问题

Question

问题

点击页面i上的跳过按钮（调用setViewControllers(_:animated:)并将用户转移到页面视图控制器中的最后一页），然后再次滑回页面i ，页面控件消失。

通缉结果

当所述页面视图控制器包含不同类型的视图控制器时，我希望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。

目前为解决问题所做的努力

每次出现时都将页面控件添加到基本视图控制器。
在包含缺少页面控件的视图控制器上调用loadView()。

代码

我的WalkthroughRootViewController包含UIPageViewController。页面视图控制器中视图控制器的类型是类型WalkthroughBaseViewController的两个子类，一种类型的第一个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。

我在WalkthroughBaseViewController中有这段代码：

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
}()

页面控件已添加到viewDidLoad()：

中的视图中

view.addSubview(pageControl)
NSLayoutConstraint.activate([
    pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor),
    pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor)
])

如果用户位于任何第一个n-1视图控制器上，则会有一个跳过按钮，用户可以点按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)
}

参考

我突出显示了我认为重要的代码，但以下是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 {
}

Answer 1

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。

尽量不要使用extension来覆盖方法 - 这可能会给您带来麻烦 - 请参阅this blog entry。

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

问题