Introduction to the method of implementing circular progress bar in WeChat applet-Mini Program Development-php.cn

Introduction to the method of implementing circular progress bar in WeChat applet

巴扎黑

Release： 2017-09-12 10:45:40

Original

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前言

最近工作中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，下面这篇文章就来给大家详细的介绍了实现的方法示例，废话不多说，先来看看效果图吧。

效果图如下

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

&lt;view class="wrap">
 &lt;view class="circle-box">
 &lt;canvas class="circle" style="width:200px; height:200px;" canvas-id="canvasArcCir">
 &lt;/canvas>
 &lt;canvas class="circle" style="z-index: -5; width:200px; height:200px;" canvas-id="canvasCircle">
 &lt;/canvas>
 &lt;view class="draw_btn" bindtap="drawCircle">开始动态绘制&lt;/view>
 &lt;/view>
&lt;/view>

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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;
}

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JS代码

//获取应用实例
var app = getApp()


var interval;
var varName;
var ctx = wx.createCanvasContext(&#39;canvasArcCir&#39;);


Page({
 data: {
 },
 drawCircle: function () {
 clearInterval(varName);
 function drawArc(s, e) {
 ctx.setFillStyle(&#39;white&#39;);
 ctx.clearRect(0, 0, 200, 200);
 ctx.draw();
 var x = 100, y = 100, radius = 96;
 ctx.setLineWidth(5);
 ctx.setStrokeStyle(&#39;#d81e06&#39;);
 ctx.setLineCap(&#39;round&#39;);
 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 &lt;= 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) {
 }
})

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注意的要点

1、关于小程序canvas绘制，请观看微信小程序官方文档绘制

2、开始绘制的路径可以根据 JS代码中的变量startAngle 来选择从哪里开始绘制

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