我在html中有这个代码。调整大小后，菜单按钮将出现，但如果单击它将不会切换或显示菜单列表。
CODE
<div class="navbar navbar-default navbar-fixed-top" id="navHead">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">USJ-R Online Enrolment System</a>
</div>
<div class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li><a href="StudentPage.aspx">Home</a></li>
<li><a href="SubjectOffered.aspx">Subject Offered</a></li>
<li class="active"><a href="ApprovalArea.aspx">Approval Area</a></li>
<li><a runat="server" onserverclick="logout_Click" class="navbar-link">Logout</a> </li>
</ul>
</div><!--/.nav-collapse -->
</div>
</div>