spring.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">
			.box {
				position: absolute;
				top: 10px;
				left: 450px;
			}
		</style>
	</head>

	<body>
		<div id="content">
			<div class="point">
				<button id="addDisk">增加球</button>
			</div>
			<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 spring = 0.03;
			var targetX = canvas.width/2;
			var vx = 0;
			var ax = 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;
			};
			balles.push(new Ball(10, canvas.height/2, 10));
			document.getElementById("addDisk").addEventListener('click', function() {
				animation();
			});
			//绘制球
			function animation() {
				ctx.clearRect(0, 0, canvas.width, canvas.height);
				drawBall();
				requestAnimationFrame(animation);
			};
			function drawBall(){
				for(var i = 0; i < balles.length; i++) {
					var ball = balles[i];
					ctx.fillStyle = '#fff';
					ctx.beginPath();
					ax = (targetX - ball.x) * spring;
					vx += ax;
					ball.x += vx;
					ctx.arc(ball.x, ball.y, ball.radius, 0, 2 * Math.PI, true);
					ctx.fill();
				};
			};

			window.onload = function() {
				drawBall();
			};
		</script>
	</body>

</html>