实现效果

1.首先创建html代码

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

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

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"; 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

HTML5 Canvas 圆形进度条并显示数字百分比 * body window.onload = function(){ blueCircle(n){ context.save(); context.strokeStyle context.restore(); } whiteCircle(){ context.save(); context.beginPath(); context.lineWidth ; context.arc(centerX, centerY, ); context.stroke(); context.closePath(); context.restore(); } text(n){ context.save(); ); context.stroke(); //执行绘制 context.restore(); } drawFrame(){ window.requestAnimationFrame(drawFrame); context.clearRect(, canvas.width, canvas.height); whiteCircle(); text(speed); blueCircle(speed); ; speed += 0.1; }()); }