无法激活约束

Question

我收到错误..

Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to activate constraint with anchors because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.'

我参考了其他答案，解决方案一直是在以编程方式激活约束之前在 viewDidLoad 中添加子视图。

我仍然收到同样的崩溃，但不明白是什么原因造成的。任何指导将不胜感激。以下是相关代码：

@IBOutlet weak var activityIndicatorView: UIView!
@IBOutlet weak var refreshActivityIndicatorView: UIView!

let activityIndicator = AnimationView(name: "name")
let refreshActivityIndicator = AnimationView(name: "name")

override func viewDidLoad() {
    super.viewDidLoad()
    activityIndicatorView.addSubview(activityIndicator)
    activityIndicator.translatesAutoresizingMaskIntoConstraints = false
    refreshActivityIndicatorView.addSubview(activityIndicator)
    refreshActivityIndicator.translatesAutoresizingMaskIntoConstraints = false

    NSLayoutConstraint.activate([
        activityIndicator.centerXAnchor.constraint(equalTo: activityIndicatorView.centerXAnchor),
        activityIndicator.centerYAnchor.constraint(equalTo: activityIndicatorView.centerYAnchor),
        activityIndicator.widthAnchor.constraint(equalToConstant: activityIndicatorView.frame.width),
        activityIndicator.heightAnchor.constraint(equalToConstant: activityIndicatorView.frame.height),
        refreshActivityIndicator.centerXAnchor.constraint(equalTo: refreshActivityIndicatorView.centerXAnchor),
        refreshActivityIndicator.centerYAnchor.constraint(equalTo: refreshActivityIndicatorView.centerYAnchor),

    refreshActivityIndicator.widthAnchor.constraint(equalToConstant: refreshActivityIndicatorView.frame.width),

    refreshActivityIndicator.heightAnchor.constraint(equalToConstant: refreshActivityIndicatorView.frame.height)
    ])
}

Answer 1

替换

refreshActivityIndicatorView.addSubview(activityIndicator)

和

refreshActivityIndicatorView.addSubview(refreshActivityIndicator)

崩溃的原因

refreshActivityIndicator.centerXAnchor.constraint(equalTo: refreshActivityIndicatorView.centerXAnchor),
refreshActivityIndicator.centerYAnchor.constraint(equalTo: refreshActivityIndicatorView.centerYAnchor), 
refreshActivityIndicator.widthAnchor.constraint(equalToConstant: refreshActivityIndicatorView.frame.width), 
refreshActivityIndicator.heightAnchor.constraint(equalToConstant: refreshActivityIndicatorView.frame.height)

您在 refreshActivityIndicatorView 和 refreshActivityIndicator 之间设置了约束，而 refreshActivityIndicator 未添加为子视图

无法激活约束

Unable to Activate Constraints

constraints

ios

nslayoutconstraint

swift