如何在 Bootstrap 中制作这种下拉菜单 [关闭]答案

【问题标题】：how to make such kind of dropdown in Bootstrap [closed]如何在 Bootstrap 中制作这种下拉菜单 [关闭]
【发布时间】：2017-09-03 19:44:02
【问题描述】：

我用 bootstrap 做了一个简单的导航栏，

现在如何将导航栏下拉到添加的照片中？

在红色圆圈中标记了三角形边缘。

我也尝试过this example，但在这里没有工作:'(

我的代码在这里给出：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
    <title>Bootstrap 101 Template</title>
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

  </head>
  <body>
<nav class="navbar navbar-default">
  <div class="container-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>
      <a class="navbar-brand" href="#">Brand</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">
        <li class="active"><a href="#">Link <span class="sr-only">(current)</span></a></li>
        <li><a href="#">Link</a></li>
      </ul>
      
      <ul class="nav navbar-nav navbar-right">
        <li><a href="#">Link</a></li>
        <li class="dropdown">
          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Dropdown <span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="#">Action</a></li>
            <li><a href="#">Another action</a></li>
            <li><a href="#">Something else here</a></li>
            <li role="separator" class="divider"></li>
            <li><a href="#">Separated link</a></li>
          </ul>
        </li>
      </ul>
    </div><!-- /.navbar-collapse -->
  </div><!-- /.container-fluid -->
</nav>
  </body>
</html>

【问题讨论】：

不鼓励在 Stack Overflow 上寻求一般帮助的问题。在发布问题之前，您应该研究过您的问题并尝试自己编写代码。如果您遇到特定的问题，请返回并在Minimal, Complete, and Verifiable example 中包含您尝试过的内容和相关代码的摘要。请阅读How much research effort is expected of Stack Overflow users
实际上我在创建那个三角形时陷入了困境（标记为红色圆圈）
您仍然需要在Minimal, Complete, and Verifiable example 中向我们展示您已经拥有的代码，以便我们提供帮助。

标签： html css twitter-bootstrap responsive-design

【解决方案1】：

现场演示：https://www.w3schools.com/bootstrap/tryit.asp?filename=trybs_dropdown-menu&stacked=h

下拉代码

<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
  <style>
  .dropdown-menu:before {
  position: absolute;
  top: -7px;
  left: 9px;
  display: inline-block;
  border-right: 7px solid transparent;
  border-bottom: 7px solid #ccc;
  border-left: 7px solid transparent;
  border-bottom-color: rgba(0, 0, 0, 0.2);
  content: '';
}

.dropdown-menu:after {
  position: absolute;
  top: -6px;
  left: 10px;
  display: inline-block;
  border-right: 6px solid transparent;
  border-bottom: 6px solid #ffffff;
  border-left: 6px solid transparent;
  content: '';
}
  </style>
</head>
<body>

<div class="container">
  <h2>Dropdowns</h2>
  <p>The .divider class is used to separate links inside the dropdown menu with a thin horizontal line:</p>
  <div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">Tutorials
    <span class="caret"></span></button>
    <ul class="dropdown-menu">
      <li><a href="#">HTML</a></li>
      <li><a href="#">CSS</a></li>
      <li><a href="#">JavaScript</a></li>
      <li class="divider"></li>
      <li><a href="#">About Us</a></li>
    </ul>
  </div>
</div>

</body>
</html>

【讨论】：

红圈处有三角边的那个
@Amin：为下拉菜单添加了 CSS，现在它与您正在查看的完全相同。