html5 canvas 倒计时
2016-06-09 本文已影响0人
Zoro_stack
<!DOCTYPE html>
<html>
<head>
<title>Canvas</title>
</head>
<body>
<canvas id="canvas" width="1000" height="1000"></canvas>
<script type="text/javascript">
var currentSeconds = 10;
var countDownSeconds = 10;
var interval_id = setInterval("drawDoubleCircle()", 1000);
function drawDoubleCircle() {
if (currentSeconds <= 0) {
clearInterval(interval_id);
}
var canvasElement = document.getElementById('canvas');
var context = canvasElement.getContext('2d');
progress = 360 * currentSeconds / countDownSeconds;
progress_pi = Math.PI * (progress / 180 - 1 / 2);
context.beginPath();
context.moveTo(700, 400);
context.arc(700, 400, 80, 0, Math.PI * 2, false);
context.closePath();
context.fillStyle = '#4BF41B';
context.fill();
context.beginPath();
context.moveTo(700, 400);
context.arc(700, 400, 80, -Math.PI * 1 / 2, progress_pi, false);
context.closePath();
context.fillStyle = 'red'
context.lineCap = 'round';
context.fill();
context.beginPath();
context.arc(700, 400, 65, 0, Math.PI * 2, false);
context.closePath();
context.fillStyle = 'white';
context.fill();
context.font = "bold 40pt Arial";
context.fillStyle = "red";
context.textAlign = "center";
context.textBaseline = 'middle';
context.fillText(currentSeconds, 700, 400);
// 抗锯齿
context.globalCompositeOperation = 'source-atop';
currentSeconds--;
}
</script>
</body>
</html>
