shared = Manager()
init() {
self.coins = self.defaults.stringArray(forKey: "SavedStringArray") ?? [String]()
}
func addCoin(coin:String) {
self.coins.append(coin)
self.defaults.set(self.coins, forKey: "SavedStringArray")
print ("coins from addCoin:")
print (self.coins)
}
}
and I add coins to the array from elsewhere like so:
#IBAction func goButton(_ sender: Any) {
self.choosePerm()
Manager.shared.coins.append(chosenCoin)
Manager.shared.addCoin(coin: chosenCoin)
print(Manager.shared.coins)
print(chosenCoin)
}
Edit: Above I've edited the way i append the array, choosePerm() gets the name of the coin after searching has been done, and chosenCoin is the coin chosen after search, it definitely is 1 name, but I am still getting it to append double each time, can you see anything In there that might be causing that? i.e. it prints
["Ethereum", "Boolberry", "Boolberry", "Bitcoin", "Bitcoin"]
You are appending the coin twice:
Manager.shared.coins.append(chosenCoin) // <-- appending for the first time
Manager.shared.addCoin(coin: chosenCoin) // <-- appending for the second time
func addCoin(coin:String) {
self.coins.append(coin) // <-- this is the second appending
This kind of error can be fixed but not allowing appending from outside the Manager class:
private(set) var coins = [""]
I'm trying to present a PageViewController with 3 ContentViewControllers where the user can move from one page to the next but also automate the scroll to the next page with a timer.
1st Question: How do I get the Page View Controller to properly update the dots on the bottom of the page.
I've implemented three page PageViewController and have a timer based automation. The timer calls:
#objc func animation() {
if counter < 2 {counter += 1}
else {counter = 0}
self.pageViewController.setViewControllers([self.pageTutorialAtIndex(counter)], direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil)
}
This call to setViewControllers changes the view. However, it does not update the PageViewController dots on the bottom of the page. What needs to be done to fix that?
And obviously this class level counter does not get the currently shown ViewContoller, which leads me to my second question.
2nd Question: How do I properly implement getting the current index from the page shown? I've tried:
let current = self.pageTutorialAtIndex(0) as SplashContentViewController
var counter : Int = current.pageIndex!
thinking that this reads the current page but it seems to only read the page 0.
The class and viewDidLoad are :
class SplashViewController: UIViewController, UIPageViewControllerDataSource {
var pageImages:NSArray!
var pageTitles:[String]!
var pageTexts:[String]!
var pageViewController:UIPageViewController!
var waitTimer : Timer!
var counter : Int = 0
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
pageImages = NSArray(objects:"sp_image1","sp_image2","sp_image3")
pageTitles = [NSLocalizedString("sp_title1",comment: ""), NSLocalizedString("sp_title2", comment: ""), NSLocalizedString("sp_title3", comment: "")]
pageTexts = [NSLocalizedString("sp_detail1",comment: ""), NSLocalizedString("sp_detail2", comment: ""), NSLocalizedString("sp_detail3", comment: "")]
self.pageViewController = self.storyboard?.instantiateViewController(withIdentifier: "SplashPageViewController") as! UIPageViewController
self.pageViewController.dataSource = self
let initialContenViewController = self.pageTutorialAtIndex(0) as SplashContentViewController
self.pageViewController.setViewControllers([initialContenViewController], direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMove(toParentViewController: self)
}
With the implement delegate methods:
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController?
{
let viewController = viewController as! SplashContentViewController
var index = viewController.pageIndex as Int
if(index == 0 || index == NSNotFound){return nil}
index -= 1
return self.pageTutorialAtIndex(index)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController?
{
let viewController = viewController as! SplashContentViewController
var index = viewController.pageIndex as Int
if((index == NSNotFound)){return nil}
index += 1
if(index == pageImages.count){return nil}
return self.pageTutorialAtIndex(index)
}
func presentationCount(for pageViewController: UIPageViewController) -> Int
{
return pageImages.count
}
func presentationIndex(for pageViewController: UIPageViewController) -> Int
{
return 0
}
I seem to have found one possible answer:
1st Question: How do I get the Page View Controller to properly update the dots on the bottom of the page. Rather than return 0, returning the current counter provides the right.
func presentationIndex(for pageViewController: UIPageViewController) -> Int
{
return counter
}
2nd Question: How do I implement getting the current index? In my solution the counter variable identifies the current page. It doesn't properly get the index from the page shown but it works.
