easyui的treegrid无法加载数据

Question

完完全全地用了示例代码
<table title="Folder Browser" class="easyui-treegrid" style="width:700px;height:250px"
                    data-options="
                        url: '__PUBLIC__/treegrid_data1.json',
                        method: 'get',
                        rownumbers: true,
                        idField: 'id',
                        treeField: 'name'
                    ">
                <thead>
                    <tr>
                        <th data-options="field:'name'" width="220">Name</th>
                        <th data-options="field:'size'" width="100" align="right">Size</th>
                        <th data-options="field:'date'" width="150">Modified Date</th>
                    </tr>
                </thead>
            </table>
结果竟然无法加载，用的是tp框架，treegrid_data1.json文件也正确引用了，结果如下