canvas小球碰壁效果

螞蟻小編發表於2018-06-02
Canvas
分享一段程式碼例項，它利用canvas實現了小球碰壁效果。

程式碼例項如下:

[HTML] 純文字檢視 複製程式碼執行程式碼
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>螞蟻部落</title>
<style>
canvas {
  border:2px dotted #ccc;
}
</style>
</head>
<body>
<canvas id="canvas" width="550" 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>

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