本文实例为大家分享了JavaScript canvas绘制动态圆环进度条的具体代码，供大家参考，具体内容如下
由于使用的是vue开发，所以就展示一下绘制函数好了，上图是效果图
drawMain(drawing_elem, percent, forecolor, bgcolor) {
var context = drawing_elem.getContext("2d");
var center_x = drawing_elem.width / 2;
var center_y = drawing_elem.height / 2;
var rad = Math.PI*2/100;
var speed = 0;
// 绘制背景圆圈
function backgroundCircle(){
context.save();
context.beginPath();
context.lineWidth = 8; //设置线宽
var radius = center_x - context.lineWidth;
context.lineCap = "round";
context.strokeStyle = bgcolor;
context.arc(center_x, center_y, radius, 0, Math.PI*2, false);
context.stroke();
context.closePath();
context.restore();
}
//绘制运动圆环
function foregroundCircle(n){
context.save();
context.strokeStyle = forecolor;
context.lineWidth = 8;
context.lineCap = "round";
var radius = center_x - context.lineWidth;
context.beginPath();
context.arc(center_x, center_y, radius , -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();
context.closePath();
context.restore();
}
//绘制文字
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.fillStyle = forecolor;
var font_size = 40;
context.font = font_size + "px Helvetica";
var text_width = context.measureText(n.toFixed(0)+"%").width;
context.fillText(n.toFixed(0)+"%", center_x-text_width/2, center_y + font_size/2);
context.restore();
}
//执行动画
(function drawFrame(){
window.requestAnimationFrame(drawFrame);
context.clearRect(0, 0, drawing_elem.width, drawing_elem.height);
backgroundCircle();
text(speed);
foregroundCircle(speed);
if(speed >= percent) return;
speed += 1;
}());
},调用的话
var time_canvas = document.getElementById("time-graph-canvas");
this.drawMain(time_canvas, 70, "#85d824", "#eef7e4");
var weather_canvas = document.getElementById("weather-graph-canvas");
this.drawMain(weather_canvas, 90, "#2ba0fb", "#e5f1fa");html文件
<div class="time-graph">
<canvas id="time-graph-canvas" width="160" height="160"></canvas>
</div>css文件
.time-graph {
padding-top: 20px;
display:flex;
display:-webkit-flex;
justify-content: center;
align-items: center;
}
#time-graph-canvas {
width: 80px;
height: 80px;
}有些绘制细节需要注意，为了保证绘制的清晰度，canvas的大小需要设置为canvas父元素大小的2倍。
其他的代码都有详细的注释，自己拷一下，运行一下就知道
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编程网。
