求助，关于Ext.BasicDialog简单Demo的实现

<link rel="stylesheet" type="text/css"
href="Ext/resources/css/ext-all.css">
<script type="text/javascript" src="Ext/ext-base.js"></script>
<script type="text/javascript" src="Ext/ext-all.js"></script>
<script type="text/javascript" src="Ext/ext-all-debug.js"></script>
<script>
                       function meetingElse(){
function InitDialog() {
     var dialog = new Ext.BasicDialog("hello-dlg", { 
          id: "hello-dialog",
            title: "Hello",
          autoTabs:true,
          width:500,
          height:300,
          shadow:true,
          minWidth:300,
          minHeight:250,
          //proxyDrag: true
  });
  dialog.addKeyListener(27, dialog.hide, dialog);
  dialog.addButton('Submit', dialog.hide, dialog).disable();
  dialog.addButton('Close', dialog.hide, dialog);
  
  Ext.ComponentMgr.register(dialog);
}
 function OnButtonClick() {
  var dialog = Ext.getCmp("hello-dialog");
  dialog.show();
}
Ext.onReady(InitDialog);
     }</script>                 html里面写了一个<div id="dialog"></div>
但是在firefox里面运行，抛出Ext.BasicDialog is not a constructor异常，求助，在线等