如何通过HTMl5 Canvas实现圆形进度条并显示数字百分比效果?

如何通过HTMl5 Canvas实现圆形进度条并显示数字百分比效果?

本文介绍了HTML5 Canvas 实现圆形进度条并显示数字百分比效果示例,具体如下:

实现效果

如何通过HTMl5 Canvas实现圆形进度条并显示数字百分比效果?

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 lang="en">
<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>

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持路饭。