如何动态计算具有行间距的nsattributed字符串的高度

Question

我正在尝试计算具有 LineSpacing 属性的 UILabel 的高度。奇怪的是，正常 label.text 的高度计算值低于 label.attributedText 及其行高。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SO编写的，简洁明了，在我的项目中实现不同。

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 getHeightWithGivenWidthAndLineHeight(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
    }

我称之为

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

使用普通字符串（无间距）效果很好，当我将 attributedstring 与 lineSpacing 一起使用时，它无法计算出正确的值。

Answer 1

您可以只使用 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)

已添加到您的扩展中的 attributedString 代码，如果您需要查看：

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
    }

Answer 2

我以这种方式更新了我的扩展，以同时设置行高和 return 新标签高度。感谢 beyowulf

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
    }
}

如何动态计算具有行间距的nsattributed字符串的高度

How to calculate height of nsattributed string with line spacing dynamically

nsattributedstring

ios

swift