你好我正在尝试以编程方式创建一个标签并添加 NSLayoutConstraints 以便它在 super View 中居中,而不管屏幕大小和方向等。我已经看过但找不到可遵循的示例。这是我所拥有的:
let codedLabel:UILabel = UILabel()
codedLabel.frame = CGRect(x: 100, y: 100, width: 200, height: 200)
codedLabel.textAlignment = .center
codedLabel.text = alertText
codedLabel.numberOfLines=1
codedLabel.textColor=UIColor.red
codedLabel.font=UIFont.systemFont(ofSize: 22)
codedLabel.backgroundColor=UIColor.lightGray
let heightConstraint:NSLayoutConstraint = NSLayoutConstraint(item: codedLabel, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 200)
let widthConstraint:NSLayoutConstraint = NSLayoutConstraint(item: codedLabel, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 200)
codedLabel.addConstraints([heightConstraint, widthConstraint])
let verticalConstraint:NSLayoutConstraint = NSLayoutConstraint(item: codedLabel, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: self.contentView, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0)
let horizontalConstraint:NSLayoutConstraint = NSLayoutConstraint(item: codedLabel, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: self.contentView, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0)
self.contentView.addConstraints([verticalConstraint, horizontalConstraint])
self.contentView.addSubview(codedLabel)
最佳答案
NSLayoutAnchor是 iOS 9 中的新功能,它极大地清理了约束语法。
let codedLabel:UILabel = UILabel()
codedLabel.frame = CGRect(x: 100, y: 100, width: 200, height: 200)
codedLabel.textAlignment = .center
codedLabel.text = alertText
codedLabel.numberOfLines=1
codedLabel.textColor=UIColor.red
codedLabel.font=UIFont.systemFont(ofSize: 22)
codedLabel.backgroundColor=UIColor.lightGray
self.contentView.addSubview(codedLabel)
codedLabel.translatesAutoresizingMaskIntoConstraints = false
codedLabel.heightAnchor.constraint(equalToConstant: 200).isActive = true
codedLabel.widthAnchor.constraint(equalToConstant: 200).isActive = true
codedLabel.centerXAnchor.constraint(equalTo: codedLabel.superview!.centerXAnchor).isActive = true
codedLabel.centerYAnchor.constraint(equalTo: codedLabel.superview!.centerYAnchor).isActive = true
关于ios - Swift 3 以编程方式创建 UILabel 并添加 NSLayoutConstraints,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40299190/