Question

我正在尝试构建一个导航栏，其中一些具有下拉菜单，我尝试了引导程序，并尝试复制并通过同一类，但是没有用。试图复制那里的一些作品，但没有用，我不知道如何更改它。而且我在html和css中有点新，我正在尝试自己建立一些东西。请帮我这是代码：

* {
    box-sizing: border-box;
  }

  body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
  }

  .topnav {
    overflow: hidden;
    background-color: #e9e9e9;
  }

  .topnav a {
    float: left;
    display: block;
    color: black;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 17px;
  }

  .topnav a:hover {
    background-color: #ddd;
    color: black;
  }

  .topnav a.active {
    background-color: #2196F3;
    color: white;
  }

  .topnav .login-container {
    float: right;
  }

  .topnav input[type=text] {
    padding: 6px;
    margin-top: 8px;
    font-size: 17px;
    border: none;
    width: 120px;
  }

  .topnav .login-container button {
    float: right;
    padding: 6px 10px;
    margin-top: 8px;
    margin-right: 16px;
    background-color: #555;
    color: white;
    font-size: 17px;
    border: none;
    cursor: pointer;
  }
  @media screen and (max-width: 600px) {
    .topnav .login-container {
      float: none;
    }
    .topnav a,
    .topnav input[type=text],
    .topnav .login-container button {
      float: none;
      display: block;
      text-align: left;
      width: 100%;
      margin: 0;
      padding: 14px;
    }
    .topnav input[type=text] {
      border: 1px solid #ccc;
    }
  }

  .dropup,
  .dropdown {
    position: relative;
  }
  
  .dropdown-toggle::after {
    display: inline-block;
    width: 0;
    height: 0;
    margin-left: 0.3em;
    vertical-align: middle;
    content: "";
    border-top: 0.3em solid;
    border-right: 0.3em solid transparent;
    border-left: 0.3em solid transparent;
  }
  
  .dropdown-toggle:focus {
    outline: 0;
  }
  
  .dropup .dropdown-toggle::after {
    border-top: 0;
    border-bottom: 0.3em solid;
  }
  
  .dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    z-index: 1000;
    display: none;
    float: left;
    min-width: 10rem;
    padding: 0.5rem 0;
    margin: 0.125rem 0 0;
    font-size: 1rem;
    color: #292b2c;
    text-align: left;
    list-style: none;
    background-color: #fff;
    -webkit-background-clip: padding-box;
            background-clip: padding-box;
    border: 1px solid rgba(0, 0, 0, 0.15);
    border-radius: 0.25rem;
  }
  
  .dropdown-divider {
    height: 1px;
    margin: 0.5rem 0;
    overflow: hidden;
    background-color: #eceeef;
  }
  
  .dropdown-item {
    display: block;
    width: 100%;
    padding: 3px 1.5rem;
    clear: both;
    font-weight: normal;
    color: #292b2c;
    text-align: inherit;
    white-space: nowrap;
    background: none;
    border: 0;
  }
  
  .dropdown-item:focus, .dropdown-item:hover {
    color: #1d1e1f;
    text-decoration: none;
    background-color: #f7f7f9;
  }
  
  .dropdown-item.active, .dropdown-item:active {
    color: #fff;
    text-decoration: none;
    background-color: #0275d8;
  }
  
  .dropdown-item.disabled, .dropdown-item:disabled {
    color: #636c72;
    cursor: not-allowed;
    background-color: transparent;
  }
  
  .show > .dropdown-menu {
    display: block;
  }
  
  .show > a {
    outline: 0;
  }
  
  .dropdown-menu-right {
    right: 0;
    left: auto;
  }
  
  .dropdown-menu-left {
    right: auto;
    left: 0;
  }
  
  .dropdown-header {
    display: block;
    padding: 0.5rem 1.5rem;
    margin-bottom: 0;
    font-size: 0.875rem;
    color: #636c72;
    white-space: nowrap;
  }
  
  .dropdown-backdrop {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 990;
  }
  
  .dropup .dropdown-menu {
    top: auto;
    bottom: 100%;
    margin-bottom: 0.125rem;
  }

<html>
  <head>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.11.0/umd/popper.min.js" integrity="sha384-b/U6ypiBEHpOf/4+1nzFpr53nxSS+GLCkfwBdFNTxtclqqenISfwAzpKaMNFNmj4" crossorigin="anonymous"></script>

  </head>
<body>
  <div class="topnav">
    <a class="active" href="#home">Home</a>
    <a href="#about">About</a>
    <a href="#contact">Contact</a>
    <div class="login-container">
      <form >
          <div class="dropdown">
          <button type="button" class="btn btn-danger dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
            Action
          </button>
          <div class="dropdown-menu">
            <a class="dropdown-item" href="#">Action</a>
            <a class="dropdown-item" href="#">Another action</a>
            <a class="dropdown-item" href="#">Something else here</a>
            <div class="dropdown-divider"></div>
            <a class="dropdown-item" href="#">Separated link</a>
          </div>
        </div>
      </form>
    </div>
  </div>

</body>

</html>

带有下拉菜单4和引导程序4的导航栏不起作用

0 个答案: