canvas實現的隨機生成漂浮小球程式碼例項

admin發表於2017-02-17
Canvas隨機

分享一段程式碼例項，它實現了隨機生成漂浮小球的功能。

程式碼例項如下:

[HTML] 純文字檢視 複製程式碼
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>螞蟻部落</title>
</head>
<body>
<canvas id="canvas" width="500" height="500"></canvas>
<script>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var screenWidth = document.documentElement.offsetWidth;
var screenHeight = document.documentElement.offsetHeight;
 
canvas.width = screenWidth;
canvas.height = screenHeight;
//隨機函式
function rand(min, max) {
  return Math.floor(Math.random() * (max - min) + min);
 
}
 
function Ball() {
  this.r = rand(5, 30);
  //圓心
  this.x = rand(this.r, screenWidth - this.r);
  this.y = rand(this.r, screenHeight - this.r);
  //顏色
  this.color = "rgba(" + rand(0, 256) + "," + rand(0, 256) + "," + rand(0, 256) + "," + Math.random() + ")";
  //速度
  this.speedX = rand(1, 10);
  this.speedY = rand(1, 10);
}
Ball.prototype.move = function() {
  this.x += this.speedX * (rand(0, 2) > 1 ? 1 : -1);
  this.y += this.speedY * (rand(0, 2) > 1 ? 1 : -1);
  if (this.x >= screenWidth - this.r) {
    this.speedX *= -1;
  }
  if (this.x <= this.r) {
    this.speedX *= -1;
  }
  if (this.y >= screenHeight - this.r) {
    this.speedY *= -1;
  }
  if (this.y <= this.r) {
    this.speedY *= -1;
  }
 
}
 
Ball.prototype.draw = function() {
  ctx.beginPath();
  ctx.fillStyle = this.color;
  ctx.arc(this.x, this.y, this.r, 0, Math.PI * 2, true);
  ctx.closePath();
  ctx.fill();
}
 
var balls = [];
for (var i = 0; i < 100; i++) {
  var ball = new Ball();
  balls.push(ball);
  ball.draw();
}
 
function move() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  for (var i = 0; i < balls.length; i++) {
    var ball = balls<i>;
    ball.draw();
    ball.move();
  }
  window.requestAnimationFrame(move);
}
move();
</script>
</body>
</html>

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