可点击 @、# 标记文本实现

在社交类 APP 中 @、# 符号构成的标记文本已经形成了某种通用的意义：前者表示通知某位好友，而后者表示为某个话题或者分类。这些标记文本一般还都带有高亮显示和可点击的特点。接下来的我会创建一个 UITextView 的子类 AttrTextView 来实现上诉功能。

开始

import UIKit

enum wordType{
    case hashtag   // #标示文本类型
    case mention   // @标示文本类型
}

／/自定义视图用于高亮 # 和 @ 之后的文本（效果类似于微博、twitter），并添加点击事件
class AttrTextView: UITextView {
    var textString: NSString?
    var attrString: NSMutableAttributedString?
    var callBack: ((String,wordType) -> Void)?
    
    ...
}

上码的代码首先声明了一个 wordType 的枚举类型，该类用用于对标示文本进行类型标记。接着我们定义了自定义类型 AttrTextView，并且声明了三个属性。textString 表示原文本，attrString 进行属性设置后的文本，callBack 为 # 和 @ 标记文本的点击事件回调。

文本设置

定义好属性后，我们就需要考虑使用接口的实现了。正常情况下文本应该有以下属性需要设置：常规文本的字体、颜色；# 和 @ 标记文本各自对应的字体和颜色；点击事件设置以及回调函数。代码如下：

public func setText(text: String,normalColor: UIColor,hashtagColor: UIColor,mentionColor: UIColor,normalFont: UIFont,hashTagFont: UIFont,mentionFont: UIFont,tapCallBack callBack: @escaping (String,wordType) -> Void) {
    self.callBack = callBack
    self.attrString = NSMutableAttributedString(string: text)
    self.textString = NSString(string: text)
    
    // Set initial font attributes for our string
    // 设置字体和文本颜色
    attrString?.addAttribute(NSFontAttributeName,value: normalFont,range: NSRange(location: 0,length: (textString?.length)!))
    attrString?.addAttribute(NSForegroundColorAttributeName,value: normalColor,length: (textString?.length)!))
    
    // Call a custom set Hashtag and Mention Attributes Function
    // 设置 #、@ 的高亮色等属性
    setAttrWithName(attrName: "Hashtag",wordPrefix: "#",color: hashtagColor,text: text,font: hashTagFont)
    setAttrWithName(attrName: "Mention",wordPrefix: "@",color: mentionColor,font: mentionFont)
    
    // Add tap gesture that calls a function tapRecognized when tapped
    // 添加手势
    let tapper = UITapGestureRecognizer(target: self,action: #selector(self.tapRecognized(tapGesture:)))
    addGestureRecognizer(tapper)
}

上面代码中的 setAttrWithName 函数的目的是对 #、@ 标记文本的属性进行设置，代码如下：

private func setAttrWithName(attrName: String,wordPrefix: String,color: UIColor,text: String,font: UIFont) {
    // Words can be separated by either a space or a line break
    // 将文本按照空格和 n 键拆分为单词数组
    var words: [String] = []
    let wordtext: [String] = text.components(separatedBy: " ")
    for var word in wordtext {
        
        if word.hasPrefix("n") {
            word = word.replacingOccurrences(of: "n",with: "")
        }
        words.append(word)
        
    }
    
    // 便利数组，检查是否满足条件并进行属性设置
    for word in words.filter({$0.hasPrefix(wordPrefix)}) {
        let range = textString!.range(of: word)
        attrString?.addAttribute(NSForegroundColorAttributeName,value: color,range: range)
        attrString?.addAttribute(attrName,value: 1,range: range)
        attrString?.addAttribute("Clickable",range: range)
        attrString?.addAttribute(NSFontAttributeName,value: font,range: range)
    }
    self.attributedText = attrString
}

点击事件的处理

文本点击的处理稍微有点麻烦，需要考虑多种情况：

• 没有点击在任何文本上

• 点击在普通文本

• 点击在标示文本，并且需要识别标示文本的类型

func tapRecognized(tapGesture: UITapGestureRecognizer) {
    var wordString: String?         // The String value of the word to pass into callback function
    var char: NSAttributedString!   //The character the user clicks on. It is non optional because if the user clicks on nothing,char will be a space or " "
    var word: NSAttributedString?   //The word the user clicks on
    var isHashtag: AnyObject?
    var isAtMention: AnyObject?
        
