Detailed explanation of real-time circular progress bar for mini program development

Recently, in order to make a recording button, I studied the implementation of the real-time circular progress bar of the mini program

Without further ado, here is a rendering first!

Initial state

##Click the middle button to start drawing

Drawing process

End of drawing

Implementation ideas

Establish two

canvas tag, first draw the bottom layer of light gray circle background, and then draw the upper layer of red progress bar.

WXML code

<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">开始动态绘制</view>
  </view>
</view>

WXSSCode

Special note: It is best to use the underlying canvas

z-index:-5 ; Placed at the bottom layer

page {
  width: 100%;
  height: 100%;
  background-color: #fff;
}

.circle-box {
  text-align: center;
  margin-top: 10vw;
}

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

.draw_btn {
  width: 35vw;
  position: absolute;
  top: 33vw;
  right: 0;
  left: 0;
  margin: auto;
  border: 1px #000 solid;
  border-radius: 5vw;
}

JSCode

//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(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);
  },
  onReady: function () {
    //创建并返回绘图上下文context对象。
    var cxt_arc = wx.createCanvasContext(&#39;canvasCircle&#39;);
    cxt_arc.setLineWidth(6);
    cxt_arc.setStrokeStyle(&#39;#eaeaea&#39;);
    cxt_arc.setLineCap(&#39;round&#39;);
    cxt_arc.beginPath();
    cxt_arc.arc(100, 100, 96, 0, 2 * Math.PI, false);
    cxt_arc.stroke();
    cxt_arc.draw();
  },
  onLoad: function (options) {

  }
})

Points to note

1. For mini program canvas drawing, please view the WeChat mini program official documentation Draw

2. The path to start drawing can be based on the variable startAngle

in the JS code to choose where to start drawing

Finally there is You can leave a message if you have any questions, and let’s discuss and make progress together~~

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