Swift UIPageViewController - 用于请求的脊椎位置 (UIPageViewControllerSpineLocationMin)答案

【问题标题】：Swift UIPageViewController - for the requested spine location (UIPageViewControllerSpineLocationMin)Swift UIPageViewController - 用于请求的脊椎位置 (UIPageViewControllerSpineLocationMin)
【发布时间】：2021-01-18 22:06:37
【问题描述】：

我在这里以编程方式创建了 UIPageViewController。 当我将多个 ViewController 加载到 UIPageViewController 时。应用崩溃了。

在下面检查我的代码。

class PageVC: UIPageViewController {
    
    let colors = [UIColor.green, UIColor.red, UIColor.blue, UIColor.black]

    var pages: [UIViewController] = []
    
    override var spineLocation: UIPageViewController.SpineLocation {
        return .min
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.isDoubleSided = true
        
        colors.forEach({
            let page = UIViewController()
            page.view.backgroundColor = $0
            pages.append(page)
        })
        
        self.view.backgroundColor = UIColor.red
        
        self.setViewControllers(pages, direction: UIPageViewController.NavigationDirection.forward, animated: true, completion: nil)
    }
}

出现如下错误。

帮我解决这个问题。

【问题讨论】：

尝试设置pageViewController.isDoubleSided = true

标签： ios uikit uipageviewcontroller swift5 xcode12

【解决方案1】：

我从另一个角度面临同样的问题。在初始化UIPageViewController 时，我试图从options 更改脊椎位置。按照 Apple 文档，我尝试将首选脊椎位置包装到 NSNumber 并将其设置为选项字典中 spineLocation 键的值，但应用程序总是崩溃。不知道为什么...

实际上，我知道以编程方式更改脊椎位置的唯一方法是在委托方法spineLocationFor orientation 中返回选定的脊椎位置。您必须创建另一个 ViewController 并将自定义 PageViewController 添加为子项。我知道这不是您问题的确切答案，但希望对您有所帮助。通过代码，使用 UIPageViewController：

class ViewController: UIViewController {

private var pageController: UIPageViewController?

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

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    pageController?.view.frame = CGRect(x: 0,
                                        y: 0,
                                        width: self.view.frame.width,
                                        height: self.view.frame.height)
}

private func setupPageController() {
    self.pageController = UIPageViewController(transitionStyle: .pageCurl, navigationOrientation: .horizontal, options: nil)
    self.pageController?.dataSource = self
    self.pageController?.delegate = self
    self.addChild(self.pageController!)
    self.view.addSubview(self.pageController!.view)

    self.pageController?.setViewControllers([UIViewController()], direction: .forward, animated: true, completion: nil)
            
    self.pageController?.didMove(toParent: self)
}
}

extension ViewController: UIPageViewControllerDataSource, UIPageViewControllerDelegate {

func pageViewController(_ pageViewController: UIPageViewController, spineLocationFor orientation: UIInterfaceOrientation) -> UIPageViewController.SpineLocation {

    // handle orientation cases if needed
    // assuming you only support landscape:

    let initialVC = UIViewController()
    let initialVC2 = UIViewController()
    self.pageController?.setViewControllers([initialVC, initialVC2], direction: .forward, animated: true, completion: nil)
    pageController?.isDoubleSided = true
    return .mid
    }
}

【讨论】：