您可以使用 NSLayoutConstraints 并执行类似的操作。第三行是将进度条放在另一个对象顶部或下方的位置。
var otherObject = UIView()
self.view.addSubview(progressView)
let topConstraint = NSLayoutConstraint(item: progressView, attribute: .topMargin, relatedBy: .equal, toItem: otherObject, attribute: .bottomMargin, multiplier: 1, constant: 0)
let leftConstraint = NSLayoutConstraint(item: progressView, attribute: .leftMargin, relatedBy: .equal, toItem: self.view, attribute: .leftMargin, multiplier: 1, constant: 0)
let rightConstraint = NSLayoutConstraint(item: progressView, attribute: .rightMargin, relatedBy: .equal, toItem: self.view, attribute: .rightMargin, multiplier: 1, constant: 0)
let bottomConstraint = NSLayoutConstraint(item: progressView, attribute: .bottomMargin, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 50)
self.view.addConstraints([topConstraint, leftConstraint, rightConstraint, bottomConstraint])