Swift 4：通过按钮切换Page View Controller无效果，求解决方案

可能的问题排查方向 #

• 容器视图与PageVC的关联问题：如果你的CustomPageViewController没有被正确添加到MainViewController的容器视图中，或者约束没设置到位，哪怕调用了切换方法，页面也不会有变化。一定要确保PageVC的view被添加到容器视图，并且设置了全屏约束。
• 按钮IBAction未正确绑定：检查Storyboard或XIB里的按钮是不是真的连到了你写的切换方法上，有时候连线会不小心断开，或者方法名拼写错误导致触发不了。
• PageVC数据源/代理未实现：CustomPageViewController必须实现UIPageViewControllerDataSource的核心方法，否则PageVC不知道切换时该展示哪个视图控制器，自然没反应。
• 切换方法调用错误：不要直接修改PageVC的viewControllers属性，必须用官方提供的setViewControllers:direction:animated:completion:方法来触发页面切换，这才是PageVC认可的切换方式。

可正常运行的MainViewController代码 #

import UIKit

class MainViewController: UIViewController {
    // 容器视图，需在Storyboard中添加并关联IBOutlet
    @IBOutlet weak var pageContainerView: UIView!
    // 自定义PageVC实例
    private var customPageVC: CustomPageViewController!
    // 记录当前页面索引
    private var currentPageIndex = 0
    // 预定义的子视图控制器数组
    private let childViewControllers: [UIViewController] = {
        let vc1 = UIViewController()
        vc1.view.backgroundColor = .systemRed
        vc1.title = "页面1"
        
        let vc2 = UIViewController()
        vc2.view.backgroundColor = .systemBlue
        vc2.title = "页面2"
        
        let vc3 = UIViewController()
        vc3.view.backgroundColor = .systemGreen
        vc3.title = "页面3"
        
        return [vc1, vc2, vc3]
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupCustomPageVC()
    }

    // 初始化并挂载CustomPageVC到容器视图
    private func setupCustomPageVC() {
        customPageVC = CustomPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal)
        customPageVC.dataSource = self
        
        // 设置初始显示的页面
        customPageVC.setViewControllers([childViewControllers[currentPageIndex]], direction: .forward, animated: false, completion: nil)
        
        // 将PageVC添加为子控制器并嵌入容器
        addChild(customPageVC)
        customPageVC.view.frame = pageContainerView.bounds
        pageContainerView.addSubview(customPageVC.view)
        customPageVC.didMove(toParent: self)
        
        // 配置AutoLayout约束（替代frame布局）
        customPageVC.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            customPageVC.view.topAnchor.constraint(equalTo: pageContainerView.topAnchor),
            customPageVC.view.leadingAnchor.constraint(equalTo: pageContainerView.leadingAnchor),
            customPageVC.view.trailingAnchor.constraint(equalTo: pageContainerView.trailingAnchor),
            customPageVC.view.bottomAnchor.constraint(equalTo: pageContainerView.bottomAnchor)
        ])
    }

    // 上一页按钮触发方法
    @IBAction func previousPageTapped(_ sender: UIButton) {
        guard currentPageIndex > 0 else { return }
        currentPageIndex -= 1
        customPageVC.setViewControllers([childViewControllers[currentPageIndex]], direction: .reverse, animated: true, completion: nil)
    }

    // 下一页按钮触发方法
    @IBAction func nextPageTapped(_ sender: UIButton) {
        guard currentPageIndex < childViewControllers.count - 1 else { return }
        currentPageIndex += 1
        customPageVC.setViewControllers([childViewControllers[currentPageIndex]], direction: .forward, animated: true, completion: nil)
    }
}

// 实现UIPageViewControllerDataSource协议，支持滑动切换
extension MainViewController: UIPageViewControllerDataSource {
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let index = childViewControllers.firstIndex(of: viewController), index > 0 else { return nil }
        return childViewControllers[index - 1]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let index = childViewControllers.firstIndex(of: viewController), index < childViewControllers.count - 1 else { return nil }
        return childViewControllers[index + 1]
    }
}

// 自定义PageViewController类
class CustomPageViewController: UIPageViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 可添加自定义配置，比如隐藏页面指示器
        self.navigationItem.hidesBackButton = true
    }
}

额外提示 #

• 如果你使用Objective-C，核心逻辑完全一致，只是语法不同：正确添加子控制器、绑定按钮事件、实现数据源协议、调用setViewControllers:方法切换。
• 务必确认Storyboard中的容器视图、按钮已正确关联到代码中的IBOutlet和IBAction，可通过右键点击控件查看连线状态。

内容的提问来源于stack exchange，提问作者R1'