Swift-更改具有自己样式的HTML字符串上的字体

Question

我正在从Wordpress API获取HTML字符串并将其解析为Attributed String以在我的应用程序中显示它.由于字符串有自己的样式,它会显示不同的字体和大小,这会影响我们的设计选择.

我想要做的是在整个属性字符串上更改字体及其大小.

我尝试在属性字符串的选项中这样做,但它什么也没做:

let attributedT = try! NSAttributedString(
            data: nContent!.decodeHTML().data(using: String.Encoding.unicode, allowLossyConversion: true)!,
            options: [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSFontAttributeName: UIFont(name: "Helvetica", size: 16.0)!],
            documentAttributes: nil)
        contentLbl.attributedText = attributedT

有没有人对如何实现这一点有任何想法？

PS我知道我可以在字符串的开头或结尾添加一个CSS标签,但这会覆盖其中的其他样式吗？此外,如果这是一个有效的解决方案,您能否提供一个如何做的样本？

Answer 1

基本上,您要做的是将NSAttributedString转换为NSMutableAttributedString.

let attributedT = // ... attributed string
let mutableT = NSMutableAttributedString(attributedString:attributedT)

现在,您可以调用addAttributes在任何所需范围内应用属性,例如不同的字体,例如整个事物.

然而,不幸的是,没有象征性特征的字体(例如斜体)是与具有该符号特征的字体不同的字体.因此,您将需要一个从字体复制现有符号特征并将其应用于另一种字体的实用程序:

func applyTraitsFromFont(_ f1: UIFont, to f2: UIFont) -> UIFont? {
    let t = f1.fontDescriptor.symbolicTraits
    if let fd = f2.fontDescriptor.withSymbolicTraits(t) {
        return UIFont.init(descriptor: fd, size: 0)
    }
    return nil
}

好吧,所以,有了这个实用程序,让我们试一试.我将从一些简单的HTML开始,并将其转换为属性字符串,就像您正在做的那样:

let html = "<p>Hello <i>world</i>, hello</p>"
let data = html.data(using: .utf8)!
let att = try! NSAttributedString.init(
    data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
    documentAttributes: nil)
let matt = NSMutableAttributedString(attributedString:att)

如您所见,我已经转换为NSMutableAttributedString,正如我所建议的那样.现在我将循环通过样式运行字体,在使用我的实用程序应用现有特征时更改为不同的字体:

matt.enumerateAttribute(
    NSFontAttributeName,
    in:NSMakeRange(0,matt.length),
    options:.longestEffectiveRangeNotRequired) { value, range, stop in
        let f1 = value as! UIFont
        let f2 = UIFont(name:"Georgia", size:20)!
        if let f3 = applyTraitsFromFont(f1, to:f2) {
            matt.addAttribute(
                NSFontAttributeName, value:f3, range:range)
        }
    }

这是结果:

显然,您可以根据您的设计需求调整此过程,使其更加复杂.

Answer 2

Swift 4解决方案

• NSAttributedString 使用便利初始化程序扩展
• 枚举通过属性字符串(HTML文档)字体属性,并替换为提供的 UIFont
• 保留原始HTML字体大小,或使用提供的UIFont@see useDocumentFontSize参数的字体大小
• 这个方法可以简单地将HTML转换为NSAttributedString,而无需使用字体进行操作的重载,只需跳过font参数,@ see guard语句

extension NSAttributedString {

    convenience init(htmlString html: String, font: UIFont? = nil, useDocumentFontSize: Bool = true) throws {
        let options: [NSAttributedString.DocumentReadingOptionKey : Any] = [
            .documentType: NSAttributedString.DocumentType.html,
            .characterEncoding: String.Encoding.utf8.rawValue
        ]

        let data = html.data(using: .utf8, allowLossyConversion: true)
        guard (data != nil), let fontFamily = font?.familyName, let attr = try? NSMutableAttributedString(data: data!, options: options, documentAttributes: nil) else {
            try self.init(data: data ?? Data(html.utf8), options: options, documentAttributes: nil)
            return
        }

        let fontSize: CGFloat? = useDocumentFontSize ? nil : font!.pointSize
        let range = NSRange(location: 0, length: attr.length)
        attr.enumerateAttribute(.font, in: range, options: .longestEffectiveRangeNotRequired) { attrib, range, _ in
            if let htmlFont = attrib as? UIFont {
                let traits = htmlFont.fontDescriptor.symbolicTraits
                var descrip = htmlFont.fontDescriptor.withFamily(fontFamily)

                if (traits.rawValue & UIFontDescriptorSymbolicTraits.traitBold.rawValue) != 0 {
                    descrip = descrip.withSymbolicTraits(.traitBold)!
                }

                if (traits.rawValue & UIFontDescriptorSymbolicTraits.traitItalic.rawValue) != 0 {
                    descrip = descrip.withSymbolicTraits(.traitItalic)!
                }

                attr.addAttribute(.font, value: UIFont(descriptor: descrip, size: fontSize ?? htmlFont.pointSize), range: range)
            }
        }

        self.init(attributedString: attr)
    }

}

用法-1(替换字体)

let attr = try? NSAttributedString(htmlString: "<strong>Hello</strong> World!", font: UIFont.systemFont(ofSize: 34, weight: .thin))

