HTML5 Canvas不在浏览器中显示

Question

I'm following this tutorial to learn HTML5 game development using javascript and jQuery. 我正在按照本教程学习使用javascript和jQuery进行HTML5游戏开发。 However, I've already come across a problem. 但是，我已经遇到了一个问题。 When I run the HTML page that my js file is referenced from, nothing loads, and is just a blank screen. 当我运行引用我的js文件的HTML页面时，没有任何内容加载，只是一个空白屏幕。 Here is the code for both files. 这是两个文件的代码。 Note that I haven't gotten very far in the tutorial. 请注意，我在教程中并没有走得太远。

index.html 的index.html

<HTML>
<head>
</head>
<body>
<p>HTML5 and jQuery Tests</p>
<script type ="text/javascript" src="test.js"></script>
</body>
</HTML>

test.js test.js

var CANVAS_WIDTH = 480;
var CANVAS_HEIGHT = 320;

var canvasElement = $("<canvas width='" + CANVAS_WIDTH +"' height='" + CANVAS_HEIGHT +        "'></canvas>");
var canvas = canvasElement.get(0).getContext("2d");
canvasElement.appendTo('body');
var FPS = 30;
setInterval(function() {
update();
draw();
}, 1000/FPS);
function draw() {
canvas.fillStyle = "#000"; 
canvas.fillText("hello.", 50, 50);
}

Any help would be greatly appreciated! 任何帮助将不胜感激！ Also, am I allowed to ask questions about this code in this forum, on the same thread, or do I have to stat another? 另外，我可以在这个论坛上，在同一个帖子上提出有关此代码的问题，或者我是否需要统计另一个？

Thanks! 谢谢！ ~Carpetfizz 〜Carpetfizz

Answer 1

You don't have an update function to call. 您没有可以调用的update功能。 When the setInterval fires (which is ~32ms after the script loads), you're getting an error. 当setInterval触发时（脚本加载后大约32ms），您将收到错误。

You need to add jQuery. 你需要添加jQuery。
It's a library that was written to make working with HTML easier. 这是一个编写的库，可以更轻松地使用HTML。
It needs to exist above where test.js does. 它需要存在于 test.js所在的位置test.js 。

You can either download your own copy of it, or link to a copy elsewhere on the net - both will work fine. 您可以下载自己的副本，也可以链接到网上其他地方的副本 - 两者都可以正常工作。

$ is used by jQuery as a function to intelligently grab different kinds of items: HTML, JS, etc, and return JS objects with helpful functions for working with whatever you asked for. $被jQuery用作智能地抓取不同类型的项目的函数：HTML，JS等，并返回JS对象以及有用的函数来处理您要求的任何内容。

Anyway, the update would still have caused an error, it was just second in line, behind the missing script. 无论如何， update仍然会导致错误，它只是排在第二位，在缺失的脚本后面。

HTML5 Canvas不在浏览器中显示

问题描述

1 个解决方案

解决方案1
2 已采纳 2013-03-31 04:35:54

HTML5 Canvas不在浏览器中显示

问题描述

1 个解决方案

解决方案1 2 已采纳 2013-03-31 04:35:54

解决方案1
2 已采纳 2013-03-31 04:35:54