小程序开发之实时圆形进度条详解

互联网 18-5-18

最近为了做一个录制按钮，研究了下小程序的实时圆形进度条实现

废话不多说，先上一张效果图！

初始状态

点击中间按钮开始绘制

绘制过程

绘制结束

实现思路

建立两个canvas标签，先绘制底层的浅灰色圆圈背景，再绘制上层的红色进度条。

WXML代码

<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>

WXSS代码

特别注意：底层的canvas最好使用

z-index:-5；放置于底层

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;  }

JS代码

//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('canvasCircle');      cxt_arc.setLineWidth(6);      cxt_arc.setStrokeStyle('#eaeaea');      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) {      }  })