JavaScript canvas实现围绕旋转动画

function Circle(obj) { 
 this._init(obj); 
} 
Circle.prototype = { 
 _init: function (obj) { 
  this.x = obj.x, //圆心x轴的坐标 
  this.y = obj.y, //圆心y轴的坐标 
  this.outR = obj.outR, //外圆的半径 
  this.inR = obj.inR, //内圆的半径 
  this.color = obj.fill, //填充颜色 
  this.text = obj.text, //内圆的文字 
  this.outOpacity = obj.outOpacity, //外圆的透明度 
  this.inOpacity = obj.inOpacity  //内圆的透明度 
 }, 
 drawCircle: function (group) { 
  //创建一个组 
  var groupCir = new Konva.Group({ 
   x: this.x, 
   y: this.y 
  }); 
  //外圆 
  var outCir = new Konva.Circle({ 
   x: 0, 
   y: 0, 
   radius: this.outR, 
   fill: this.color, 
   opacity: this.outOpacity 
  }); 
  groupCir.add(outCir); 
  //内圆 
  var inCir = new Konva.Circle({ 
   x: 0, 
   y: 0, 
   radius: this.inR, 
   fill: this.color, 
   opacity: this.inOpacity 
  }); 
  groupCir.add(inCir); 
  //添加文字 
  var text = new Konva.Text({ 
   x: -this.inR, 
   y: -10, 
   text: this.text, 
   fill: "white", 
   fontSize: 20, 
   width: 2 * this.inR, 
   align: "center" 
  }); 
  groupCir.add(text); 
 
  group.add(groupCir); 
 } 
}