<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>帆布小球碰壁效果</title>
<style>
canvas {
border:2px dotted #ccc;
}
</style>
</head>
<body>
<canvas id="canvas" width="300" height="450"></canvas>
<script type="text/javascript">
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var raf;
var ball = {
x: 100,
y: 100,
vx: 5,
vy: 2,
radius: 25,
color: 'blue',
draw: function() {
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
ctx.closePath();
ctx.fillStyle = this.color;
ctx.fill();
}
};
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
ball.draw();
ball.x += ball.vx;
ball.y += ball.vy;
if (ball.y + ball.vy > canvas.height ||
ball.y + ball.vy < 0) {
ball.vy = -ball.vy;
}
if (ball.x + ball.vx > canvas.width ||
ball.x + ball.vx < 0) {
ball.vx = -ball.vx;
}
raf = window.requestAnimationFrame(draw);
}
canvas.addEventListener('mouseover', function(e) {
raf = window.requestAnimationFrame(draw);
});
canvas.addEventListener("mouseout", function(e) {
window.cancelAnimationFrame(raf);
});
ball.draw();
</script>
</body>
</html>