WXML代码
<view class="wrap">
  <view class="circleBox ">
    <canvas class="circle c1" canvas-id="canvasCircle">
    </canvas>
    <canvas class="circle c2" canvas-id="canvasArcCir">
    </canvas>
    <view class="drawBtn" bindtap="drawCircle">开始动态绘制</view>
  </view>
</view>

WXSS代码
Page {
  width: 100%;
  height: 100%;
  background-color: #fff;
}

.circleBox {
  text-align: center;
  margin-top: 100rpx;
}

.circle {
  position: absolute;
  left: 0;
  right: 0;
  margin: auto;
}

.c1 {
  z-index: -99;
  width:300rpx;
  height:300rpx;
}
.c2 {
  width:300rpx;
  height:300rpx;
}

.drawBtn {
  width: 70rpx;
  position: absolute;
  top: 60rpx;
  right: 0;
  left: 0;
  margin: 0 auto;
  border: 1px #000000 solid;
  border-radius: 10rpx;
}

js
//获取应用实例
var app = getApp()
var interval;
var varName;
var ctx = wx.createCanvasContext('canvasArcCir');

Page({
  data: {
  },
  onReady: function () {
    //创建并返回绘图上下文context对象。
    var cc = wx.createCanvasContext('canvasCircle');
    cc.setLineWidth(6);
    cc.setStrokeStyle('#eaeaea');
    cc.setLineCap('round');
    cc.beginPath();
    cc.arc(100, 100, 96, 0, 2 * Math.PI, false);
    cc.stroke();
    cc.draw();
  },
  onLoad: function (options) {

  }
  drawCircle: function () {
    clearInterval(varName);
    function drawArc(s, e) {
      ctx.setFillStyle('white');
      ctx.clearRect(0, 0, 200, 200);
      ctx.draw();
      var x = 100, y = 100, radius = 96;
      ctx.setLineWidth(5);
      ctx.setStrokeStyle('#d81e06');
      ctx.setLineCap('round');
      ctx.beginPath();
      ctx.arc(x, y, radius, s, e, false);
      ctx.stroke()
      ctx.draw()
    }
    var step = 1, startAngle = 1.5 * Math.PI, endAngle = 0;
    var animation_interval = 1000, n = 60;
    var animation = function () {
      if (step <= n) {
        endAngle = step * 2 * Math.PI / n + 1.5 * Math.PI;
        drawArc(startAngle, endAngle);
        step++;
      } else {
        clearInterval(varName);
      }
    };
    varName = setInterval(animation, animation_interval);
  },
})