UIPageViewController未调用委托方法(Swift 5)

Question

我的项目中有一个非常简单的UIPageViewController设置。当我创建页面视图控制器并导航到它时，一切似乎都正常工作，并且它正确地加载了第一个页面。但是，当我尝试滑动或切换到ViewControllers数组中的其他页面时，我的页面控制器不会调用其委托方法来执行此操作。

以下是我如何从父视图实例化和导航到页面视图控制器：

let tutorialPageVC = TareTutorialPageViewController()
let nc = UINavigationController(rootViewController: tutorialPageVC)
nc.modalPresentationStyle = .fullScreen
nc.definesPresentationContext = true
nc.setNavigationBarHidden(true, animated: true)
self.present(nc, animated: true, completion: nil)

这是我的页面视图控制器类：

import UIKit
class TareTutorialPageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
var tutorialPages = [UIViewController]()
let pageControl = UIPageControl()
override init(transitionStyle style: UIPageViewController.TransitionStyle, navigationOrientation: UIPageViewController.NavigationOrientation, options: [UIPageViewController.OptionsKey : Any]? = nil) {
super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: [:])
self.dataSource = self
self.delegate = self
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func viewDidLoad() {
super.viewDidLoad()
let initialTutorialPage = 0
let tutorialPage1 = TutorialPage1ViewController()
let tutorialPage2 = TutorialPage2ViewController()
let tutorialPage3 = TutorialPage3ViewController()
self.tutorialPages.append(tutorialPage1)
self.tutorialPages.append(tutorialPage2)
self.tutorialPages.append(tutorialPage3)
setViewControllers([tutorialPages[initialTutorialPage]], direction: .forward, animated: true, completion: nil)
self.pageControl.frame = CGRect()
self.pageControl.currentPageIndicatorTintColor = UIColor.white
self.pageControl.pageIndicatorTintColor = UIColor.lightGray
self.pageControl.numberOfPages = self.tutorialPages.count
self.pageControl.currentPage = initialTutorialPage
self.view.addSubview(self.pageControl)
self.pageControl.translatesAutoresizingMaskIntoConstraints = false
self.pageControl.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -5).isActive = true
self.pageControl.widthAnchor.constraint(equalTo: self.view.widthAnchor, constant: -20).isActive = true
self.pageControl.heightAnchor.constraint(equalTo: self.view.heightAnchor, constant: 20).isActive = true
self.pageControl.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
//Might not need any of this if we only want the user to move forward??
if let viewControllerIndex = self.tutorialPages.firstIndex(of: viewController)
{
if viewControllerIndex == 0
{
return self.tutorialPages.last
}
else
{
return self.tutorialPages[viewControllerIndex-1]
}
}
return nil
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
if let viewControllerIndex = self.tutorialPages.firstIndex(of: viewController)
{
if viewControllerIndex < self.tutorialPages.count - 1
{
return self.tutorialPages[viewControllerIndex + 1]
}
else
{
//Navigation to go to scale tare settings here...
//For now just returns to first page of page view
return self.tutorialPages.first
}
}
return nil
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if let viewControllers = pageViewController.viewControllers {
if let viewControllerIndex = self.tutorialPages.firstIndex(of: viewControllers[0])
{
self.pageControl.currentPage = viewControllerIndex
}
}
}

}

下面是我的一个非常简单的视图控制器的例子，它由页面视图控制器显示：

import UIKit
class TutorialPage1ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.black
let label = UILabel()
label.text = "Tutorial page 1"
label.textColor = UIColor.white
self.view.addSubview(label)
label.translatesAutoresizingMaskIntoConstraints = false
label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50).isActive = true
label.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: 20).isActive = true
}
}

Answer 1

问题不在于没有调用委托函数，问题在于您将UIPageViewController与UIPageControl完全重叠。

您可以通过添加以下行来确认：

// existing line
self.view.addSubview(self.pageControl)
// add this line
self.pageControl.backgroundColor = .orange

像这样更改您的约束设置：

// completely remove these lines
//self.pageControl.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -5).isActive = true
//self.pageControl.widthAnchor.constraint(equalTo: self.view.widthAnchor, constant: -20).isActive = true
//self.pageControl.heightAnchor.constraint(equalTo: self.view.heightAnchor, constant: 20).isActive = true
//self.pageControl.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
pageControl.widthAnchor.constraint(equalTo: g.widthAnchor, constant: -20.0),
pageControl.centerXAnchor.constraint(equalTo: g.centerXAnchor),
pageControl.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -5.0),
])

现在，您应该可以看到底部的页面控件，并且可以在页面中滑动。

顺便说一句，UIPageViewController有一个"内置"的UIPageControl，无论如何你可能会发现它效果更好。