下面这是官网的例子 我运行怎么 datagrid没有绑定到值？
html页面。
- HTML code
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>DataGrid Footer Row - jQuery EasyUI Demo</title>
<link rel="stylesheet" type="text/css" href="../themes/default/easyui.css">
<link rel="stylesheet" type="text/css" href="../themes/icon.css">
<link rel="stylesheet" type="text/css" href="demo.css">
<script type="text/javascript" src="../jquery-1.6.min.js"></script>
<script type="text/javascript" src="../jquery.easyui.min.js"></script>
<script type="text/javascript">
$(function(){
$('#tt').datagrid({
url: 'datagrid_data3.json',
title: '测试TEST',
width: 700,
height: 220,
fitColumns: true,
nowrap:false,
rownumbers:true,
showFooter:true,
columns:[[
{field:'itemid',title:'Item ID',width:80},
{field:'productid',title:'Product ID',width:120},
{field:'listprice',title:'List Price',width:80,align:'right'},
{field:'unitcost',title:'Unit Cost',width:80,align:'right'},
{field:'attr1',title:'Attribute',width:250},
{field:'status',title:'Status',width:60,align:'center'}
]]
});
});
</script>
</head>
<body>
<h2>DataGrid - Footer Row</h2>
<div class="demo-info" style="margin-bottom:10px">
<div class="demo-tip icon-tip"></div>
<div>Display summary information in footer rows.</div>
</div>
<table id="tt"></table>
</body>
</html>
JSON数据
{"total":28,"rows":[
{"productid":"FI-SW-01","unitcost":10.00,"status":"P","listprice":36.50,"attr1":"Large","itemid":"EST-1"},
{"productid":"K9-DL-01","unitcost":12.00,"status":"P","listprice":18.50,"attr1":"Spotted Adult Female","itemid":"EST-10"},
{"productid":"RP-SN-01","unitcost":12.00,"status":"P","listprice":28.50,"attr1":"Venomless","itemid":"EST-11"},
{"productid":"RP-SN-01","unitcost":12.00,"status":"P","listprice":26.50,"attr1":"Rattleless","itemid":"EST-12"},
{"productid":"RP-LI-02","unitcost":12.00,"status":"P","listprice":35.50,"attr1":"Green Adult","itemid":"EST-13"},
{"productid":"FL-DSH-01","unitcost":12.00,"status":"P","listprice":158.50,"attr1":"Tailless","itemid":"EST-14"},
{"productid":"FL-DSH-01","unitcost":12.00,"status":"P","listprice":83.50,"attr1":"With tail","itemid":"EST-15"},
{"productid":"FL-DLH-02","unitcost":12.00,"status":"P","listprice":63.50,"attr1":"Adult Female","itemid":"EST-16"},