Programmatically-added page control disappears when setting view controllers after setup - ios

Question

Problem
When tapping the skip button on page i (which calls setViewControllers(_:animated:) and transitions the user to the last page in the page view controller), and then swiping back to page i again, the page control disappears.
Wanted result
I want to programmatically add and show a custom page control on the bottom of each view controller in a page view controller when said page view controller contains different types of view controllers.
Efforts so far to resolve the issue
Adding the page control to the base view controller each time it appears.
Calling loadView() on the view controller that contains the missing page control.
Code
I have a WalkthroughRootViewController that contains a UIPageViewController. The type of the view controllers in the page view controller are two subclasses of type WalkthroughBaseViewController, the first n-1 of one type, and the last of the other. I have not included code of the last type, as that's working as far as I can see.
I have this code in WalkthroughBaseViewController:
lazy var pageControl: UIPageControl = {
let pageControl = UIPageControl(frame: .zero)
pageControl.translatesAutoresizingMaskIntoConstraints = false
pageControl.numberOfPages = numberOfPages
pageControl.sizeToFit()
pageControl.pageIndicatorTintColor = Colors.brown
pageControl.currentPageIndicatorTintColor = Colors.silver
pageControl.isUserInteractionEnabled = false
pageControl.isEnabled = false
return pageControl
}()
The page control is added to the view in viewDidLoad():
view.addSubview(pageControl)
NSLayoutConstraint.activate([
pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor),
pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor)
])
If the user is on any of the first n-1 view controllers, there is a skip button the user can tap to skip forward to the last view controller. The code for this is
func skipWalkthrough() {
guard let viewController = walkthroughPageViewControllerDataSource.viewController(at: lastIndex, storyboard: storyboard!) else { return }
walkthroughPageViewController.setViewControllers([viewController], direction: .forward, animated: true)
}
Reference
I have highlighted the code I believe is important, but here are all files related to the walkthrough of the application.
WalkthroughRootViewController
import UIKit
class WalkthroughRootViewController: UIViewController {
// MARK: Regular Properties
var walkthroughPageViewController: UIPageViewController!
var walkthroughImages = [
Images.w1,
Images.w2
]
var walkthroughStrings: [String] = [
.localized(.walkthroughTitle1),
.localized(.walkthroughZipCodeTitle)
]
// MARK: Lazy Properties
lazy var walkthroughPageViewControllerDataSource: WalkthroughPageViewControllerDataSource = {
var dataSource = WalkthroughPageViewControllerDataSource()
dataSource.walkthroughRootViewController = self
return dataSource
}()
// MARK: Computed Properties
var lastIndex: Int {
return walkthroughImages.count - 1
}
var temporaryUserInput: String?
var temporarySwitchPosition = false
override var preferredStatusBarStyle: UIStatusBarStyle {
return .lightContent
}
}
// MARK: View Controller Life Cycle
extension WalkthroughRootViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Stop gray shadow from appearing under transition.
navigationController?.view.backgroundColor = .white
configurePageViewController()
}
}
// MARK: Helper Methods
extension WalkthroughRootViewController {
func configurePageViewController() {
walkthroughPageViewController = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
walkthroughPageViewController.dataSource = walkthroughPageViewControllerDataSource
walkthroughPageViewController.delegate = walkthroughPageViewControllerDataSource
let startingViewController = storyboard!.instantiateViewController(withIdentifier: Strings.ViewControllerIdentifiers.walkthroughImage) as! WalkthroughImageViewController
let startIndex = 0
startingViewController.delegate = self
startingViewController.pageIndex = startIndex
startingViewController.text = walkthroughStrings[startIndex]
startingViewController.image = walkthroughImages[startIndex]
startingViewController.numberOfPages = walkthroughImages.count
walkthroughPageViewController.setViewControllers([startingViewController], direction: .forward, animated: true)
walkthroughPageViewController.view.frame = view.bounds
add(walkthroughPageViewController)
}
}
extension WalkthroughRootViewController: WalkthroughDelegate {
func skipWalkthrough() {
guard let viewController = walkthroughPageViewControllerDataSource.viewController(at: lastIndex, storyboard: storyboard!) else { return }
walkthroughPageViewController.setViewControllers([viewController], direction: .forward, animated: true)
}
}
extension WalkthroughRootViewController: WalkthrouZipCodeViewControllerDelegate {
func walkththroughZipCodeViewController(_ viewController: WalkthroughZipCodeViewController, userEnteredText enteredText: String) {
temporaryUserInput = enteredText
}
func walkthroughZipCodeViewController(_ viewController: WalkthroughZipCodeViewController, userChangedSwitchPosition position: Bool) {
temporarySwitchPosition = position
}
}
WalkthroughBaseViewController
import UIKit
protocol WalkthroughDelegate: class {
func skipWalkthrough()
