Another way to display only one component between form and grid is to wrap a panel around them.
<div id="p1" class="easyui-panel" fit="true" closed="true">...</div>
<div id="p2" class="easyui-panel" fit="true">...</div>
The code below shows how to display panel p1 and hide panel p2.
$('#p1').panel('open');
$('#p2').panel('close');