extjs comobox 赋值有关问题

extjs comobox 赋值问题
var store = new Ext.data.SimpleStore({
 fields: ['value','state'],
 data:[
 ['1', '在岗'],
 ['0', '不在岗']
 ]
 });
      {
                                            columnWidth:.33,
                                            //默认时系统时间
                                            layout: 'form',
                                            items: [
                                                {
                                                    id:"state",
                                                    anchor:"98%" ,
                                                    labelAlign:'left',
                                                    xtype:'xcombo',
                                                    fieldLabel: '是否在岗',
                                                    store:store,
                                                    mode:'local',
                                                    allowBlank:true ,
                                                      hiddenName: 'value',
                                                    displayField: 'state',
                                                    valueField:'value',
                                                    name:'state',
                                                   // selectOnFocus:true,
                                                     allowBlank:false,
                                                    editable: false,
                                                    emptyText: '请选择是否在岗',
                                                    triggerAction: 'all',
                                                    readOnly:true
                                                }
                                            ]
                                        }

 现在传值到数据库传不过去，dbug调试发现 state 取不到值,不知道怎么回事

------解决思路----------------------
<input id="a" name="a"/>            

        $('#a').combobox({     
            url:XXXX
            valueField:'value',     
            textField:'label',
            onLoadSuccess: function () { //加载完成后,设置选中第一项
                XXXXXX;
        });
要注意下,URL返回的内容要已JSON格式传送回来,

LZ检查下你在后台获取的字符串是否为JSON格式,