在iOS中将HTML转换为NSAttributedString

Question

我正在使用一个实例UIWebView来处理一些文本并正确地着色它,它将结果作为HTML而不是显示在UIWebView我希望Core Text用a 显示它NSAttributedString.

我能够创建和绘制NSAttributedString但我不确定如何将HTML转换并将HTML映射到属性字符串.

据我所知,在Mac OS X下NSAttributedString有一个initWithHTML:方法,但这只是Mac的补充,不适用于iOS.

我也知道有一个类似的问题,但它没有答案,我虽然我会再试一次,看看是否有人创造了一种方法来做到这一点,如果是的话,他们是否可以分享它.

Answer 1

在iOS 7中,UIKit添加了一个initWithData:options:documentAttributes:error:方法,它可以使用HTML初始化NSAtttributedString,例如:

[[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUTF8StringEncoding] 
                                 options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
                                           NSCharacterEncodingDocumentAttribute: @(NSUTF8StringEncoding)} 
                      documentAttributes:nil error:nil];

在Swift中:

let htmlData = NSString(string: details).data(using: String.Encoding.unicode.rawValue)
let options = [NSAttributedString.DocumentReadingOptionKey.documentType:
        NSAttributedString.DocumentType.html]
let attributedString = try? NSMutableAttributedString(data: htmlData ?? Data(),
                                                          options: options,
                                                          documentAttributes: nil)

Answer 2

Github的Oliver Drobnik正在对NSAttributedString进行一项正在进行的开源添加.它使用NSScanner进行HTML解析.

Answer 3

从HTML创建NSAttributedString必须在主线程上完成!

更新:事实证明,NSAttributedString HTML呈现依赖于WebKit,必须在主线程上运行, 否则偶尔会使用SIGTRAP使应用程序崩溃.

新Relic崩溃日志:

下面是一个更新的线程安全的 Swift 2 String扩展:

extension String {
    func attributedStringFromHTML(completionBlock:NSAttributedString? ->()) {
        guard let data = dataUsingEncoding(NSUTF8StringEncoding) else {
            print("Unable to decode data from html string: \(self)")
            return completionBlock(nil)
        }

        let options = [NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType,
                   NSCharacterEncodingDocumentAttribute: NSNumber(unsignedInteger:NSUTF8StringEncoding)]

        dispatch_async(dispatch_get_main_queue()) {
            if let attributedString = try? NSAttributedString(data: data, options: options, documentAttributes: nil) {
                completionBlock(attributedString)
            } else {
                print("Unable to create attributed string from html string: \(self)")
                completionBlock(nil)
            }
        }
    }
}

用法:

let html = "<center>Here is some <b>HTML</b></center>"
html.attributedStringFromHTML { attString in
    self.bodyLabel.attributedText = attString
}

输出:

Answer 4

NSAttributedString上的Swift初始化程序扩展

我倾向于将此作为一个扩展,NSAttributedString而不是String.我尝试将它作为静态扩展和初始化器.我更喜欢初始化器,这是我在下面包含的内容.

斯威夫特4

internal convenience init?(html: String) {
    guard let data = html.data(using: String.Encoding.utf16, allowLossyConversion: false) else {
        return nil
    }

    guard let attributedString = try?  NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil) else {
        return nil
    }

    self.init(attributedString: attributedString)
}

斯威夫特3

extension NSAttributedString {

internal convenience init?(html: String) {
    guard let data = html.data(using: String.Encoding.utf16, allowLossyConversion: false) else {
        return nil
    }

    guard let attributedString = try? NSMutableAttributedString(data: data, options: [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil) else {
        return nil
    }

    self.init(attributedString: attributedString)
}
}

例

let html = "<b>Hello World!</b>"
let attributedString = NSAttributedString(html: html)

Answer 5

这是一个String用Swift编写的扩展,用于返回HTML字符串NSAttributedString.

extension String {
    func htmlAttributedString() -> NSAttributedString? {
        guard let data = self.dataUsingEncoding(NSUTF16StringEncoding, allowLossyConversion: false) else { return nil }
        guard let html = try? NSMutableAttributedString(data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) else { return nil }
        return html
    }
}

要用,

label.attributedText = "<b>Hello</b> \u{2022} babe".htmlAttributedString()

在上面,我特意添加了一个unicode\u2022来显示它正确呈现unicode.

一个小问题:使用的默认编码NSAttributedString是NSUTF16StringEncoding(不是UTF8!).

Answer 6

对Andrew的解决方案进行了一些修改，并将代码更新为 Swift 3：

此代码现在使用 UITextView 作为self并能够继承其原始字体、字体大小和文本颜色

注意：toHexString()是从这里扩展

extension UITextView {
    func setAttributedStringFromHTML(_ htmlCode: String, completionBlock: @escaping (NSAttributedString?) ->()) {
        let inputText = "\(htmlCode)<style>body { font-family: '\((self.font?.fontName)!)'; font-size:\((self.font?.pointSize)!)px; color: \((self.textColor)!.toHexString()); }</style>"

        guard let data = inputText.data(using: String.Encoding.utf16) else {
            print("Unable to decode data from html string: \(self)")
            return completionBlock(nil)
        }

        DispatchQueue.main.async {
            if let attributedString = try? NSAttributedString(data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) {
                self.attributedText = attributedString
                completionBlock(attributedString)
            } else {
                print("Unable to create attributed string from html string: \(self)")
                completionBlock(nil)
            }
        }
    }
}

用法示例：

mainTextView.setAttributedStringFromHTML("<i>Hello world!</i>") { _ in }

Answer 7

Swift 3.0 Xcode 8版

func htmlAttributedString() -> NSAttributedString? {
    guard let data = self.data(using: String.Encoding.utf16, allowLossyConversion: false) else { return nil }
    guard let html = try? NSMutableAttributedString(data: data, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) else { return nil }
    return html
}

Answer 8

斯威夫特4

• NSAttributedString方便初始化程序
• 没有额外的警卫
• 抛出错误

extension NSAttributedString {

    convenience init(htmlString html: String) throws {
        try self.init(data: Data(html.utf8), options: [
            .documentType: NSAttributedString.DocumentType.html,
            .characterEncoding: String.Encoding.utf8.rawValue
        ], documentAttributes: nil)
    }

}

用法

UILabel.attributedText = try? NSAttributedString(htmlString: "<strong>Hello</strong> World!")