折叠时看不到我的下拉按钮答案

【问题标题】：can't see my drop down button on collapse折叠时看不到我的下拉按钮
【发布时间】：2020-12-30 18:57:35
【问题描述】：

我是学习引导程序的新手，我正在努力使我的网站成为一个响应式导航栏。当我折叠页面时，我看不到典型的下拉汉堡图标，但我仍然可以单击页面中间的一个不可见的下拉按钮。任何有关如何更改导航下拉图标颜色的指导将不胜感激！

<link href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/js/bootstrap.bundle.min.js"></script>

<nav class="navbar navbar-custom navbar-static-top" role="navigation">
    <div class="container">
      <div class="navbar-header">
        <button type="button" class="navbar-toggle" data-toggle="collapse"
          data-target="#bs-example-navbar-collapse-1">
          <!-- <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span> -->
        </button>
      </div> 
      <div class="nav collapse navbar-collapse" id="bs-example-navbar-collapse-1">
        <ul class="nav navbar-nav">
          <li><a href="index.php">Home</a></li>
          <li><a href="#mailing">Mailing List</a></li>
          <li><a href="#pricing">Shop</a></li>
          <li><a href="#tour">Tour</a></li>
        </ul>
      </div>
    </div>
  </nav>

【问题讨论】：

给我的答案打个绿色勾号

标签： twitter-bootstrap nav

【解决方案1】：

类名应为 navbar-toggler，而不是 navbar-toggle。
在按钮中插入<span class="navbar-toggler-icon"></span>。
在您的导航栏中添加 navbar- 颜色和 bg- 颜色。

代码如下-

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css" integrity="sha384-TX8t27EcRE3e/ihU7zmQxVncDAy5uIKz4rEkgIXeMed4M0jlfIDPvg6uqKI2xXr2" crossorigin="anonymous">
<style>
</style>
</head>
<body>
  <nav class="navbar navbar-custom navbar-static-top navbar-light bg-light" role="navigation">
    <div class="container">
      <div class="navbar-header">
        <button type="button" class="navbar-toggler collapsed" data-toggle="collapse"
          data-target="#bs-example-navbar-collapse-1">
          <span class="navbar-toggler-icon"></span>
          <!-- <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span> -->
        </button>
      </div> 
      <div class="nav collapse navbar-collapse" id="bs-example-navbar-collapse-1">
        <ul class="nav navbar-nav">
          <li><a href="index.php">Home</a></li>
          <li><a href="#mailing">Mailing List</a></li>
          <li><a href="#pricing">Shop</a></li>
          <li><a href="#tour">Tour</a></li>
        </ul>
      </div>
    </div>
  </nav>
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ho+j7jyWK8fNQe+A12Hb8AhRq26LrZ/JpcUGGOn+Y7RsweNrtN/tE3MoK7ZeZDyx" crossorigin="anonymous"></script>

</body>
</html>

【讨论】：

【解决方案2】：

Bootstrap 4 中的navbar-toggler-icon（汉堡包）使用SVG background-image。

执行以下操作：将navbar-toggle 更改为navbar-toggler

将data-target="##bs-example-navbar-collapse-1" 更改为data-target="#navbarNav"

在按钮标签之间使用<span class="navbar-toggler-icon"></span>

将<div class="nav collapse navbar-collapse" id="bs-example-navbar-collapse-1"> 更改为 <div class="collapse navbar-collapse" id="navbarNav">

看到这个： https://jsfiddle.net/30s62mfb/3/

 <nav class="navbar navbar-light bg-light" role="navigation">
   
   
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

    
    <div class="collapse navbar-collapse" id="navbarNav">
        <ul class="nav navbar-nav">
          <li><a href="index.php">Home</a></li>
          <li><a href="#mailing">Mailing List</a></li>
          <li><a href="#pricing">Shop</a></li>
          <li><a href="#tour">Tour</a></li>
        </ul>
     
    </div> 
  </nav>

【讨论】：