HTML5效果:Canvas 实现圆形进度条并显示数字百分比

时间:2019-01-30 13:46:11 来源:互联网 作者: 神秘的大神 字体:

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 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>