ios - 以编程方式添加 View 的问题

Question

嗨，我正在以编程方式添加一些像这样的 View

        let xPos = (self.view.frame.size.width - 200)/2
        self.headerLabel = UILabel(frame: CGRect(x: xPos, y: 50.0, width: 200.0, height: 100.0))
        self.shopButton = UIButton(frame: CGRect(x: xPos, y: 150.0, width: 200.0, height: 40.0))
        self.createButton = UIButton(frame: CGRect(x: xPos, y: 230.0, width: 200.0, height: 40.0))
        self.orLabel = UILabel(frame: CGRect(x: xPos, y: 200.0, width: 200.0, height: 20.0))

问题是当我将设备旋转到横向模式时，反之亦然，我的 View 与左侧对齐。我该如何预防？

Answer 1

使用NSLayoutContaint将 View 中的约束添加到其 super View

例如

let horizontalConstraint = NSLayoutConstraint.init(item: view, attribute: .centerX, relatedBy: .equal, toItem: view.superview, attribute: .centerX, multiplier: 1, constant: 1)
        horizontalConstraint.isActive = true

        let verticalConstraint = NSLayoutConstraint.init(item: view, attribute: .centerY, relatedBy: .equal, toItem: view.superview, attribute: .centerY, multiplier: 1, constant: 1)
        verticalConstraint.isActive = true