如何在 Swift 中以编程方式居中 UIActivityIndi​​catorView？

Question

我想以编程方式将活动指示器放置在表视图控制器的中心，但是当我运行代码时，它总是出现在左上角。

这是我的快速代码；

let activityIndicator: UIActivityIndicatorView = {
    let activityIndicator = UIActivityIndicatorView()
    activityIndicator.style = .large
    activityIndicator.hidesWhenStopped = true
    activityIndicator.color = .white
    activityIndicator.startAnimating()
    return activityIndicator
}()

tableView.addSubview(activityIndicator)
    
NSLayoutConstraint.activate([
    activityIndicator.centerXAnchor.constraint(equalTo: tableView.centerXAnchor),
    activityIndicator.centerYAnchor.constraint(equalTo: tableView.centerYAnchor)
])
    
tableView.layoutSubviews()

Answer 1

您需要设置activityIndi​​cator.translatesAutoresizingMaskIntoConstraints = false

  lazy var activityIndicator: UIActivityIndicatorView = {
    let activityIndicator = UIActivityIndicatorView()
    activityIndicator.style = .large
    activityIndicator.translatesAutoresizingMaskIntoConstraints = false
    activityIndicator.hidesWhenStopped = true
    activityIndicator.color = .white
    activityIndicator.startAnimating()
    return activityIndicator
}()

Answer 2

我需要包括该行；

activityIndicator.translatesAutoresizingMaskIntoConstraints = false