html - 折叠的导航栏仅显示在小屏幕尺寸的 Bootstrap 上

Question

我正在尝试实现一个在小型设备上折叠的导航栏。这工作正常。

但是，在中型和大型屏幕上，导航栏根本不显示。我希望导航栏对于中型和大型屏幕看起来像普通导航栏，然后折叠成小型设备的导航栏按钮。我正在遵循 Bootstrap 模板，但不知道为什么导航栏根本不显示。

  <div class = "container">

     <nav class="navbar navbar-default" >
            <div class="navbar-header">
                <a class="navbar-brand" href="#">
                    <img alt="logo" src="logo.png" width="250px;">
                </a>
                <button class="navbar-toggle collapsed" type="button" data-toggle="collapse" data-target="#collapse-navbar" aria-expanded="false" aria-controls="navbar">
                    &#9776;
                </button>
            </div>
            <div class="navbar-collapse collapse" id="collapse-navbar">    
                <ul class="nav navbar-nav">
                    <li class= "nav-item"><a class= "nav-link active" href="#">Home</a></li>
                    <li class= "nav-item"><a class= "nav-link" href="#">Build</a></li>
                    <li class= "nav-item"><a class= "nav-link" href="#">About</a></li>
                </ul>
            </div>
     </nav> 
</div>

这是一个代码笔链接:https://codepen.io/gkunthara/pen/VWdrYj

Answer 1

您正在使用 bootstrap 3 标记并链接到 bootstrap 4 css 或者链接到 bootstrap 3 的 css 和 javascript，如下所示:

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>

或者像这样将导航栏标记更改为 bootstrap 4 的标记:

<nav class="navbar navbar-toggleable-md navbar-light bg-faded">
  <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <a class="navbar-brand" href="#">
    <img alt="logo" src="logo.png" width="250px;">
  </a>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Build</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">About</a>
      </li>
    </ul>
  </div>
</nav>