extjs 中，如何点击替换iframe中的内容

大家好，我想在左边的panel点击不同的panel，如这里面的“柔性配置按键”，会在中间“center”中显示不同的页面。中间"center"的html为iframe。请问如何修改代码呀，谢谢
JScript code

 Ext.onReady(function(){
       var viewport = new Ext.Viewport({
            layout:'border',
            items:[
                 /*{
                 region:'north',
                 contentEl:'north',
                 height:100
                 },*/
                 {
                    region:'west',
                    id:'west-panel',
                    title:'请选择业务',
                    split:true,
                    width: 200,
                    minSize: 175,
                    maxSize: 400,
                    collapsible: true,
                    margins:'0 0 0 5',
                    layout:'accordion',
                    listeners:{"click": function(){alert("haha");}},
                    layoutConfig:{
                        animate:true
                    },
                    items: [{
                        contentEl: 'west',
                        title:'柔性配置系统',
                        id:'test',
                        border:false,
                        handler:function(){alert("haha");},
                        iconCls:'nav'
                        
                    },{
                        title:'路由配置系统',
                        html:'<p>Some settings in here.</p>',
                        border:false,
                        iconCls:'nav'
                    }]
                },
                
                {
                region:'center',
                id:'test2',
                title:'',
                html:"<iframe scrolling='yes' width='100%' height='100%'  frameborder='0' src='http://www.sina.com.cn/'></iframe>"
                }
            
             ]
        });
       Ext.get("test").on('click', function() {
            alert("fds");
             [color=#FF0000]Ext.getCmp("test2").update("<iframe scrolling='yes' width='100%' height='100%'  frameborder='0' src='http://www.qq.cn/'></iframe>");[/color]
        });
    });

给Iframe加一个id，然后获取iframe设置src  
  {
  region:'center',
  id:'test2',
  title:'',
  html:"<iframe scrolling='yes' id='extIfr' width='100%' height='100%' frameborder='0' src='http://www.sina.com.cn/'></iframe>"
  }


JScript code

Ext.get("test").on('click', function() {
            alert("fds");
             document.getElementById('extIfr').src='http://www.qq.cn/';
        });