twoDirection.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>
	</head>

	<body>
		<div id="content">
			<div class="point">
				<button id="addDisk">发射</button>
			</div>
			<canvas id="canvas" width="400" height="300" style="background:#333"></canvas>
		</div>

		<script src="scripts/tool.js"></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
			// 球函数
			function Ball(x, y, radius,speed) {
				this.x = x;
				this.y = y;
				this.radius = radius;
				this.angle = 0;
				this.speed = speed;
			};
			// 事件
			document.getElementById("addDisk").addEventListener('click', function() {
				var speed = {x:5,y:4};
				balles.push(new Ball(0, 0, 10,speed));
			});

			var requestID = null;
			//绘制球
			function drawBall() {
				ctx.clearRect(0, 0, canvas.width, canvas.height);
				for(var i = 0; i < balles.length; i++) {
					var ball = balles[i];
					ctx.save();
					ctx.fillStyle = '#fff';
					ctx.beginPath();
					//重新计算球的位置
					ball.x += 5;
					ball.y += 4;
					if(ball.x >= (canvas.width-ball.radius*2) || ball.y >= (canvas.height-ball.radius*2)){
						balles.splice(i,1);
						i -= 1;
					};
					ctx.arc(ball.x, ball.y, ball.radius, 0, 2 * Math.PI, true);
					ctx.fill();
					ctx.restore();
				};
				requestID = requestAnimationFrame(drawBall);
			};
			window.onload = function() {
				drawBall();
			};
		</script>
	</body>

</html>