ExtJS4.x下拉框默认第一条数据

Question

加载窗体时，显示加载的第一条数据更新到下拉框中；现在是得到了第一条数据，alert出来，但是如何更新到我的这个下拉框控件上呢？     xtype:'combo',  
    id:'xxID',  
    name:'xx',  
    store:xxstore,         
valueField:'name',                                                                     displayField:'text',                                
forceSelection :true,    
    lazyInit:false,    
    editable  : false,    
    triggerAction: 'all',  
    width : 150,  
    listeners:{  
       afterrender:function(combo1){  
          var firstValue = xxstore.getAt(0).get('text');  
                                                                                             //alert(firstValue);  
                                                                                            combo1.setValue(firstValue);  
       }  
    }  

Answer 1

var myRecord=Ext.data.Record.create([{
name:"steps"
},{
name:"tools"
},{
name:"parts"
},{
name:"prdId"
},{
name:"mems"
},{
name : "qty",
type : "double"
},{
name:"methods"
},{
name : "workhours",
type : "double"
},{
name:"qther1"
},{
name:"qther2"
}]);
xxstore.insert(0,myRecord)

Answer 2

listeners:{  
       afterrender:function(combo1){  
          var firstValue = xxstore.getAt(0).get('name'); //用valueField
          combo1.setValue(firstValue);  
       }