EasyUI Combotree 实现异步加载树节点

<tr>
<th>父导航名称</th>
<td>
<input id="R_SID" name="R_SID" value="${(record.R_SID!)!}" data-options="required:true">
</td>
</tr>

$('#R_SID').combotree({
url: "${WEBPATH!}/bo/eSYS_NAV/tree.html",
panelHeight: '180px',
onBeforeExpand: function (node) {
$('#R_SID').combotree("tree").tree("options").url = "${WEBPATH!}/bo/eSYS_NAV/tree.html?R_SID=" + node.id;
}
});