在ExtJS的Panel组件上使用HTML5的Canvas对象画图
的简单例子，效果如下：
怎么运行源代码：
新建两个文件，分别命名为mydemo.html, mydemo.js以后，将对应的HTML源代码
与JavaScript代码copy到各自的文件中，在同一目录下使用Google Chrome浏览器
或者IE9.0打开html文件即可看到效果！
HTML的代码如下：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Example</title>
<link rel="stylesheet" type="text/css" href="../../resources/css/ext-all.css" />
<link rel="stylesheet" type="text/css" href="../shared/example.css" />
<script type="text/javascript" src="../../bootstrap.js"></script>
<script language="javascript" src="mydemo.js"></script>
</head>
<body>
<h1>ExtJS with HTML5 Demo</h1>
<p>The js is not minified so it is readable. See <a href="mydemo.js">source code</a>.</p>
<div id="my-demo"></div>
</body>
</html>
ExtJS的代码如下：
/**
* HTML5 Canvas Demo
*/
// create namespace
Ext.namespace('Test');
// create application
Test.app = function() {
return {
// public methods
init: function() {
var grid = new Ext.Panel({
renderTo: 'my-demo',
title:'Simple HTML5 Canvas Demo',
bodyStyle: 'padding: 10px;',
borders: true,
plain: true,
xtype: 'panel',
width:400,
height:400,
html: '<canvas id="canvas" width="400" height="400"></canvas>'
});
}, // end of init
onDraw: function() {
this.canvas = document.getElementById('canvas');
this.ctx = this.canvas.getContext("2d");
// create a blank image data
var canvas2Data = this.ctx.createImageData(this.canvas.width, this.canvas.height);
for ( var x = 0; x < canvas2Data.width; x++) {
for ( var y = 0; y < canvas2Data.height; y++) {
// Index of the pixel in the array
var idx = (x + y * canvas2Data.width) * 4;
// assign gray scale value
var distance = Math.sqrt((x - canvas2Data.width / 2) * (x - canvas2Data.width / 2) + (y - canvas2Data.height / 2) * (y - canvas2Data.height / 2));
var cvalue = (128.0 + (128.0 * Math.sin(distance / 8.0)));
canvas2Data.data[idx + 0] = cvalue; // Red channel
canvas2Data.data[idx + 1] = cvalue; // Green channel
canvas2Data.data[idx + 2] = cvalue; // Blue channel
canvas2Data.data[idx + 3] = 255; // Alpha channel
}
}
this.ctx.putImageData(canvas2Data, 0, 0); // at coords 0,0
// draw author infomation
this.ctx.fillStyle = "red";
this.ctx.font = "24px Times New Roman";
this.ctx.fillText("HTML5 Demo - by gloomyfish ", 50, 60);
}
};
}();
// end of app
Ext.onReady(function(){
Test.app.init();
Test.app.onDraw()
// alert('ext.onready')
});
// Ext.onReady(Test.app.init, Test.app);
一定要有ExtJS的库文件支持！！！
