sencha touch 2 tabpanel load external html

app.js

// You should use Ext.application, not Ext.setup
Ext.application({
	name: 'SampleLoad',
	requires: ['Ext.Ajax'],
	launch: function () {
		Ext.create("Ext.tab.Panel", {
			fullscreen: true,
			tabBarPosition: 'bottom',
			items: [
				{
					id: 'welcome-tab',
					title: 'Home',
					iconCls: 'home',

// dummy text: to be overwritten with external html
					html: 'Welcome' 

				},
				{
					id: 'sample-tab',
					title: 'aaaa',
					iconCls: 'reply',

// dummy text: to be overwritten with external html
					html: 'aaaaaaaa'
				}
			]
		});
		Ext.Ajax.request({
			url: 'sample.html', // place into same dir with app.js
			method: 'GET',
			callback: function(options, success, response) {
				Ext.ComponentQuery.query('#sample-tab')[0].setHtml( response.responseText );
			}
		});
		Ext.Ajax.request({
			url: 'welcome.html', // place into same dir with app.js
			method: 'GET',
			callback: function(options, success, response) {
				Ext.ComponentQuery.query('#welcome-tab')[0].setHtml( response.responseText );
			}
		});
	}
});