微信小程序动画之圆形进度条

上图：

js：

//获取应用实例

var app = getApp()

var interval;

var varName;

var ctx = wx.createCanvasContext('canvasArcCir');

Page({

  data: {

  },

  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(7);

      ctx.setStrokeStyle('#BFEFFF');

      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 * 8 * Math.PI / n + 1.5 * Math.PI;

        drawArc(startAngle, endAngle);

        step++;

      } else {

        clearInterval(varName);

      }

    };

    varName = setInterval(animation, animation_interval);

  },

  onReady: function () {

    //创建并返回绘图上下文context对象。

    var cxt_arc = wx.createCanvasContext('canvasCircle');

    cxt_arc.setLineWidth(8);

    cxt_arc.setStrokeStyle('#EDEDED');

    cxt_arc.setLineCap('round');

    cxt_arc.beginPath();

    cxt_arc.arc(100, 100, 96, 0, 2 * Math.PI, false);

    cxt_arc.stroke();

    cxt_arc.draw();

  },

  onLoad: function (options) {

  }

})

wxml：

<view class="wrap">

  <view class="circle-box">

    <canvas class="circle" style="width:200px; height:200px;" canvas-id="canvasArcCir">

    </canvas>

    <canvas class="circle" style="z-index: -5; width:200px; height:200px;" canvas-id="canvasCircle">

    </canvas>

    <view class="draw_btn" bindtap="drawCircle">点击开始</view>

  </view>

</view>

wxss：

page {

  width: 100%;

  height: 100%;

  background-color: #fff;

}

.circle-box {

  text-align: center;

  margin-top: 10vw;

}

.circle {

  position: absolute;

  left:;

  right:;

  margin: auto;

}

.draw_btn {

  width: 28vw;

  position: absolute;

  top: 31vw;

  right:;

  left:;

  margin: auto;

  border: 1px #0D0D0D solid;

   background-color: #BFEFFF;

  border-radius: 5vw;

}