}
class WalkthroughBaseViewController: UIViewController {
// MARK: Regular Properties
var pageIndex = 0
var text = ""
var delegate: WalkthroughDelegate?
var numberOfPages = 0
// Lazy Properties
lazy var pageControl: UIPageControl = {
let pageControl = UIPageControl(frame: .zero)
pageControl.translatesAutoresizingMaskIntoConstraints = false
pageControl.numberOfPages = numberOfPages
pageControl.sizeToFit()
pageControl.pageIndicatorTintColor = Colors.brown
pageControl.currentPageIndicatorTintColor = Colors.silver
pageControl.isUserInteractionEnabled = false
pageControl.isEnabled = false
return pageControl
}()
}
// MARK: View Controller Life Cycle
extension WalkthroughBaseViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = Colors.silver
view.addSubview(pageControl)
NSLayoutConstraint.activate([
pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor),
pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor)
])
view.accessibilityIdentifier = Strings.AccessibilityIdentifiers.walkthrough
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
pageControl.currentPage = pageIndex
}
}
WalkthroughImageViewController
import UIKit
class WalkthroughImageViewController: WalkthroughBaseViewController {
// MARK: #IBOutlets
#IBOutlet weak var titleLabel: UILabel! {
didSet {
titleLabel.adjustsFontSizeToFitWidth = true
titleLabel.textColor = Colors.silver
titleLabel.numberOfLines = 0
}
}
#IBOutlet weak var skipWalkthroughButton: UIButton! {
didSet {
skipWalkthroughButton.setTitleColor(Colors.silver, for: .normal)
skipWalkthroughButton.titleLabel?.font = UIFont.preferredBoldFont(for: .body)
skipWalkthroughButton.setTitle(.localized(.skip), for: .normal)
}
}
#IBOutlet weak var imageView: UIImageView! {
didSet {
imageView.layer.shadowColor = Colors.brown.cgColor
imageView.layer.shadowOffset = CGSize(width: 0, height: 1)
imageView.layer.shadowOpacity = 1
imageView.layer.shadowRadius = 1.0
imageView.clipsToBounds = false
imageView.contentMode = .scaleAspectFill
}
}
// MARK: Regular Properties
var image: UIImage?
// MARK: View Controller Life Cycle
override func viewDidLoad() {
super.viewDidLoad()
imageView.image = image
titleLabel.text = text
}
}
// MARK: #IBActions
extension WalkthroughImageViewController {
#IBAction func skipWalkthrough(_ sender: UIButton) {
delegate?.skipWalkthrough()
}
}
WalkthroughPageViewControllerDataSource
import UIKit
class WalkthroughPageViewControllerDataSource: NSObject {
// MARK: Regular Properties
var walkthroughRootViewController: WalkthroughRootViewController!
}
extension WalkthroughPageViewControllerDataSource: UIPageViewControllerDataSource {
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = indexOfViewController(viewController as! WalkthroughBaseViewController)
if index == NSNotFound || index == 0 {
return nil
}
index -= 1
return self.viewController(at: index, storyboard: walkthroughRootViewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = indexOfViewController(viewController as! WalkthroughBaseViewController)
if index == NSNotFound {
return nil
}
index += 1
if index == walkthroughRootViewController.walkthroughImages.count {
return nil
}
return self.viewController(at: index, storyboard: walkthroughRootViewController.storyboard!)
}
}
extension WalkthroughPageViewControllerDataSource {
func viewController(at index: Int, storyboard: UIStoryboard) -> WalkthroughBaseViewController? {
if walkthroughRootViewController.walkthroughImages.count == 0 || index >= walkthroughRootViewController.walkthroughImages.count {
return nil
}
var viewController: WalkthroughBaseViewController?
if index == walkthroughRootViewController.lastIndex {
viewController = storyboard.instantiateViewController(withIdentifier: Strings.ViewControllerIdentifiers.walkthroughZipCode) as? WalkthroughZipCodeViewController
if let viewController = viewController as? WalkthroughZipCodeViewController {
viewController.pageIndex = index
viewController.walkthroughZipCodeDelegate = walkthroughRootViewController
viewController.temporaryUserInput = walkthroughRootViewController.temporaryUserInput
viewController.temporarySwitchPosition = walkthroughRootViewController.temporarySwitchPosition
viewController.numberOfPages = walkthroughRootViewController.walkthroughImages.count
viewController.image = walkthroughRootViewController.walkthroughImages[index]
}
} else {
viewController = storyboard.instantiateViewController(withIdentifier: Strings.ViewControllerIdentifiers.walkthroughImage) as? WalkthroughImageViewController
if let viewController = viewController as? WalkthroughImageViewController {
viewController.delegate = walkthroughRootViewController
viewController.pageIndex = index
viewController.image = walkthroughRootViewController.walkthroughImages[index]
viewController.text = walkthroughRootViewController.walkthroughStrings[index]
}
}
return viewController
}
func indexOfViewController(_ viewController: WalkthroughBaseViewController) -> Int {
return viewController.pageIndex
}
}
extension WalkthroughPageViewControllerDataSource: UIPageViewControllerDelegate {
}

Answer 1

Create a single UIPageControl that you put in the WalkthroughRootViewController and update it when you navigate the pages - don't create a page control for each child.
Try not to use extensions to override methods - it can cause you trouble - see this blog entry.