无法激活约束

Posted 2023-02-23

【中文标题】无法激活约束

【英文标题】：Unable to Activate Constraints

【发布时间】：2019-03-20 23:39:53

【问题描述】：

我收到了错误..

由于未捕获的异常“NSGenericException”而终止应用程序， 原因：'无法使用锚激活约束，因为 他们没有共同的祖先。约束或其锚点是否 不同视图层次结构中的参考项目？这是非法的。'

我参考了其他答案，解决方案始终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。下面是相关代码：

@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)
    ])

【参考方案1】：

替换

refreshActivityIndicatorView.addSubview(activityIndicator)

与

refreshActivityIndicatorView.addSubview(refreshActivityIndicator)

作为崩溃的原因

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 没有作为子视图添加