QuartzCore - CATextLayer

CATextLayer 垂直居中显示，自定义 CATextLayer ，重写 draw(in ctx:) 方法

class CustomTextLayer: CATextLayer {

    public override init() {
      super.init()
    }

    public override init(layer: Any) {
      super.init(layer: layer)
    }

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

    public override func draw(in ctx: CGContext) {

      let mFontSize = (string as? NSAttributedString)?.size().height ?? fontSize
      let yDiff = (bounds.size.height - mFontSize) * 0.5 + mFontSize * 0.1

      ctx.saveGState()
      ctx.translateBy(x: 0.0, y: yDiff)
      super.draw(in: ctx)
      ctx.restoreGState()

    }
    
}