extjs4 继承类使用initComponet 和constructor

IndexPage=Ext.define('IndexPage',{extend:'Ext.Viewport',center:Ext.create('Ext.TabPanel',{id:'MainTab',region:'center',autoScroll:true,items:{title:'标题',html:'首页'}}),//initComponent: function() {//        var me = this;//        Ext.applyIf(me,{//        layout:'border',//        items:[this.center]//        });//        me.callParent(arguments);//    }constructor:function(){IndexPage.superclass.constructor.call(this,{layout:'border',        items:[this.center]})}})