Bootstrap框架如何设置使导航栏始终固定在页面顶部

引入文件，这是需要自己去官网下载的

<link rel="stylesheet" type="text/css" href="../css/bootstrap.min.css" />		
<script src="../js/jquery.js" type="text/javascript" charset="utf-8"></script>
<script src="../js/bootstrap.min.js" type="text/javascript" charset="utf-8"></script>

HTML部分
navbar-fixed-top：使导航条固定在头部

<div class="container-fluid">
            <div class="row">
                <nav class="navbar navbar-fixed-top navbar-default">
                    <div class="container">
                        <!-- 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>
                            <a class="navbar-brand" href="#"><b>xx学院</b></a>
                        </div>

                        <!-- Collect the nav links, forms, and other content for toggling -->
                        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                            <ul class="nav navbar-nav navbar-right">
                                <li class="dropdown">
                                    <li>
                                        <a href="index.html"><b>xx首页</b> <span class="sr-only">(current)</span></a>
                                    </li>
                                    <li>
                                        <a href="index.html"><b>xx博客</b> <span class="sr-only">(current)</span></a>
                                    </li>
                                    <li>
                                        <a href="index.html"><b>前端开发</b> <span class="sr-only">(current)</span></a>
                                    </li>
                                    <li>
                                        <a href="index.html"><b>最新课程</b> <span class="sr-only">(current)</span></a>
                                    </li>
                                    <li>
                                        <a href="index.html"><b>移动APP</b> <span class="sr-only">(current)</span></a>
                                    </li>
                                    <li>
                                        <a href="#"><b>联系我们</b></a>
                                    </li>
                                </li>
                            </ul>
                        </div>
                        
                    </div>
                
                </nav>
            </div>

        </div>