根据内容检测文本方向

Question

我想知道是否可以根据内容动态设置UITextView的文字方向？

默认行为是这样的：如果您使用LTR语言开始一行该行将是LTR，但如果您使用RTL语言开始下一行该行的方向将更改为RTL。

我想要的是根据第一个设置整个段落的方向。

有可能吗？

Answer 1

我自己也遇到过这个问题。通过一点点搜索，为UITextView制作了这个扩展，它可以检测第一个字母的语言，并在需要时进行RTL。 您需要在设置文本后调用该函数，因此您可能希望在UITextViewDelegate文本更改“方法中调用它。

extension UITextView {
func detectRightToLeft() {
    if let text = self.text where !text.isEmpty {
        let tagschemes = NSArray(objects: NSLinguisticTagSchemeLanguage)
        let tagger = NSLinguisticTagger(tagSchemes: tagschemes as! [String], options: 0)
        tagger.string = text

        let language = tagger.tagAtIndex(0, scheme: NSLinguisticTagSchemeLanguage, tokenRange: nil, sentenceRange: nil)
        if language?.rangeOfString("he") != nil || language?.rangeOfString("ar") != nil || language?.rangeOfString("fa") != nil {
            self.text = text.stringByReplacingOccurrencesOfString("\n", withString: "\n")
            self.textAlignment = .Right
            self.makeTextWritingDirectionRightToLeft(nil)
        }else{
            self.textAlignment = .Left
            self.makeTextWritingDirectionLeftToRight(nil)
        }
    }
}
}

当然这很混乱而且并不完美。但它对我有用。你可以得到这个想法。

斯威夫特3：

extension UITextView {
    func detectRightToLeft() {
        if let text = self.text, !text.isEmpty {
            let tagschemes = NSArray(objects: NSLinguisticTagSchemeLanguage)
            let tagger = NSLinguisticTagger(tagSchemes: tagschemes as! [String], options: 0)
            tagger.string = text

            let language = tagger.tag(at: 0, scheme: NSLinguisticTagSchemeLanguage, tokenRange: nil, sentenceRange: nil)
            if language?.range(of: "he") != nil || language?.range(of: "ar") != nil || language?.range(of: "fa") != nil {
                self.text = text.replacingOccurrences(of: "\n", with: "\n")
                self.textAlignment = .right
                self.makeTextWritingDirectionRightToLeft(nil)
            }else{
                self.textAlignment = .left
                self.makeTextWritingDirectionLeftToRight(nil)
            }
        }
    }
}

Answer 2

基于Arash R的出色答案，这是一个Swift 4.2扩展，可以为UITextView中的每个段落分别选择文本方向。

它确定每个段落中最后一个字符的语言。这样，如果您使用RTL语言编号列表，则该段落将为RTL。

从文本更改方法中调用该函数，如果在第一次从ViewDidLoad中加载ViewController时填充了UITextView，则调用该函数。

extension UITextView {
    func detectRightToLeft() {
        if let text = self.text, !text.isEmpty { // Set text, make sure it is not nil
            let cleanFile = text.replacingOccurrences(of: "\r", with: "\n")
            var newLineIndices:Array<Int> = []
            for (index, char) in cleanFile.enumerated() {
                if char == "\n" {
                    newLineIndices.append(index) // Get location of all newline characters
                }
            }
            newLineIndices.insert(-1, at: 0) // Place position 0 at the beginning of the array
            newLineIndices.append(cleanFile.count) // Add the location after last character

            let tagschemes = NSArray(objects: NSLinguisticTagScheme.language)
            let tagger = NSLinguisticTagger(tagSchemes: tagschemes as! [NSLinguisticTagScheme], options: 0)
            tagger.string = cleanFile

            for i in 0..<newLineIndices.count-1 {
                // Determine direction by the last character of paragraph
                var taggerCounter = newLineIndices[i+1]-1
                var language = tagger.tag(at: taggerCounter, scheme: NSLinguisticTagScheme.language, tokenRange: nil, sentenceRange: nil)
                // Neutral characters should make the tagger look at the character before
                while language == nil && taggerCounter >= 1 {
                    taggerCounter -= 1
                    language = tagger.tag(at: taggerCounter, scheme: NSLinguisticTagScheme.language, tokenRange: nil, sentenceRange: nil)
                }

                if String(describing: language).range(of: "he") != nil || String(describing: language).range(of: "ar") != nil || String(describing: language).range(of: "fa") != nil {
                    self.setBaseWritingDirection(.rightToLeft, for: self.textRange(from: self.position(from: self.beginningOfDocument, offset: newLineIndices[i]+1)!, to: self.position(from: self.beginningOfDocument, offset: newLineIndices[i+1])!)!)
                    print ("Right to Left Paragraph at character \(newLineIndices[i]+1)")

                } else {
                    self.setBaseWritingDirection(.leftToRight, for: self.textRange(from: self.position(from: self.beginningOfDocument, offset: newLineIndices[i]+1)!, to: self.position(from: self.beginningOfDocument, offset: newLineIndices[i+1])!)!)
                    print ("Left to Right Paragraph at character \(newLineIndices[i]+1)")
                }
            }
        }
    }
}

编辑：先前版本包含一个选项，可以按段落的第一个字符进行选择。该选项导致崩溃，因此我暂时将其省略。而是，当前代码包括对中性字符的处理。另一个编辑：将taggerCounter最小值更改为1，以防止其变为负数。

Answer 3

基于罗恩的答案，这是字符串的更通用扩展名

extension String {

    var isRTL: Bool {
        let cleanFile = self.replacingOccurrences(of: "\r", with: "\n")
        var newLineIndices: Array<Int> = []

        for (index, char) in cleanFile.enumerated() {
            if char == "\n" {
                newLineIndices.append(index)
            }
        }

        newLineIndices.insert(-1, at: 0)
        newLineIndices.append(cleanFile.count)

        let tagschemes = NSArray(objects: NSLinguisticTagScheme.language)
        let tagger = NSLinguisticTagger(tagSchemes: tagschemes as! [NSLinguisticTagScheme], options: 0)
        tagger.string = cleanFile

        for i in 0..<newLineIndices.count - 1 {
            let language = tagger.tag(at: newLineIndices[i + 1] - 1, scheme: NSLinguisticTagScheme.language, tokenRange: nil, sentenceRange: nil)

            if String(describing: language).range(of: "he") != nil || String(describing: language).range(of: "ar") != nil || String(describing: language).range(of: "fa") != nil {
                return true
            } else {
                return false
            }
        }

        return false
    }

    var isLTR: Bool {
        let cleanFile = self.replacingOccurrences(of: "\r", with: "\n")
        var newLineIndices: Array<Int> = []

        for (index, char) in cleanFile.enumerated() {
            if char == "\n" {
                newLineIndices.append(index)
            }
        }

        newLineIndices.insert(-1, at: 0)
        newLineIndices.append(cleanFile.count)

        let tagschemes = NSArray(objects: NSLinguisticTagScheme.language)
        let tagger = NSLinguisticTagger(tagSchemes: tagschemes as! [NSLinguisticTagScheme], options: 0)
        tagger.string = cleanFile

        for i in 0..<newLineIndices.count - 1 {
            let language = tagger.tag(at: newLineIndices[i + 1] - 1, scheme: NSLinguisticTagScheme.language, tokenRange: nil, sentenceRange: nil)

            if String(describing: language).range(of: "he") != nil || String(describing: language).range(of: "ar") != nil || String(describing: language).range(of: "fa") != nil {
                return false
            } else {
                return true
            }
        }

        return false
    }

}