用法-2(NSMutableAttributedString示例)

let attr = try! NSMutableAttributedString(htmlString: "<strong>Hello</strong> World!", font: UIFont.systemFont(ofSize: 34, weight: .thin))
attr.append(NSAttributedString(string: " MINIMIZE", attributes: [.link: "@m"]))

用法-3(仅将HTML转换为NSAttributedString)

let attr = try? NSAttributedString(htmlString: "<strong>Hello</strong> World!")

Answer 3

setAttributes将重置HTML中的所有属性.我写了一个扩展方法来避免这种情况:

斯威夫特4

public convenience init?(HTMLString html: String, font: UIFont? = nil) throws {
    let options : [NSAttributedString.DocumentReadingOptionKey : Any] =
        [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html,
         NSAttributedString.DocumentReadingOptionKey.characterEncoding: String.Encoding.utf8.rawValue]

    guard let data = html.data(using: .utf8, allowLossyConversion: true) else {
        throw NSError(domain: "Parse Error", code: 0, userInfo: nil)
    }

    if let font = font {
        guard let attr = try? NSMutableAttributedString(data: data, options: options, documentAttributes: nil) else {
            throw NSError(domain: "Parse Error", code: 0, userInfo: nil)
        }
        var attrs = attr.attributes(at: 0, effectiveRange: nil)
        attrs[NSAttributedStringKey.font] = font
        attr.setAttributes(attrs, range: NSRange(location: 0, length: attr.length))
        self.init(attributedString: attr)
    } else {
        try? self.init(data: data, options: options, documentAttributes: nil)
    }
}

测试样本:

let html = "<html><body><h1 style=\"color:red;\">html text here</h1></body></html>"
let font = UIFont.systemFont(ofSize: 16)

var attr = try NSMutableAttributedString(HTMLString: html, font: nil)
var attrs = attr?.attributes(at: 0, effectiveRange: nil)
attrs?[NSAttributedStringKey.font] as? UIFont
// print: <UICTFont: 0x7ff19fd0a530> font-family: "TimesNewRomanPS-BoldMT"; font-weight: bold; font-style: normal; font-size: 24.00pt

attr = try NSMutableAttributedString(HTMLString: html, font: font)
attrs = attr?.attributes(at: 0, effectiveRange: nil)
attrs?[NSAttributedStringKey.font] as? UIFont
// print: <UICTFont: 0x7f8c0cc04620> font-family: ".SFUIText"; font-weight: normal; font-style: normal; font-size: 16.00pt

Answer 4

我以前的（Swift 4）解决方案的Swift 3版本

extension NSAttributedString {

    convenience init(htmlString html: String, font: UIFont? = nil, useDocumentFontSize: Bool = true) throws {
        let options: [String : Any] = [
            NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
            NSCharacterEncodingDocumentAttribute: String.Encoding.utf8.rawValue
        ]

        let data = html.data(using: .utf8, allowLossyConversion: true)
        guard (data != nil), let fontFamily = font?.familyName, let attr = try? NSMutableAttributedString(data: data!, options: options, documentAttributes: nil) else {
            try self.init(data: data ?? Data(html.utf8), options: options, documentAttributes: nil)
            return
        }

        let fontSize: CGFloat? = useDocumentFontSize ? nil : font!.pointSize
        let range = NSRange(location: 0, length: attr.length)
        attr.enumerateAttribute(NSFontAttributeName, in: range, options: .longestEffectiveRangeNotRequired) { attrib, range, _ in
            if let htmlFont = attrib as? UIFont {
                let traits = htmlFont.fontDescriptor.symbolicTraits
                var descrip = htmlFont.fontDescriptor.withFamily(fontFamily)

                if (traits.rawValue & UIFontDescriptorSymbolicTraits.traitBold.rawValue) != 0 {
                    descrip = descrip.withSymbolicTraits(.traitBold)!
                }

                if (traits.rawValue & UIFontDescriptorSymbolicTraits.traitItalic.rawValue) != 0 {
                    descrip = descrip.withSymbolicTraits(.traitItalic)!
                }

                attr.addAttribute(NSFontAttributeName, value: UIFont(descriptor: descrip, size: fontSize ?? htmlFont.pointSize), range: range)
            }
        }

        self.init(attributedString: attr)
    }

}