我在基于在线教程的画布元素搞乱了,并构建了以下页面,here。帆布的fps无意中加速?
这里是我的标记:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Canvas Game</title>
<link rel="stylesheet" href="style.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
<script src="script.js"></script>
</head>
<body>
<header>
<h1>Cool Canvas Bouncing Effect!</h1>
<p>Which would you like to see bounce around?</p>
<input id="beachBallButton" type="button" value="Beach Ball" />
<input id="avatarButton" type="button" value="Avatar" />
</header>
<br />
<canvas id="myCanvas" width="600" height="400">
Your browser does not support canvas!
</canvas>
</body>
</html>
这里是我的JavaScript:
$(document).ready(function() {
const FPS;
var x = 0;
var y = 0;
var xDirection = 1;
var yDirection = 1;
var image = new Image();
image.src = null;
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
$('#avatarButton').click(function() {
x = 0;
y = 0;
FPS = 30;
image.src = 'avatar.png';
setInterval(draw, 1000/FPS);
function draw() {
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.fillRect(0,0,canvas.width,canvas.height);
ctx.drawImage(image, x, y);
x += 1 * xDirection;
y += 1 * yDirection;
if (x >= 500)
{
x = 500;
xDirection = -1;
}
else if (x <= 0)
{
x = 0;
xDirection = 1;
}
if (y >= 300)
{
y = 300;
yDirection = -1;
}
else if (y <= 0)
{
y = 0;
yDirection = 1;
}
}
});
$('#beachBallButton').click(function() {
x = 0;
y = 0;
FPS = 60;
image.src = 'beachball.png';
setInterval(draw, 1000/FPS);
function draw() {
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.fillRect(0,0,canvas.width,canvas.height);
ctx.drawImage(image, x, y);
x += 5 * xDirection;
y += 5 * yDirection;
if (x >= 450)
{
x = 450;
xDirection = -1;
}
else if (x <= 0)
{
x = 0;
xDirection = 1;
}
if (y >= 250)
{
y = 250;
yDirection = -1;
}
else if (y <= 0)
{
y = 0;
yDirection = 1;
}
}
});
});
现在,假设你点击Avatar
按钮,然后点击Beach Ball
之后,FPS是加快了。但是,我在两个函数的click
函数内重置了FPS变量。我还重置了x
和y
变量。
此外,我可以继续点击相同的按钮,速度也会显着增加。
有人可以帮助解释为什么会发生这种情况吗?
谢谢!
哇,我怎么能错过自己想要分配常数的变量。我从网上的一个教程调整了这个,所以它不是一个问题之前...... xD谢谢! – Qcom 2011-02-15 23:07:34