    // Gets the range of the character at the place the user taps
    // 检查用户点击字符的范围
    let point = tapGesture.location(in: self)
    let charPosition = closestPosition(to: point)
        
        
    guard let charRange = tokenizer.rangeEnclosingPosition(charPosition!,with: .character,inDirection: 1) else {
        return
    }
        
    let location = offset(from: beginningOfDocument,to: charRange.start)
    let length = offset(from: charRange.start,to: charRange.end)
    let attrRange = NSMakeRange(location,length)
    char = attributedText.attributedSubstring(from: attrRange)
        
    // If the user has not clicked on anything,exit the function
    if char.string == " "{
        print("User clicked on nothing")
        return
    }
        
    // Checks the character's attribute,if any
    // 检查属性标示
    isHashtag = char?.attribute("Hashtag",at: 0,longestEffectiveRange: nil,in: NSMakeRange(0,char!.length)) as AnyObject?
    isAtMention = char?.attribute("Mention",char!.length)) as AnyObject?
        
        
        
    // Gets the range of the word at the place user taps
    // 获得点击单词的范围
    let wordRange = tokenizer.rangeEnclosingPosition(charPosition!,with: .word,inDirection: 1)
        
        
    /*
    单词的范围在下面两种情况下为 nil:
    1. 点击在 "#" or "@" 标示上
    2. 没有点击在任何字符上。但是这种情况在上面的代码中已经排除了，所有只剩下 1
    */
    if wordRange != nil {
        let wordLocation = offset(from: beginningOfDocument,to: wordRange!.start)
        let wordLength = offset(from: wordRange!.start,to: wordRange!.end)
        let wordAttrRange = NSMakeRange(wordLocation,wordLength)
        word = attributedText.attributedSubstring(from: wordAttrRange)
        wordString = word!.string
    } else {
        /*
        右移12像素后再获取单词
        */
        var modifiedPoint = point
         modifiedPoint.x += 12
        let modifiedPosition = closestPosition(to: modifiedPoint)
        let modifedWordRange = tokenizer.rangeEnclosingPosition(modifiedPosition!,inDirection: 1)
        if modifedWordRange != nil {
            let wordLocation = offset(from: beginningOfDocument,to: modifedWordRange!.start)
            let wordLength = offset(from: modifedWordRange!.start,to: modifedWordRange!.end)
            let wordAttrRange = NSMakeRange(wordLocation,wordLength)
            word = attributedText.attributedSubstring(from: wordAttrRange)
            wordString = word!.string
        }
    }
        
    if let stringToPass = wordString {
        // 点击回掉函数
        if isHashtag != nil && callBack != nil {
            callBack!(stringToPass,wordType.hashtag)
        } else if isAtMention != nil && callBack != nil {
            callBack!(stringToPass,wordType.mention)
        }
    }
}

上面的代码处理中，首先使用 .character 检查点击位置的字符，并对无效区域的点击进行了处理。这里之所以使用 .character 而不是后面的 .word 的原因是：后者会将 @、# 这些标示符丢弃，导致一只类似点击到无效区域的情形。当上诉检查通过也就是点击区域有效的时候，我们使用 .word，获取点击区域的单词。为了应对前面标示点击的情形，当区域无效的时候，我们右移12个像素后再获取单词。最后我们根据文本不同类型进行对应处理。

最后

最后我们看一下简单使用示例代码：

let attrView = AttrTextView.init(frame: CGRect.init(x: 0,y: 64,width: view.bounds.size.width,height: view.bounds.size.height - 64),textContainer: nil)
    self.view.addSubview(attrView)
      
attrView.setText(text: "#PHP 是不是世界上最好的语言？ @all ",normalColor: .black,hashtagColor: .red,mentionColor: .blue,normalFont: UIFont.systemFont(ofSize: 10),hashTagFont:  UIFont.systemFont(ofSize: 14),mentionFont:  UIFont.systemFont(ofSize: 14)) { word,wordType in
    print(word)
}

（编辑：李大同）

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