ios - 使用 Swift 将 UILabel 动态定位到内容 View 的底部？

Question

我试图将我动态创建的 UILabel 定位到我的 contentView 的底部。我正在使用名为 Fuzi 的 HTML 解析器来捕获 HTML 标签并基于它们创建 UILabel；

func stringFromHTML( _ string: String?)
{
    do{
        let doc = try HTMLDocument(string: string!, encoding: String.Encoding.utf8)
        if let root = doc.body {
            for element in root.children {
                if element.tag == "h2" {
                    // Create new label
                    let label = UILabel()
                    label.text = element.stringValue
                    label.numberOfLines = 0
                    label.font = UIFont(name: "Avenir Next", size: 17)
                    label.textColor = UIColor.black
                    self.contentView.addSubview(label)
                    label.translatesAutoresizingMaskIntoConstraints = false

                    // Label constraints
                    let labelLeading = NSLayoutConstraint(item: label, attribute: .leading, relatedBy: .equal, toItem: contentView, attribute: .leading, multiplier: 1, constant: 20)
                    let labelTrailing = NSLayoutConstraint(item: label, attribute: .trailing, relatedBy: .equal, toItem: contentView, attribute: .trailing, multiplier: 1, constant: -20)
                    let labelTop = NSLayoutConstraint(item: label, attribute: .top, relatedBy: .equal, toItem: contentView, attribute: .top, multiplier: 1, constant: self.contentView.frame.origin.y)

                    self.contentView.addConstraints([labelLeading, labelTrailing, labelTop])

                }
                updateContentViewHeight()
            }
        }

    } 
    catch{
        print("html error\n",error)
    }

}

func updateContentViewHeight(){
    var totalContentHeight:CGFloat = 0.0
    for i in self.contentView.subviews {
        totalContentHeight += i.frame.height
    }
    let contentViewHeight:NSLayoutConstraint = NSLayoutConstraint(item: self.contentView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: totalContentHeight-29)
    self.contentView.addConstraint(contentViewHeight)

}

我尝试在 viewDidAppear 中调用我的 stringFromHTML 函数。但它会将我的 UILabel 定位到很远的地方(它们似乎没有)。

我想把我的标签放在最后一个标签的底部，见下图；

有人可以帮忙吗？提前致谢!

Answer 1

改变

let labelTop = NSLayoutConstraint(item: label, attribute: .top, relatedBy: .equal, toItem: contentView, attribute: .top, multiplier: 1, constant: self.contentView.frame.origin.y)

到

if label != nil {
let labelTop = NSLayoutConstraint(item: label, attribute: .top, relatedBy: .equal, toItem: label[index], attribute: .top, multiplier: 1, constant: 2)
} else {
let labelTop = NSLayoutConstraint(item: label, attribute: .top, relatedBy: .equal, toItem: contentView, attribute: .top, multiplier: 1, constant: self.contentView.frame.origin.y)
}

因为您基本上是在强制每个标签位于相同的 y 位置。