rotate.html


<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />
		<title></title>

		<style id="stylesheet">
		</style>
	</head>

	<body>
		<div id="content">
			<canvas id="canvas" width="400" height="300" style="background:#333"></canvas>
		</div>

		<script src="scripts/tool.js?id=1"></script>
		<script id="scripts">
			var canvas = document.getElementById('canvas');
			var ctx = canvas.getContext('2d');
			var centerX = Math.floor(canvas.width / 2);
			var centerY = Math.floor(canvas.height / 2);

			var balles = []; //存放页面上的球
			var angle = 0;
			var vr = 0.05;
			var radius = 0;
			// 球函数
			function Ball(x, y, radius, speed) {
				this.x = x;
				this.y = y;
				this.radius = radius;
				this.angle = 0;
				this.speed = speed;
			};
			function animation() {
				ctx.clearRect(0, 0, canvas.width, canvas.height);
					ctx.fillStyle = '#fff';
				balles.forEach(function(ball,i){
					ball.x = centerX + Math.cos(angle) * radius;
					ball.y = centerY + Math.sin(angle) * radius;
					angle += vr;
					ctx.beginPath();
					ctx.arc(ball.x, ball.y, ball.radius, 0, 2 * Math.PI, true);
					ctx.fill();
				});
				ctx.beginPath();
				ctx.strokeStyle = '#fff';
				ctx.arc(centerX,centerY,radius,0,2*Math.PI,true);
				ctx.stroke();
				ctx.beginPath();
				ctx.arc(centerX,centerY,2,0,2*Math.PI,true);
				ctx.fill();
				requestAnimationFrame(animation);
			};
			
			window.onload = function() {
				balles.push(new Ball(centerX - 50,centerY - 50,10));
				var x = balles[0].x - centerX;
				var y = balles[0].y - centerY;
				radius = Math.floor(Math.sqrt(x*x+y*y));
				animation();
			};
		</script>
	</body>

</html>