canvas画圆动态显示百分比

最新推荐文章于 2023-09-02 18:39:36 发布

Garon_InE

最新推荐文章于 2023-09-02 18:39:36 发布

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CC 4.0 BY-SA版权

分类专栏： javascript 文章标签： canvas 画圆百分比动态

本文链接：https://blog.youkuaiyun.com/qq_22253823/article/details/54317741

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这篇博客介绍了如何利用HTML5的canvas元素，结合JavaScript和CSS，实现一个动态展示百分比的圆形进度条。通过circle.js和circle.css文件的详细讲解，阐述了从创建canvas元素到绘制圆环，再到实时更新百分比的过程。

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circle.js

var circleTimer;
var circleFlag = false;
var circle = {
    run:function(opts)
    {
        if(!opts.id) throw new Error("must be canvas id.");
        //暂不能用jq的$获取canvas
        var canvas = document.getElementById(opts.id), ctx;
        if(canvas && (ctx = canvas.getContext("2d")))
        {
            canvas.width = canvas.height = "300";
            var noop = function(){};
            var before = opts.onBefore || noop;
            var ringDo = opts.onRingDo || noop;
            var after = opts.onAfter || noop;
            before(ctx);
            var step = opts.step || 1;
            var delay = opts.delay || 100;
            var myRageNow = 0;
            var myStepNow = 0;
            var myRage = 360 * (opts.percent || 0);
            var sRage = -Math.PI * 0.5;
            var doDraw = function()
            {
                circleFlag = true;
                myRageNow += step;
                myStepNow += step;
                if(myRageNow <= myRage)
                {
                    if(myStepNow == 361)
                    {
                        myStepNow = 1;
                        ringDo(ctx);
                    }
                    ctx.fillStyle = opts.color || '#f76220';
                    ctx.beginPath();
                    ctx.moveTo(150, 150);   
                    ctx.arc(150, 150, 150, sRage, Math.PI * 2 * (myStepNow/360) + sRage);
                    ctx.fill();
                    circleTimer = setTimeout(doDraw, delay);
                } 
                else 
                {
                    circleFlag = false;
                    after(ctx);
                }
            };

            doDraw();
        }
    }
};

//将百分比转换成小数
function percentTofloat(km)
{
    if(km.substring(km.length-1,km.length)=="%")
    {
        km = km.substring(0,km.length-1);
        km = km/100;
    }
    return km;
}

//绑定控件，启动转动
function circleBind(my_id,my_percent)
{
    circle.run(
    {
        id:my_id,
        percent: percentTofloat(my_percent),
        onBefore:function(ctx){
            ctx.fillStyle = '#e8e8e8';
            ctx.beginPath();
            ctx.moveTo(150, 150);   
            ctx.arc(150, 150, 150, 0, Math.PI * 2);
            ctx.fill();
        },
        onRingDo:function(ctx){
            ctx.fillStyle = '#e8e8e8';
            ctx.beginPath();
            ctx.moveTo(150, 150);   
            ctx.arc(150, 150, 150, 0, Math.PI * 2);
            ctx.fill();
        }
    });
}

//停止转动
function circleStop()
{
    clearTimeout(circleTimer);
}

//获取控件状态
function circleStatus()
{
    return circleFlag;
}

circle.css

@charset "utf-8";
/* CSS Document */
.round-wrap{
    display:block;
    position:relative;
    width:100px;
    height:100px;
    overflow:hidden;
    border-radius:65px;
    -webkit-border-radius:65px;
}
.round-sector{
    position:absolute;
    width:100px;
    height:100px;
}
.round-bg { 
    position:absolute;
    width:100px;
    height:100px;
    background-color:#f76220;
    border-radius:65px;
    -webkit-border-radius:65px;
}
.round-circle{
    position:absolute;
    background-color:#FFF;
    width:94px;
    height:94px;
    left:2.5px;
    top:2.5px;
    z-index:10;
    border-radius:60px;
    -webkit-border-radius:60px;
}
.round-circle p{
    font-size:14px;
    line-height:94px;
    margin:0;
    text-align:center;
    width:100%;
    font-weight:bold;
}

html

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>canvas画圆动态显示百分比</title>
<link type="text/css" rel="stylesheet" href="css/circle.css"/>
<script type="text/javascript" src="js/jquery.min.js"></script>
</head>
<body>
<div class="round-wrap">
    <div class="round-bg"></div>
    <canvas id="crl0" class="round-sector"></canvas>
    <div class="round-circle"><p>2</p></div>
</div>
<div class="round-wrap">
    <div class="round-bg"></div>
    <canvas id="crl1" class="round-sector"></canvas>
    <div class="round-circle"><p>60%</p></div>
</div>
<div class="round-wrap">
    <div class="round-bg"></div>
    <canvas id="crl2" class="round-sector"></canvas>
    <div class="round-circle"><p>0.89</p></div>
</div>
<script type="text/javascript" src="js/circle.js"></script>
<script>
    $(document).ready(function() 
    {
        circleBind("crl0","2");
        circleBind("crl1","60%");
        circleBind("crl2","0.89");
    });
</script>
</body>
</html>