在掌阅APP阅读小说时，会出现长按文字划线的功能，自己琢磨了一下，总结一下。

0.效果图

Dec-20-2018 14-34-01.gif

1.添加长按手势

    override init(frame: CGRect) {
    super.init(frame: frame)
    
    backgroundColor = UIColor.white
    
    if longPress == nil {
        longPress = UILongPressGestureRecognizer(target: self, action: #selector(longPressAction(longGesture:)))
        addGestureRecognizer(longPress)
    }
    
    let tapGesture = UITapGestureRecognizer(target: self, action: #selector(tapAction))
    addGestureRecognizer(tapGesture)
}

2.在长按手势的方法里面获取到选中的range以及对应的rect，并刷新界面UI

• 首先根据点击位置，获取到点击位置及其相邻位置的两个点的range；
• 将获取到的range转换成对应的frame坐标；
• 手势滑动时，更新range的位置和对应的frame；
• 保存手势最初位置的rang，以便于手势移动的更新range的位置；
• 根据frame绘制界面；

    @objc func longPressAction(longGesture: UILongPressGestureRecognizer) {
    var originPoint = CGPoint.zero
    switch longPress.state {
    case .began:
        print("longPress-Began")
        
        originPoint = longGesture.location(in: self)
        originRange = getTouchLocationRange(point: originPoint)
        rects = getRangeRects(range: selectedRange, ctframe: ctFrame)
        selectedRange = originRange
        setNeedsDisplay()
        
    case .changed:
        
        let finalRange = getTouchLocationRange(point: longGesture.location(in: self))
        if finalRange.location == 0 || finalRange.location == NSNotFound {
            return
        }
        var range = NSRange(location: 0, length: 0)
        range.location = min(finalRange.location, originRange.location)
        if finalRange.location > originRange.location {
            range.length = finalRange.location - originRange.location + finalRange.length
        } else {
            range.length = originRange.location - finalRange.location + originRange.length
        }
 
        selectedRange = range
        rects = getRangeRects(range: selectedRange, ctframe: ctFrame)
        setNeedsDisplay()
    case .ended:
        print("longPress-Ended")
    case .cancelled:
        print("longPress-Cancelled")
    default:
        break
    }
    }

3.其中根据点击位置获取range和根据range获取rect的两个方法如下

 //MARK: - 获取点击位置的两个字符的range
private func getTouchLocationRange(point: CGPoint) -> NSRange {
    var resultRange = NSRange(location: 0, length: 0)
    guard let ctFrame = ctFrame else { return resultRange }
    
    var lines = CTFrameGetLines(ctFrame) as Array
    var origins = [CGPoint](repeating: CGPoint.zero, count: lines.count)
    CTFrameGetLineOrigins(ctFrame, CFRange(location: 0, length: 0), &origins)
    
    for i in 0..<lines.count {
        let line = lines[i] as! CTLine
        let origin = origins[I]
        
        var ascent: CGFloat = 0
        var descent: CGFloat = 0
        
        CTLineGetTypographicBounds(line, &ascent, &descent, nil)
        
        let lineRect = CGRect(x: origin.x, y: self.frame.height - origin.y - (ascent + descent), width: CTLineGetOffsetForStringIndex(line, 100000, nil), height: ascent + descent)
        
        if lineRect.contains(point) {
            
            let lineRange = CTLineGetStringRange(line)
            for j in 0..<lineRange.length {
                
                let index = lineRange.location + j
                
                var offsetX = CTLineGetOffsetForStringIndex(line, index, nil)
                var offsetX2 = CTLineGetOffsetForStringIndex(line, index + 1, nil)
                
                offsetX += origin.x
                offsetX2 += origin.x
                
                let runs = CTLineGetGlyphRuns(line) as Array
                
                for k in 0..<runs.count {
                    let run = runs[k] as! CTRun
                    let runRange = CTRunGetStringRange(run)
                
                    if runRange.location <= index && index <= (runRange.location + runRange.length - 1) {
                        
                        // 说明在当前的run中
                        var ascent: CGFloat = 0
                        var descent: CGFloat = 0
                        
                        CTRunGetTypographicBounds(run, CFRange(location: 0, length: 0), &ascent, &descent, nil)
                        
                        let frame = CGRect(x: offsetX, y: self.frame.height - origin.y - (ascent + descent), width: (offsetX2 - offsetX) * 2, height: ascent + descent)
                        
                        if frame.contains(point) {
                            // 每次获取两个字符的长度
                            resultRange = NSRange(location: index, length: 2)
                        }

                    }
                    
                }
        }
        
    }
    }
    
    return resultRange
}


//MARK: - 获取range所占用的rects
private func getRangeRects(range: NSRange, ctframe: CTFrame?) -> [CGRect] {
    var rects = [CGRect]()
    guard let ctframe = ctframe else { return rects }
    guard range.location != NSNotFound else { return rects }
    
    var lines = CTFrameGetLines(ctframe) as Array
    var origins = [CGPoint](repeating: CGPoint.zero, count: lines.count)
    CTFrameGetLineOrigins(ctframe, CFRange(location: 0, length: 0), &origins)
    
    for i in 0..<lines.count {
        let line = lines[i] as! CTLine
        let origin = origins[I]
        let lineCFRange = CTLineGetStringRange(line)
        
        if lineCFRange.location != NSNotFound {
            let lineRange = NSRange(location: lineCFRange.location, length: lineCFRange.length)
            
            if lineRange.location + lineRange.length > range.location && lineRange.location < (range.location + range.length) {
                
                var ascent: CGFloat = 0
                var descent: CGFloat = 0
                var startX: CGFloat = 0
                
                var contentRange = NSRange(location: range.location, length: 0)
                let end = min(lineRange.location + lineRange.length, range.location + range.length)
                contentRange.length = end - contentRange.location
                
                CTLineGetTypographicBounds(line, &ascent, &descent, nil)
                
                let y = origin.y - descent
                
                startX = CTLineGetOffsetForStringIndex(line, contentRange.location, nil)
                
                let endX = CTLineGetOffsetForStringIndex(line, contentRange.location + contentRange.length, nil)
                
                let rect = CGRect(x: origin.x + startX, y: y, width: endX - startX, height: ascent + descent)
                
                rects.append(rect)
                
            }
            
        }
        
    }

    return rects
}