Swift - 描边文字效果

项目需求，文字要有描边效果，在这里记录下来。 核心是使用NSAttributedString进行绘制。 建议将此方法写在扩展中。另外还看到一些博主写的描边效果，其方式是继承UILabel，然后重载drawTextInRect方法，我改成了Swift，在下面也一并附上，有兴趣的可以看看

overridefunc viewDidLoad() {
     super.viewDidLoad()
        
     let lab =UILabel(frame:view.bounds)
     lab.attributedText =drawOutlineAttributedString(string:"哎呦，不错哦", fontFloat:30, alignment: .center, textColor:UIColor.white, widthColor:UIColor.red)
      view.addSubview(lab)
    }

 func drawOutlineAttributedString(string:String? =nil, fontFloat:CGFloat,
                                  alignment: NSTextAlignment, textColor:UIColor,
                                  widthColor: UIColor) ->NSAttributedString {
        
      let paragraph =NSMutableParagraphStyle()
      paragraph.alignment = alignment
        
      let dic = [NSFontAttributeName:UIFont.systemFont(ofSize: fontFloat),
                 NSParagraphStyleAttributeName: paragraph,
                 NSForegroundColorAttributeName: textColor,
                 NSStrokeWidthAttributeName: (-1.5),
                 NSStrokeColorAttributeName: widthColor]as [String :Any]
        
      var attributedText:NSMutableAttributedString!
      if string !=nil{
          attributedText = NSMutableAttributedString.init(string: string!, attributes: dic)
      } else {
          attributedText = NSMutableAttributedString.init(string:"", attributes: dic)
      }
      return attributedText
 } 
           

重载drawTextInRect方法

overridefunc drawText(in rect: CGRect) {
        let shadowOffset =self.shadowOffset
        let textColor =self.textColor
        
        let c =UIGraphicsGetCurrentContext()
        c!.setLineWidth(1)
        c!.setLineJoin(.round)
        c!.setTextDrawingMode(.stroke)
        self.textColor =UIColor.white
        super.drawText(in: rect)
        
        c!.setTextDrawingMode(.fill)
        self.textColor = textColor
        self.shadowOffset =CGSize(width: CGFloat(0), height:CGFloat(0))
        super.drawText(in: rect)
        self.shadowOffset = shadowOffset
    }
           

效果如下：