Html 我的列表项未在导航栏中折叠

我对bootsrap有点陌生，我已经尝试了各种方法让UL类崩溃，但在重新调整视图端口的大小时它不会崩溃。下面是我写的代码

任何帮助都将不胜感激。谢谢大家!

<nav class="navbar navbar-default navbar-static-top' role='navigation' ">
<div class="fluid" >
    <!-- Brand and toggle get grouped for better mobile display -->
    <div class="navbar-header">
        <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
            <span class="sr-only">Toggle navigation</span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
        </button>



         <ul class="nav navbar-nav">
            <li><a href="">Projects</a></li>
            <li><a href="#">Freelancer</a></li>
            <li><a href="#">Inbox</a></li>
            <li><a href="#">My Account</a> </li>
        </ul>

     </div>
    </div>
</nav>

切换导航

别介意，伙计们，我刚找到原因。我需要将下面的div元素包装在UL上

    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">

代码如下所示

  <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
             <ul class="nav navbar-nav">
                <li><a href="">Projects</a></li>
                <li><a href="#">Freelancer</a></li>
                <li><a href="#">Inbox</a></li>
                <li><a href="#">My Account</a> </li>
            </ul>
                </div>