UIPageViewController实现滑动切换控制器边缘露底问题及方案咨询

1. 修复UIPageViewController边界滑动透出背景问题 #

你遇到的边界滑动透出背景是UIPageViewController内部UIScrollView默认开启的回弹效果导致的，只需要关闭该回弹属性即可。
在presentPageVC方法中初始化UIPageViewController后，添加以下代码找到内部ScrollView并关闭回弹：

// 遍历UIPageViewController的子视图找到UIScrollView
for subview in vc.view.subviews {
    if let scrollView = subview as? UIScrollView {
        scrollView.bounces = false
    }
}

你当前的UIPageViewController数据源实现是正确的，边界处返回nil就不会加载额外页面，关闭回弹后就不会出现滑动透出背景的问题。

2. 更适合新手的实现方案（UIScrollView方案） #

对于新手来说，UIScrollView实现的逻辑更直观可控，不存在UIPageViewController的隐藏适配问题，你之前疑惑的VC视图添加问题可以通过苹果官方的「子视图控制器」机制解决，不需要把VC转成View，只需要做好层级关联即可：

完整实现示例代码 #

class ViewController: UIViewController {
    // 声明需要切换的两个视图控制器
    let chatVC = one()
    let cameraVC = two()
    // 滚动容器
    let scrollView: UIScrollView = {
        let scroll = UIScrollView()
        scroll.isPagingEnabled = true // 开启分页效果
        scroll.bounces = false // 关闭边界回弹
        scroll.showsHorizontalScrollIndicator = false
        return scroll
    }()
    // 内容容器
    let contentView: UIView = {
        let view = UIView()
        return view
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        setupLayout()
        setupChildViewControllers()
    }
    
    private func setupLayout() {
        // 添加scrollView到当前视图
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(scrollView)
        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
        
        // 添加contentView到scrollView
        contentView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(contentView)
        let screenWidth = view.bounds.width
        NSLayoutConstraint.activate([
            contentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
            contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
            contentView.heightAnchor.constraint(equalTo: scrollView.heightAnchor),
            contentView.widthAnchor.constraint(equalToConstant: screenWidth * 2) // 两个页面，宽度是2倍屏宽
        ])
    }
    
    private func setupChildViewControllers() {
        let screenWidth = view.bounds.width
        // 添加chatVC为子视图控制器
        addChild(chatVC)
        chatVC.view.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(chatVC.view)
        chatVC.didMove(toParent: self)
        
        // 添加cameraVC为子视图控制器
        addChild(cameraVC)
        cameraVC.view.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(cameraVC.view)
        cameraVC.didMove(toParent: self)
        
        // 布局两个子VC的视图
        NSLayoutConstraint.activate([
            chatVC.view.topAnchor.constraint(equalTo: contentView.topAnchor),
            chatVC.view.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            chatVC.view.widthAnchor.constraint(equalToConstant: screenWidth),
            chatVC.view.heightAnchor.constraint(equalTo: contentView.heightAnchor),
            
            cameraVC.view.topAnchor.constraint(equalTo: contentView.topAnchor),
            cameraVC.view.leadingAnchor.constraint(equalTo: chatVC.view.trailingAnchor),
            cameraVC.view.widthAnchor.constraint(equalToConstant: screenWidth),
            cameraVC.view.heightAnchor.constraint(equalTo: contentView.heightAnchor)
        ])
    }
}

方案优势 #

• 逻辑完全透明，没有UIPageViewController的隐式行为，出问题容易排查
• 后续扩展到5个页面仅需要添加对应的子VC，修改contentView的宽度约束即可
• 不需要处理复杂的数据源和代理方法，新手更容易理解

3. 常见疑问解答 #

• UICollectionView实现不需要把UIViewController转成Cell：只需将子VC的view添加到Cell的contentView上，同时做好子VC的父级关联即可，不过该方案需要处理Cell复用逻辑，对于新手来说门槛更高，熟悉视图层级后再尝试即可
• UIScrollView添加VC子视图的核心就是子视图控制器机制：调用addChild(_:)方法把子VC加入当前父VC，再把子VC的view添加到ScrollView对应位置，最后调用子VC的didMove(toParent:)方法，系统就会自动管理子VC的生命周期，viewWillAppear、viewWillDisappear等系统方法都会正常触发

内容的提问来源于stack exchange，提问作者Mr N