react canvas圆环动态百分比

import React from 'react';

import Tools from '../../tools/index'

export default class PercentageRing extends React.Component {

constructor(props){

super(props);

}

componentDidMount() {

let canvas = this.refs.ring;

let width = canvas.offsetWidth;

let height = canvas.offsetHeight;

let context = canvas.getContext('2d');

// this.rings();

let i = 1;

let percent = 30;

this.timerId = setInterval(()=>{

i >= percent && clearInterval(this.timerId);

context.clearRect(0,0,width+10,height);

this.draw(i++);

},50)

}

draw(i){

let canvas = this.refs.ring;

let width = canvas.offsetWidth;

let height = canvas.offsetHeight;

let context = canvas.getContext('2d');

let rad = Math.PI*2/100;

canvas.width = width;

canvas.height = height;

// 绘制一个圆

context.beginPath(); // 开始创建路径

context.arc(width/2,height/2,height/2-10,0,2*Math.PI,false);

context.lineWidth = 10;

context.strokeStyle="#12365a"; // 轮廓颜色

context.lineCap = "round"; // 绘制圆帽

context.stroke(); // 通过线条来绘制轮廓

context.closePath(); // 关闭路径

// this.draw();

context.beginPath();

context.font = `${72/320}rem PingFang SC`;

context.textAlign = 'right';

context.textBaseline = 'bottom';

context.fillStyle="#00a8ff";

context.fillText('%',width/2+110,height/2+25);

context.stroke();

context.closePath();

// 绘制半圆

context.beginPath();

context.arc(width/2,height/2,height/2-10,-Math.PI/2,-Math.PI/2+i*rad,false);

context.lineWidth = 10;

// 创建渐变颜色

let linearGrad = context.createLinearGradient(0,0,width,height);

linearGrad.addColorStop(0.0, '#02a7ff');

linearGrad.addColorStop(0.25, '#1da1fb');

linearGrad.addColorStop(0.5, '#5893f4');

linearGrad.addColorStop(0.75, '#9484ec');

context.strokeStyle = linearGrad;

context.stroke();

context.closePath();

// 绘制文本信息

context.beginPath();

context.font = `${236/302}rem PingFang SC`;

context.textAlign = 'center';

context.textBaseline = 'middle';

context.fillStyle = "#00a8ff";

context.fillText(i.toFixed(0),width/2,height/2); // 绘制文本最大宽度

context.stroke();

context.closePath();

}

componentWillUnmount(){

　　this.timerId && clearInterval(this.timerId);

}

render() {

return (

<div className="perent-ring-box">

<canvas className="perent-canvas" ref='ring'>

<p>请使用最新的谷歌、火狐、IE浏览器</p>

<p>您的浏览器不支持</p>

</canvas>

</div>

)

 

}

}