如何以编程方式在 UIPageViewController 中放置自动布局约束？

Question

I am trying to get to display content in a UIPageViewController, but I had no luck so far. I was able to display the page view dots, and the background colour (teal) applies correctly, but that's about it.

In my code, I have a PageViewController inheriting from UIPageViewController, and InPageViewController inheriting from UIViewController as the content pages inside the parent view.

Inside InPageViewController:

    private let labelView: UILabel = {
        let label = UILabel()
//        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = "Label"

        return label
    }()

    init(data: PageData) {
        super.init(nibName: nil, bundle: nil)
        labelView.text = data.dataName
        view.backgroundColor = .systemTeal
        view.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(labelView)

//        These are the constraints I am trying to set. Tried lots of different variations already 
//        NSLayoutConstraint.activate([
//            labelView.centerXAnchor.constraint(equalTo: view.layoutMarginsGuide.centerXAnchor),
//            labelView.centerYAnchor.constraint(equalTo: view.layoutMarginsGuide.centerYAnchor),
//        ])
    }

This is the current state that I get to display the background colour, but not the label. Whenever I add the constraints array, the background disappears, and reverts to its default grey colour, which I have set in PageViewController .

    let dataArray = [PageData(dataName: "Data"), PageData(dataName: "Lore")]

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

    func setupView() {
        title = "A fistful of Datas"
    }

    lazy var arrayInPageViewController: [InPageViewController] = {
        var inPageVC = [InPageViewController]()
        for data in dataArray {
            inPageVC.append(InPageViewController(data: data))
        }
        return inPageVC
    }()

    override init(transitionStyle style: UIPageViewController.TransitionStyle, navigationOrientation: UIPageViewController.NavigationOrientation, options: [UIPageViewController.OptionsKey : Any]? = nil) {
        super.init(transitionStyle: .scroll, navigationOrientation: navigationOrientation, options: nil)

        self.dataSource = self
        self.delegate = self

        self.view.backgroundColor = .systemGray
        setViewControllers([arrayInPageViewController[0]], direction: .forward, animated: true, completion: nil)
        print(dataArray)
    }

Here I am setting the parent view. I also have an extension, in which I run the stubs.

I am relatively new to programming in general, and I am still having trouble understanding the auto-layout logic in Swift, so any help is appreciated.

Answer 1

You need to set labelView.translatesAutoresizingMaskIntoConstraints to false instead of view.translatesAutoresizingMaskIntoConstraints