Easyui 二级菜单

        <div class="fitem">
            <label>所在城市:</label>
            <input id="cityId" name="cityId" style="width:200px" class="easyui-combobox"  >
        </div>
        <div class="fitem">
            <label>所在区域:</label>
            <input id="areaId" name="areaId" style="width:200px"  class="easyui-combobox" >
        </div>

 $('#cityId').combobox({
        url:'/yami/backend/city.getCityJson.do',
        valueField:'id',
        textField:'name',
        width:200,
        panelHeight:100,
        editable:false,
        required:true,
        onChange:function(cityId){
            if(cityId==null){
                return;
            }
            $('#areaId').combobox('clear');
            $('#areaId').combobox({
                valueField:'id',
                textField:'name',
                url:'/yami/backend/area.getAreaJson.do?cityId='+cityId,
                width:200,
                panelHeight:100,
                required:true,
                editable:true//不可编辑。仅仅能选择
            });
        }
    });