Canvas实现圆形进度条并显示数字百分比

来源：动视网责编：小采时间：2020-11-27 15:10:21

Canvas实现圆形进度条并显示数字百分比

Canvas实现圆形进度条并显示数字百分比:实现效果1.首先创建html代码<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>2.创建canvas环境var canvas = doc

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导读Canvas实现圆形进度条并显示数字百分比:实现效果1.首先创建html代码<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>2.创建canvas环境var canvas = doc

实现效果

1.首先创建html代码

<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>

2.创建canvas环境

var canvas = document.getElementById('canvas'), //获取canvas元素
 context = canvas.getContext('2d'), //获取画图环境，指明为2d
 centerX = canvas.width/2, //Canvas中心点x轴坐标
 centerY = canvas.height/2, //Canvas中心点y轴坐标
 rad = Math.PI*2/100, //将360度分成100份，那么每一份就是rad度
 speed = 0.1; //加载的快慢就靠它了

3.绘制5像素宽的运动外圈

//绘制5像素宽的运动外圈
 function blueCircle(n){
 context.save();
 context.strokeStyle = "#fff"; //设置描边样式
 context.lineWidth = 5; //设置线宽
 context.beginPath(); //路径开始
 context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/2 +n*rad, false); //用于绘制圆弧context.arc(x坐标，y坐标，半径，起始角度，终止角度，顺时针/逆时针)
 context.stroke(); //绘制
 context.closePath(); //路径结束 context.restore();
 }

4.绘制白色外圈

//绘制白色外圈
 function whiteCircle(){
 context.save();
 context.beginPath();
 context.lineWidth = 2; //设置线宽
 context.strokeStyle = "red";
 context.arc(centerX, centerY, 100 , 0, Math.PI*2, false);
 context.stroke();
 context.closePath();
 context.restore();
 }

5.百分比文字绘制

function text(n){
 context.save(); //save和restore可以保证样式属性只运用于该段canvas元素
 context.strokeStyle = "#fff"; //设置描边样式
 context.font = "40px Arial"; //设置字体大小和字体
 //绘制字体，并且指定位置
 context.strokeText(n.toFixed(0)+"%", centerX-25, centerY+10);
 context.stroke(); //执行绘制 context.restore();
 }

6.让它运动起来

//动画循环
 (function drawFrame(){ window.requestAnimationFrame(drawFrame);
 context.clearRect(0, 0, canvas.width, canvas.height);
 whiteCircle();
 text(speed);
 blueCircle(speed); if(speed > 100) speed = 0;
 speed += 0.1;
 }());

完整代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>HTML5 Canvas 圆形进度条并显示数字百分比</title>

<style>
*{margin:0;padding:0;}
body{text-align:center;background-color:#000;}
</style>

</head>
<body>

<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>
<script>
 window.onload = function(){
 var canvas = document.getElementById('canvas'), //获取canvas元素
 context = canvas.getContext('2d'), //获取画图环境，指明为2d
 centerX = canvas.width/2, //Canvas中心点x轴坐标
 centerY = canvas.height/2, //Canvas中心点y轴坐标
 rad = Math.PI*2/100, //将360度分成100份，那么每一份就是rad度
 speed = 0.1; //加载的快慢就靠它了 
 
 //绘制5像素宽的运动外圈
 function blueCircle(n){
 context.save();
 context.strokeStyle = "#fff"; //设置描边样式
 context.lineWidth = 5; //设置线宽
 context.beginPath(); //路径开始
 context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/2 +n*rad, false); //用于绘制圆弧context.arc(x坐标，y坐标，半径，起始角度，终止角度，顺时针/逆时针)
 context.stroke(); //绘制
 context.closePath(); //路径结束
 context.restore();
 }
 //绘制白色外圈
 function whiteCircle(){
 context.save();
 context.beginPath();
 context.lineWidth = 2; //设置线宽
 context.strokeStyle = "red";
 context.arc(centerX, centerY, 100 , 0, Math.PI*2, false);
 context.stroke();
 context.closePath();
 context.restore();
 } 
 //百分比文字绘制
 function text(n){
 context.save(); //save和restore可以保证样式属性只运用于该段canvas元素
 context.strokeStyle = "#fff"; //设置描边样式
 context.font = "40px Arial"; //设置字体大小和字体
 //绘制字体，并且指定位置
 context.strokeText(n.toFixed(0)+"%", centerX-25, centerY+10);
 context.stroke(); //执行绘制
 context.restore();
 } 
 //动画循环
 (function drawFrame(){
 window.requestAnimationFrame(drawFrame);
 context.clearRect(0, 0, canvas.width, canvas.height);
 whiteCircle();
 text(speed);
 blueCircle(speed);
 if(speed > 100) speed = 0;
 speed += 0.1;
 }());
 }
</script>

</body>
</html>