Extjs:Grid没显示后台返回的Json数据

success: function(response){

    var rs = Ext.JSON.decode(response.responseText);

    Ext.Msg.alert("按钮", rs.data);

 // process server response here

    var store = new Ext.data.Store({  

    data:rs.data,

    fields:['provider','location','currency'

,'startnum1','startunit1','endnum1','endunit1','price1','priceunit1'

,'startnum2','startunit2','endnum2','endunit2','price2','priceunit2'

,'startnum3','startunit3','endnum3','endunit3','price3','priceunit3']  

    });  

    console.info(rs);

    this.getSGrid().reconfigure(store);

    console.info(this.getSGrid().store.data);

    //看到store有很多条记录但都是空的

}

后台返回的数据rs.data是：
[{"endunit3":"TB","endnum1":"1.0","endnum2":"10.0","endunit2":"TB","endunit1":"TB","provider":"Google","endnum3":"100.0","startnum3":"10.0","startnum2":"1.0","startnum1":"0.0","currency":"dollar","startunit1":"TB","startunit3":"TB","startunit2":"TB"},{"endunit3":"TB","endnum1":"1.0","endnum2":"10.0","endunit2":"TB","endunit1":"TB","provider":"Google","endnum3":"100.0","startnum3":"10.0","startnum2":"1.0","startnum1":"0.0","currency":"dollar","startunit1":"TB","startunit3":"TB","startunit2":"TB"}]


Grid绘制出来但是没有数据。
Grid的代码：

{

    xtype:'grid',

    id:'sgrid',

    store:{

        fields: ['provider','location','currency'

            ,'startnum1','startunit1','endnum1','endunit1','price1','priceunit1'

            ,'startnum2','startunit2','endnum2','endunit2','price2','priceunit2'

            ,'startnum3','startunit3','endnum3','endunit3','price3','priceunit3']

    },

    title: "search result",

    width: 1000,

    autoHeight: true,

    columns:[

    {text: "provider", width: 80, dataIndex: "provider", tooltip: "provider"},

    {text: "location", width: 80, dataIndex: "location", align: "center"},

    {text: "currency", width: 50, dataIndex: "currency"},

    {text: "startnum1", width: 50, dataIndex: "startnum1", align: "center"},