本人Ext菜鸟，有问题请高手指导

viewport = new Ext.Viewport({
        layout: 'border',
        <%if("browser".equalsIgnoreCase(type)){%>
        items:[toolbar,{
         xtype:'tabpanel',
         activeTab:0,
         id:'tabPanel1',
         region:'center',
         items:[orgTree,{
xtype:'panel',
title:'岗位列表',
id:'stationListTab',
html:'<iframe id="stationListFrame" width="100%" height="100%" src="'+contextPath+'/base/stationlevel/stationlist.jsp?type=browser&multi=<%=multi%>&idsin=<%=idsin%>&refid=<%=refid%>"></iframe>'
}]
        }]
        <%}else{%>
         items: [{id:'tabPanel1',items:orgTree}]
        <%}%>
});
orgTree.root.appendChild(oneNode);
viewport. findById('tabPanel1').setActiveTab('stationListTab');
本段代码当中，stationListTab既然已经存在与viewport的item的item下面了，为什么最后还要用viewport. findById('tabPanel1').setActiveTab('stationListTab');这个设置呢