ExtJS中运用HTML5 Canvas简单例子

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=\'#\'" /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!!!

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