使用UIPageViewController子类在“之后”滑动时出现黑屏

Question

我试图在人们面临同样问题的现有问题中寻找答案，但这些问题的解决方案是我已经解决的问题。这是我的代码：

AppDelegate.swift

import UIKit

@UIApplicationMain
final class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        let onboardingCoordinator = OnboardingViewCoordinator()
        let onboardingPageViewController = WarmPushPageViewController(coordinator: onboardingCoordinator)
        self.window = UIWindow(frame: UIScreen.main.bounds)
        guard let window = self.window else { return false }
        window.rootViewController = onboardingPageViewController
        window.makeKeyAndVisible()

        return true
    }
}

您的典型应用代表，尽量保持尽可能小。

Coordinator.swift

import UIKit

enum PageViewDirection {
    case before
    case after
}

typealias Index = Int

protocol PageViewCoordinator: class {
    var currentIndex: Index { get set }
    var viewControllers: [UIViewController] { get set }
    func present(direction: PageViewDirection) -> UIViewController?
}

OnboardingViewCoordinator.swift

import UIKit

final class OnboardingViewCoordinator: PageViewCoordinator {
    var currentIndex: Index
    var viewControllers: [UIViewController]

    init() {
        self.viewControllers = [
            OnboardingTaglineViewController(nibName: nil, bundle: nil),
            OnboardingSourcesViewController(nibName: nil, bundle: nil)
        ]
        self.currentIndex = 0
    }

    func present(direction: PageViewDirection) -> UIViewController? {
        switch direction {
        case .before:
            if self.currentIndex == 0 {
                return nil
            }
            self.currentIndex -= 1
            let beforeVC = self.viewControllers[self.currentIndex]
            return beforeVC
        case .after:
            if self.currentIndex == (self.viewControllers.count - 1) {
                return nil
            }
            self.currentIndex += 1
            let afterVC = self.viewControllers[self.currentIndex]
            return afterVC
        }
    }
}

WarmPushPageViewController.swift

import UIKit

class WarmPushPageViewController: UIPageViewController {
    var coordinator: PageViewCoordinator? = nil

    convenience init(coordinator: PageViewCoordinator) {
        self.init(transitionStyle: .scroll,
                  navigationOrientation: .horizontal,
                  options: nil)
        self.setViewControllers([coordinator.viewControllers[coordinator.currentIndex]],
                                direction: .forward,
                                animated: true,
                                completion: nil)
        self.coordinator = coordinator
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
        self.dataSource = self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

extension WarmPushPageViewController: UIPageViewControllerDataSource {
    func pageViewController(_ pageViewController: UIPageViewController,
                            viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let coordinator = self.coordinator else { return nil }
        guard let beforeVC = coordinator.present(direction: .before) else { return nil }
        return beforeVC
    }

    func pageViewController(_ pageViewController: UIPageViewController,
                            viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let coordinator = self.coordinator else { return nil }
        guard let afterVC = coordinator.present(direction: .after) else { return nil }
        return afterVC
    }
}

提前致谢！

最佳， Kiren：）