如何以编程方式使用容器视图

Question

我创建了一个ViewController，我想在我的ViewController中添加一个容器视图，在这里我将容器视图设置在我的ViewController中：

var containerView: UIView = {
    let view = UIView()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = .red
    return view
}()

func setUpViews() {
    view.addSubview(containerView)
    containerView.heightAnchor.constraint(equalToConstant: 300).isActive = true
    containerView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    containerView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    containerView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
}

在这里，将我的SecondViewController实例设置在containerView中：

override func viewDidLoad() {
    super.viewDidLoad()

    setUpViews()

    let secondViewController = SecondViewController()

    secondViewController.willMove(toParent: self)

    containerView.addSubview(secondViewController.view)
    self.addChild(secondViewController)
    secondViewController.didMove(toParent: self)

}

在我的SecondViewController中，我声明了标签和一个视图，然后将标签设置在视图的中央：

let label: UILabel = {
    let label = UILabel()
    label.text = "Hello!"
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(myView)
        myView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        myView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        myView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        myView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true

        view.addSubview(label)
        label.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

    }

这就是我在应用程序中看到的内容，但是我偏偏在灰色视图的中心看到一个标签。 它不像我方面那样工作，我也不明白为什么。

Answer 1

您需要在加载的视图上设置框架和/或约束：

override func viewDidLoad() {
    super.viewDidLoad()

    setUpViews()

    let secondViewController = SecondViewController()

    secondViewController.willMove(toParent: self)

    containerView.addSubview(secondViewController.view)

    // set the frame
    secondViewController.view.frame = containerView.bounds

    // enable auto-sizing (for example, if the device is rotated)
    secondViewController.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]

    self.addChild(secondViewController)
    secondViewController.didMove(toParent: self)

}