在设置后设置视图控制器时，以编程方式添加的页面控件消失

时间：2020-12-27 22:40:34

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.

当点击页面i上的跳过按钮（调用setViewControllers（_：animated :)并将用户转换到页面视图控制器中的最后一页），然后再次向后滑动到页面i时，页面控件将消失。

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.

当所述页面视图控制器包含不同类型的视图控制器时，我想以编程方式在页面视图控制器中的每个视图控制器的底部添加和显示自定义页面控件。

Efforts so far to resolve the issue

  • Adding the page control to the base view controller each time it appears.
  • 每次出现时都将页面控件添加到基本视图控制器。
  • Calling loadView() on the view controller that contains the missing page control.
  • 在包含缺少页面控件的视图控制器上调用loadView（）。

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.

我有一个包含UIPageViewController的WalkthroughRootViewController。页面视图控制器中视图控制器的类型是WalkthroughBaseViewController类型的两个子类，一个类型的第一个n-1，另一个类型的最后一个。我没有包含最后一种类型的代码，因为我可以看到它的工作。

I have this code in WalkthroughBaseViewController:

我在WalkthroughBaseViewController中有这个代码：

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():

页面控件添加到viewDidLoad（）中的视图：

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

如果用户在第一个n-1视图控制器中的任何一个上，则有一个跳过按钮，用户可以点击该按钮以跳到最后一个视图控制器。这个代码是

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.

我已经突出显示了我认为很重要的代码，但这里有与应用程序演练相关的所有文件。

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 {
}

1 个解决方案

#1

2  

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.

创建一个放在WalkthroughRootViewController中的UIPageControl，并在导航页面时更新它 - 不要为每个子项创建页面控件。

Try not to use extensions to override methods - it can cause you trouble - see this blog entry.

尽量不要使用扩展来覆盖方法 - 它可能会给您带来麻烦 - 请参阅此博客条目。

#1

2  

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.

创建一个放在WalkthroughRootViewController中的UIPageControl，并在导航页面时更新它 - 不要为每个子项创建页面控件。

Try not to use extensions to override methods - it can cause you trouble - see this blog entry.

尽量不要使用扩展来覆盖方法 - 它可能会给您带来麻烦 - 请参阅此博客条目。

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