Detailed explanation of the example method of realizing arc and ring progress bars on canvas-H5 Tutorial-php.cn

Detailed explanation of the example method of realizing arc and ring progress bars on canvas

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Release： 2017-05-27 15:26:02

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The following summarizes how to achieve the circular progress bar effect in my project. I hope it will be helpful to everyone:

This method draws a circle through canvas To realize the dynamic ring progress bar using the shape method, enter the code directly. If you have any questions, please see the comments:

The HTML code is as follows. Just create a canvas on the page:

<canvas id="canvas" width="300" height="300">
    <p>抱歉，您的浏览器不支持canvas</p>
 </canvas>

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JS is divided into two parts,
The first part implements the overall function, and the second part calls:
The first part:
The functional principle of the first part is roughly to draw two circles, one is the background color Circle, the second one is a dynamically loaded arc, the progress is loaded through timer; the color is added with gradient color;

 function toCanvas(id ,progress){                canvas进度条
                var canvas = document.getElementById(id),
                ctx = canvas.getContext("2d"),
                percent = progress,  最终百分比                circleX = canvas.width / 2,  中心x坐标                circleY = canvas.height / 2,  中心y坐标                radius = 100, 圆环半径                lineWidth = 5,  圆形线条的宽度                fontSize = 20; 字体大小
                 两端圆点
                function smallcircle1(cx, cy, r) {
                    ctx.beginPath();                    //ctx.moveTo(cx + r, cy);                    ctx.lineWidth = 1;
                    ctx.fillStyle = &#39;#06a8f3&#39;;
                    ctx.arc(cx, cy, r,0,Math.PI*2);
                    ctx.fill();
                }                 function smallcircle2(cx, cy, r) {
                     ctx.beginPath();                     //ctx.moveTo(cx + r, cy);                     ctx.lineWidth = 1;
                     ctx.fillStyle = &#39;#00f8bb&#39;;
                     ctx.arc(cx, cy, r,0,Math.PI*2);
                     ctx.fill();
                 }                 画圆
                 function circle(cx, cy, r) {
                     ctx.beginPath();                     //ctx.moveTo(cx + r, cy);                     ctx.lineWidth = lineWidth;
                     ctx.strokeStyle = &#39;#eee&#39;;
                     ctx.arc(cx, cy, r, Math.PI*2/3, Math.PI * 1/3);
                     ctx.stroke();
                 }                 画弧线
                 function sector(cx, cy, r, startAngle, endAngle, anti) {
                     ctx.beginPath();                     //ctx.moveTo(cx, cy + r); // 从圆形底部开始画                     ctx.lineWidth = lineWidth;                     // 渐变色 - 可自定义
                     var linGrad = ctx.createLinearGradient(
                         circleX-radius-lineWidth, circleY, circleX+radius+lineWidth, circleY
                     );
                     linGrad.addColorStop(0.0, &#39;#06a8f3&#39;);                     //linGrad.addColorStop(0.5, &#39;#9bc4eb&#39;);                     linGrad.addColorStop(1.0, &#39;#00f8bb&#39;);
                     ctx.strokeStyle = linGrad;                      圆弧两端的样式                     ctx.lineCap = &#39;round&#39;;                     圆弧                     ctx.arc(
                         cx, cy, r,
                         (Math.PI*2/3),                         (Math.PI*2/3) + endAngle/100 * (Math.PI*5/3),
                         false
                     );
                     ctx.stroke();
                 }                  刷新
                 function loading() {                     if (process >= percent) {
                         clearInterval(circleLoading);
                     }                      清除canvas内容                     ctx.clearRect(0, 0, circleX * 2, circleY * 2);                    中间的字                     ctx.font = fontSize + &#39;px April&#39;;
                     ctx.textAlign = &#39;center&#39;;
                     ctx.textBaseline = &#39;middle&#39;;
                     ctx.fillStyle = &#39;#999&#39;;
                     ctx.fillText(parseFloat(process).toFixed(0) + &#39;%&#39;, circleX, circleY);    
                  
                     圆形                     circle(circleX, circleY, radius);                     
                      圆弧                     sector(circleX, circleY, radius, Math.PI*2/3, process);
                     两端圆点                     smallcircle1(150+Math.cos(2*Math.PI/360*120)*100, 150+Math.sin(2*Math.PI/360*120)*100, 5);
                     smallcircle2(150+Math.cos(2*Math.PI/360*(120+process*3))*100, 150+Math.sin(2*Math.PI/360*(120+process*3))*100, 5);                     控制结束时动画的速度
                     if (process / percent > 0.90) {
                         process += 0.30;
                     } else if (process / percent > 0.80) {
                         process += 0.55;
                     } else if (process / percent > 0.70) {
                         process += 0.75;
                     } else {
                         process += 1.0;
                     }
                 }                 var process = 0.0;  进度
                 var circleLoading = window.setInterval(function () {
                     loading();
                 }, 20);
                     
            }
第二部分，调用封装好的代码：
            toCanvas(&#39;canvas&#39;,50);

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