private func zhiXian(){

         // 1、“获取”图形上下文对象

         let cxtRef = UIGraphicsGetCurrentContext()!

         // 2、添加直线路径

         cxtRef.move(to: CGPoint(x: , y: ))

         cxtRef.addLine(to: CGPoint(x: , y: ))

         // 3、描边渲染

         cxtRef.strokePath()

     }

 private func sanJiaoXing(){

         // 1、“获取”图形上下文对象

         let cxtRef = UIGraphicsGetCurrentContext()!

         // 2、添加三角形路径

         let point1 = CGPoint(x: , y: )

         let point2 = CGPoint(x: , y: )

         let point3 = CGPoint(x: , y: )

         // cxtRef.addLines(between: [point1,point2,point3])

         cxtRef.move(to: point1)

         cxtRef.addLine(to: point2)

         cxtRef.addLine(to: point3)

         // 3、关闭路径 -> 将路径的终点向起点连线

         cxtRef.closePath()

         // 4、渲染

         // stroke - 描边，只画线条

         // cxtRef.strokePath()

         // fill - 填充，负责里面的内容，不管边线

         cxtRef.fillPath()

     }

     private func juXing(rect:CGRect){

         // 1、获取图形上下文对象

         let cxtRef = UIGraphicsGetCurrentContext()!

         // 2、添加矩形路径

         cxtRef.addRect(CGRect(x: , y: , width: , height: ))

         // 3、描边渲染

         cxtRef.strokePath()

     }

     private func tuoYuanXing(){

         // 1、获取图形上下文对象

         let cxtRef = UIGraphicsGetCurrentContext()!

         // 2、添加椭圆形路径 - 内切圆

         cxtRef.addEllipse(in: CGRect(x: , y: , width: , height: ))

         // 3、描边渲染

         cxtRef.strokePath()

     }

     private func huXing(){

         // 1、获取图形上下文对象

         let cxtRef = UIGraphicsGetCurrentContext()!

         // 2、添加弧形路径

         // clockwise: true - 逆时针；false - 顺时针

         cxtRef.addArc(center: CGPoint(x:,y:), radius: , startAngle: , endAngle: CGFloat(M_PI_4), clockwise: false)

         // 3、描边渲染

         cxtRef.strokePath()

     }