详解利用canvas实现环形进度条的方法canvas实现圆形进度条动画的示例代码HTML5 Canvas 实现圆形进度条并显示数字百分比效果示例HTML5 Canvas玩转酷炫大波浪进度图效果实例（附demo）

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 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 //绘制蓝色外圈 function blueCircle(n) { context.save(); context.beginPath(); context.strokeStyle = "#49f"; context.lineWidth = 12; context.arc(centerX, centerY, 100, -Math.PI / 2, -Math.PI / 2 + n * rad, false); context.stroke(); context.restore(); } //绘制白色外圈 function whiteCircle() { context.save(); context.beginPath(); context.strokeStyle = "#A5DEF1"; context.lineWidth = 12; 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(); context.fillStyle = "#F47C7C"; context.font = "40px Arial"; context.textAlign = "center"; context.textBaseline = "middle"; context.fillText(n.toFixed(0) + "%", centerX, centerY); context.restore(); } //动画循环 (function drawFrame() { window.requestAnimationFrame(drawFrame, canvas); context.clearRect(0, 0, canvas.width, canvas.height); whiteCircle(); text(speed); blueCircle(speed); if (speed > 100) speed = 0; speed += 0.1; }()); window.requestAnimationFrame(drawFrame, canvas);