Ios 如何用行距动态计算NSA指定字符串的高度

我正在尝试使用“线间距”属性计算UILabel的高度。奇怪的是，正常label.text的高度计算值低于label.AttributeText及其线宽。看起来我做错了什么，但找不到什么，所以请帮忙：D

提供的代码是专门为使其紧凑和清晰而设计的，在我的项目中以不同的方式实现

extension NSAttributedString {
    func heightWithWidth(width: CGFloat) -> CGFloat {
        let maxSize = CGSize(width: width, height: CGFloat.max)

        let boundingBox = self.boundingRectWithSize(maxSize, options: [.UsesLineFragmentOrigin, .UsesFontLeading, .UsesDeviceMetrics], context: nil)

        return boundingBox.height
    }
}

extension UILabel {

    func getHeightWidthGivenWidthAndLineHeight(lineHeight: CGFloat, labelWidth: CGFloat) -> CGFloat {
        let text = self.text
        if let text = text {
            let attributeString = NSMutableAttributedString(string: text)
            let style = NSMutableParagraphStyle()

            style.lineSpacing = lineHeight
            attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
            let height = attributeString.heightWithWidth(labelWidth)
            self.attributedText = attributeString
            return height
        }
        return 0
    }

我把这个叫做

let contentHeight = contentLabel.text! == "" ? 0 : contentLabel.getHeightWidthGivenWidthAndLineHeight(3, labelWidth: labelWidth)

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当我使用attributedstring和lineSpacing时，使用普通字符串（不带间距）非常有效。如果无法计算正确的值。

您可以使用UILabel的sizeThatFits。例如：

    let text = "This is\nSome\nGreat\nText"

    let contentHeight = contentLabel.text! == "" ? 0 : contentLabel.getHeightWidthGivenWidthAndLineHeight(6, labelWidth: labelWidth) 
    //returns 73.2

但只是设置

    contentLabel.attributedText = contentLabel.attributedString //attributedString is same as getHeightWidthGivenWidthAndLineHeight

    let size = contentLabel.sizeThatFits(contentLabel.frame.size) 
    //returns (w 49.5,h 99.5)

添加到扩展名的attributedString代码，如果需要查看：

var attributedString:NSAttributedString?{
        if let text = self.text{
            let attributeString = NSMutableAttributedString(string: text)
            let style = NSMutableParagraphStyle()

            style.lineSpacing = 6
            attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
            return attributeString
        }
        return nil
    }

---

我用这种方式更新了扩展名，以设置行高度，同时返回新标签高度。桑克斯到贝奥武夫

extension UILabel {

    func setLineHeight(lineHeight: CGFloat, labelWidth: CGFloat) -> CGFloat {
        let text = self.text
        if let text = text {
            let attributeString = NSMutableAttributedString(string: text)
            let style = NSMutableParagraphStyle()

            style.lineSpacing = lineHeight
            attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
            self.attributedText = attributeString
            return self.sizeThatFits(CGSize(width: labelWidth, height: 20)).height
        }
        return 0
    }
}

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Thanx不知道SizeThatFits（）是这样工作的：）。我使用SizeThatFits（）更新扩展名以设置行高度并返回uilabel所需的高度