好的你好.
我决定开始使用HTML canvas来完成我的小项目.
还没有真正的开始.我只是学习Canvas的基础知识,我想要动画一个圆圈
<!DOCTYPE html>
<html>
<head>
<Meta charset="UTF-8">
<title>title</title>
<style>
body {
margin: 0px;
padding: 0px;
background: #222;
}
</style>
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body>
<canvas id="myCanvas" width="578" height="250"></canvas>
<script>
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var startAngle = 1.5 * Math.PI;
var endAngle = 3.2 * Math.PI;
var counterClockwise = false;
context.beginPath();
context.arc(x,y,radius,startAngle,endAngle,counterClockwise);
context.linewidth = 15;
// line color
context.strokeStyle = 'black';
context.stroke();
</script>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js" type="text/javascript"></script>
<script src="//ajax.googleapis.com/ajax/libs/mootools/1.4.5/mootools-yui-compressed.js" type="text/javascript"></script>
</body>
</html>
这是我努力实现的一个小提琴http://jsfiddle.net/oskar/Aapn8/.
我不会对“反弹”效果感到困惑.
但我基本上希望它在页面加载时绘制并停在所需的弧形角度
这是迄今为止我创造的小提琴.
http://jsfiddle.net/skerwin/uhVj6/
谢谢
解决方法
Live Demo
// requestAnimationFrame Shim
(function() {
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
window.requestAnimationFrame = requestAnimationFrame;
})();
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var endPercent = 85;
var curPerc = 0;
var counterClockwise = false;
var circ = Math.PI * 2;
var quart = Math.PI / 2;
context.linewidth = 10;
context.strokeStyle = '#ad2323';
context.shadowOffsetX = 0;
context.shadowOffsetY = 0;
context.shadowBlur = 10;
context.shadowColor = '#656565';
function animate(current) {
context.clearRect(0,canvas.width,canvas.height);
context.beginPath();
context.arc(x,-(quart),((circ) * current) - quart,false);
context.stroke();
curPerc++;
if (curPerc < endPercent) {
requestAnimationFrame(function () {
animate(curPerc / 100)
});
}
}
animate();
基本上我使用了你发布的演示链接中的相同公式.然后我添加了一个动画函数,调用时会更新圆圈,直到达到所需的结束百分比.
动画在requestAnimationFrame不断调用,这是使用canvas进行任何动画的首选方式.每次调用动画时,当前百分比增加1,然后用于重绘弧.