我正在进行一个练习项目，试图实现这一目标。
使用UIView Subclassing我几乎完成了它，我与一些 SF 开发人员一起编写了这段代码。
class Luna: UIView {
private var screenWidth: CGFloat {
return UIScreen.main.bounds.width
}
override init(frame: CGRect) {
super.init(frame: frame)
}
required public init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
public func showLuna(inView: UIView, title messageTitle:String, message messageDescription:String, dissmiss dissmissDuration: TimeInterval) {
let luna = UIView()
let titleLabel = UILabel()
titleLabel.text = "Introducing our new football notifications on the Guardian app"
titleLabel.font = UIFont(name: "avenirnext-demibold", size: 13)
//titleLabel.textColor = UIColor(hexString: "4A4A4A")
titleLabel.numberOfLines = 0 // whole idea of self-sizing
let titleDesc = UILabel()
titleDesc.text = "Today we are excited to announce the launch of our new and improved football notifications in our latest update to the Guardian app."
titleDesc.font = UIFont(name: "avenirnext-regular", size: 9)
//titleDesc.textColor = UIColor(hexString: "4A4A4A")
titleDesc.numberOfLines = 0
// My mainView
luna.backgroundColor = .white
//luna.addShadow(radius: 11, opacity: 0.2) // Some Shadow
luna.layer.cornerRadius = 10
let verticalStackView = UIStackView(arrangedSubviews: [titleLabel, titleDesc])
verticalStackView.axis = .vertical
let okButton = UIButton()
okButton.setTitleColor(.blue, for: .normal)
// okButton.setTitle("Okay", for: .normal)
okButton.setContentHuggingPriority(.defaultHigh, for: .horizontal) // to stretch the okay button horizontally
let horizontalStackView = UIStackView(arrangedSubviews: [verticalStackView, okButton])
horizontalStackView.axis = .horizontal
luna.addSubview(horizontalStackView)
self.addSubview(luna)
horizontalStackView.translatesAutoresizingMaskIntoConstraints = false // when using autolayout from code, this property must be false, otherwise constraint won't work
luna.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
horizontalStackView.topAnchor.constraint(equalTo: luna.topAnchor, constant: 8),
horizontalStackView.bottomAnchor.constraint(equalTo: luna.bottomAnchor, constant: -8),
horizontalStackView.leadingAnchor.constraint(equalTo: luna.leadingAnchor, constant: 8),
horizontalStackView.trailingAnchor.constraint(equalTo: luna.trailingAnchor, constant: -8),
luna.topAnchor.constraint(equalTo: inView.safeAreaLayoutGuide.topAnchor, constant: 30),
luna.leadingAnchor.constraint(equalTo: inView.safeAreaLayoutGuide.leadingAnchor, constant: 30),
luna.trailingAnchor.constraint(equalTo: inView.safeAreaLayoutGuide.trailingAnchor, constant: -30)
])
}
}
但是，在调用Show Luna我的另一个 ViewController 时，该应用程序崩溃并给出以下信息：
2018-07-11 10:45:08.999314+0300 LunaView[1344:23604] *** 由于未捕获的异常“NSGenericException”而终止应用程序，原因：“无法使用锚点激活约束，因为它们没有共同的祖先。约束或其锚点是否引用不同视图层次结构中的项目？这是非法的。
考虑到要提供的无效视图，我猜测应用程序会因为限制而崩溃。Show Luna将代码粘贴到ViewDidLoad另一个视图控制器中是可行的，那就是如果您将InView约束更改为self.view：
但是我不能通过视图子类化来做到这一点。这甚至可以访问父母吗？