在 CAShapelayer 上绘制文本

Question

我正在使用 coregraphics 绘制一条线，并且我想使用 core graphics 绘制一些文本。 我的代码如下；

导入 UIKit

class ArrowLineLayer: CAShapeLayer {

    var startingGlyph : CGRect!

    override init() {
        super.init()
        let fontName = "HelveticaNeue-Bold"
        let font = UIFont(name:fontName , size: 15)
        let measurementString = "28 cm" as NSString
        measurementString.draw(at: CGPoint(x:150,y:100), withAttributes: [NSAttributedStringKey.font: font!])

    }

    func drawArrow(frame:CGRect)
    {
        self.frame = frame
        self.lineWidth = 3
        self.strokeColor = UIColor.red.cgColor
        self.lineCap = "round"

        let path = CGMutablePath()
        path.move(to: CGPoint(x:100 , y:100))
        path.addLine(to: CGPoint(x:200 , y:100))
        let radius: CGFloat = 5.0
        let rect = CGRect(x:100 - radius, y: 100 - radius , width: 2 * radius, height: 2 * radius)
        startingGlyph = rect
        path.addPath(UIBezierPath(ovalIn: rect).cgPath)
        self.path = path
    }


    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }


}

然后我初始化这个层并将其添加到主视图层。我可以看到该行，但看不到文本。我不想使用 CATextlayer，因为我想将整个逻辑保存在一个地方。谁能指出我缺少什么？

问候， 尼娜

Answer 1

您可以使用NSAttributedString 创建UIBezierPath，然后将此路径附加到您现有的路径中。

extension UIBezierPath {

    convenience init(text: NSAttributedString) {
        let textPath = CGMutablePath()
        let line = CTLineCreateWithAttributedString(text)

        let runs = CTLineGetGlyphRuns(line) as! [CTRun]

        for run in runs
        {
            let attributes: NSDictionary = CTRunGetAttributes(run)
            let font = attributes[kCTFontAttributeName as String] as! CTFont

            let count = CTRunGetGlyphCount(run)

            for index in 0 ..< count
            {
                let range = CFRangeMake(index, 1)

                var glyph = CGGlyph()
                CTRunGetGlyphs(run, range, &glyph)

                var position = CGPoint()
                CTRunGetPositions(run, range, &position)

                let letterPath = CTFontCreatePathForGlyph(font, glyph, nil)
                let transform = CGAffineTransform(translationX: position.x, y: position.y)

                textPath.addPath(letterPath!, transform: transform)
            }
        }

        self.init(cgPath: textPath)
    }
}