Implementation with the global counter variable is:
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController?
{
let viewController = viewController as! SplashContentViewController
let index = viewController.pageIndex as Int
if(index == NSNotFound){
return nil
}
if(index > 0){
counter = index - 1
return self.pageTutorialAtIndex(counter)
} else {
counter = 0
return nil
}
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController?
{
let viewController = viewController as! SplashContentViewController
let index = viewController.pageIndex as Int
if((index == NSNotFound)){
return nil
}
if (index < pageImages.count - 1) {
counter = index + 1
return self.pageTutorialAtIndex(counter)
} else {
counter = pageImages.count - 1
return nil
}
}
Hi you are already setting the index of the current page in:
viewControllerBefore and viewControllerAfter
Just create a global variable and store the index value just before returning the view controller in each of those functions, something like
self.currentIndex = index
and then return the view controller in question
return self.pageTutorialAtIndex(index)
I am trying to load appropriate images from an array into my UIPageViewController's Views.
I have 3 views which I cycle through in order to prevent crashes.
I keep track whether I am scrolling forward or backwards but sometimes when flipping forth and back really quick, I run into a bug that flips the direction and than I get the same view repeating for couple of scrolls.
Here is the function that updates the local variable index when scrolling completes
func pageViewController(pvc: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed {
let thisPage = pvc.viewControllers!.last as! PageContentViewController
let currentIndex = thisPage.pageIndex
let lastIndex = lastPage.pageIndex
if(currentIndex > urlIndex){
urlIndex += 1
}else if(currentIndex < urlIndex) {
urlIndex -= 1
}else{
}
}
}
And here is the rest of my UIPageViewController code:
override func viewDidLoad() {
super.viewDidLoad()
dataSource = self
delegate = self
}
private(set) lazy var orderedViewControllers: [PageContentViewController] = {
return [self.newPageContentViewController(),
self.newPageContentViewController(),
self.newPageContentViewController()
]
}()
private func newPageContentViewController() -> PageContentViewController {
return UIStoryboard(name: "Main", bundle: nil) .
instantiateViewControllerWithIdentifier("PageContentViewController") as! PageContentViewController
}
private func getNextViewController() -> PageContentViewController{
let scrollView = orderedViewControllers.removeAtIndex(0)
orderedViewControllers.append(scrollView)
return scrollView
}
private func getPreviousViewController() -> PageContentViewController{
let scrollView = orderedViewControllers.removeLast()
orderedViewControllers.insert(scrollView, atIndex: 0)
return scrollView
}
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
guard urlIndex > 0 else {
return nil
}
let previousUrlIndex = urlIndex - 1
return getViewControllerAtIndex(previousUrlIndex, next: false)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController?
{
let nextUrlIndex = urlIndex + 1
guard arrayRouteName.count > nextUrlIndex else{
return nil
}
return getViewControllerAtIndex(nextUrlIndex, next: true)
}
func getViewControllerAtIndex(index: NSInteger, next: Bool) -> PageContentViewController
{
// Create a new view controller and pass suitable data.
var pageContentViewController:PageContentViewController
if(next){
pageContentViewController = getNextViewController()
}else{
pageContentViewController = getPreviousViewController()
}
pageContentViewController.localImage = arrayLocalImage[index]
pageContentViewController.pageIndex = index
pageContentViewController.view.clipsToBounds = true
return pageContentViewController
}
I have managed to fix the problem. I have removed the pageViewControllerfunction from the UIPageControllerDelegate an simply chaged my pageViewController functions in my data source to get the index from viewController like so
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
let index = ((viewController as! UIPageContentViewController).pageIndex) - 1
guard index < 0 {
return nil
}
return getViewControllerAtIndex(index, pageContentViewController: getPreviousViewController() )
}
and it behaves like it should.
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
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.