两个具有不同字体大小的自动布局UILabels :文本顶部对齐

let label1 = UILabel()
label1.text = "Label 1"
label1.font = UIFont.systemFont(ofSize: 20)

let label2 = UILabel()
label2.text = "Label 2"
label2.font = UIFont.systemFont(ofSize: 16)

let containerView = UIView()
containerView.addSubview(label1)
containerView.addSubview(label2)

label1.translatesAutoresizingMaskIntoConstraints = false
label2.translatesAutoresizingMaskIntoConstraints = false

// 设置label1的顶部约束
let topConstraint = NSLayoutConstraint(item: label1, attribute: .top, relatedBy: .equal, toItem: containerView, attribute: .top, multiplier: 1, constant: 0)

// 设置label2的顶部约束
let bottomConstraint = NSLayoutConstraint(item: label2, attribute: .top, relatedBy: .equal, toItem: label1, attribute: .bottom, multiplier: 1, constant: 0)

// 添加约束到父视图
containerView.addConstraints([topConstraint, bottomConstraint])

view.addSubview(containerView)

// 设置containerView的约束，例如左边距和宽度
containerView.translatesAutoresizingMaskIntoConstraints = false
let leadingConstraint = NSLayoutConstraint(item: containerView, attribute: .leading, relatedBy: .equal, toItem: view, attribute: .leading, multiplier: 1, constant: 20)
let widthConstraint = NSLayoutConstraint(item: containerView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 200)

view.addConstraints([leadingConstraint, widthConstraint])

// 更新布局
view.layoutIfNeeded()