PC端三級欄目可以懸浮顯示，手機端只能顯示二級欄目，點擊右側下拉箭頭，不僅不顯示三級欄目，連二級欄目頁會自動關閉，代碼如下
<style type="text/css">
.dropdown-item:hover .dropdown-submenu{
visibility: hidden;
}
.dropdown-item li:hover .dropdown-submenu{
visibility: visible;
}
</style>
<nav class="navbar navbar-default navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar"><span class="sr-only">Toggle navigation</span><span class="icon-bar"></span><span class="icon-bar"></span><span class="icon-bar"></span></button>
<a href="{eyou:global name='web_cmsurl' /}/"><img src="{eyou:global name="web_logo" /}" class="logo" alt="{eyou:global name="web_name" /}" style="width:135%;height:110%;object-fit: cover;"/></a> </div>
<div id="navbar" class="navbar-collapse collapse">
<ul class="nav navbar-nav">
<li><a href="{eyou:global name='web_cmsurl' /}/" {eyou:eq name='$Think.const.CONTROLLER_NAME' value='Index'}class="cur"{/eyou:eq}>Home</a></li>
{eyou:channel type="top" id="field" currentstyle="cur" row='9'}
<li {eyou:notempty name="$field.children"}class="dropdown dropdown-item"{/eyou:notempty}> <a href="{$field.typeurl}" class="{$field.currentstyle}">{$field.typename}</a> {eyou:notempty name="$field.children"} <a href="{$field.typeurl}" id="app_menudown" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false"><span class="glyphicon glyphicon-menu-down btn-xs"></span></a>
<ul class="dropdown-menu nav_small" role="menu">
{eyou:channel name="$field.children" row="100" id="field2"}
<li {eyou:notempty name="$field.children"}class="dropdown"{/eyou:notempty} >
<a href="{$field2.typeurl}" class="{$field.currentstyle}">{$field2.typename}</a><a href="{$field2.typeurl}" id="app_menudown" class="dropdown-toggle threeji" data-toggle="dropdown" role="button" aria-expanded="false"><span class="glyphicon glyphicon-menu-down btn-xs"></span></a>
{eyou:notempty name="$field2.children"}
<ul class="dropdown-menu nav_small dropdown-submenu" role="menu" style="left:205px;top:-19px">
{eyou:models name="$field2.children" row="100" id="field3"}
<li><a href="{$field3.typeurl}" {$field.extends}>{$field3.typename}</a> </li>
{/eyou:models}
</ul>
{/eyou:notempty}
</li>
{/eyou:channel}
</ul>
{/eyou:notempty}</li>
{/eyou:channel}
</ul>
</div>
<!--/.nav-collapse --></div>
</nav>
