EXT的formfield中combo下拉框为textfield赋值

{
columnWidth : 0.2,
layout : 'form',
labelWidth : 70,
items : {
fieldLabel : '维修材料',    //repair_material
width : 70,
name  : 'repair_material',
xtype:'combo',
editable : false,
mode  :'local',
triggerAction:'all',
allowBlank:false,
store : matStore,
displayField: 'cname',
valueField  : 'cid',
//emptyText:'无',//默认值
listeners:{
select : function(combo, record,index){
//alert(record.data.cid);
//alert(combo.value);
Ext.Ajax.request({
url: 'warrantyServiceAction!selectDanwei.shtml',
method: 'POST',
params: {material_name_test:record.data.cname},
success: function(response) {
//alert(response.responseText);
if(response.responseText=="null"){
Ext.getCmp("repair_danwei").setValue("无");
}else{
Ext.getCmp("repair_danwei").setValue(response.responseText);
}

}
});
},
/*
render:function(obj) {
var fontNew = document.createElement("font");
fontNew.setAttribute("color","black");
var redStar = document.createTextNode('小时');
fontNew.appendChild(redStar);
obj.el.dom.parentNode.appendChild(fontNew);
}
*/
}

}
},{
columnWidth : 0.2,
layout : 'form',
labelWidth : 30,
items : {
fieldLabel : '单位',    //repair_material
width : 70,
name  : 'repair_danwei',
id: 'repair_danwei',
xtype:'textfield',
editable : false,
readOnly:true

}
},