javascript - 多级 Bootstrap 菜单只显示第一级

Question

我正在尝试使用 bootstrap 3 创建一个多级菜单，但无法让它工作，而且我对 bootstrap 的了解不足，无法找出原因

标记是

<div class="dropdown">
  <a role="button" data-toggle="dropdown" class="btn btn-primary" data-target="" href="">Y<span class="caret"></span></a>
  <ul class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
    <li class="dropdown-submenu">
        <a href="#" tabindex="-1">foo</a>         
        <ul class="dropdown-menu">
            <li>
              <a href="">bar</a>
            </li>
        </ul>
    </li>
  </ul>
</div>

css和js包含如下

<link href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">

<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>

我的期望是，当我打开第一个菜单(“Y”)时，我可以看到一个新的菜单项“foo”，打开它可以显示最后一个元素“bar”

该代码基于我找到的示例 here

Answer 1

似乎该片段中的 CSS 完成了有关多级下拉菜单的所有技巧。请参阅下面的工作片段:

.dropdown-submenu {
  position: relative;
}

.dropdown-submenu>.dropdown-menu {
  top: 0;
  left: 100%;
  margin-top: -6px;
  margin-left: -1px;
  -webkit-border-radius: 0 6px 6px 6px;
  -moz-border-radius: 0 6px 6px;
  border-radius: 0 6px 6px 6px;
}

.dropdown-submenu:hover>.dropdown-menu {
  display: block;
}

.dropdown-submenu>a:after {
  display: block;
  content: " ";
  float: right;
  width: 0;
  height: 0;
  border-color: transparent;
  border-style: solid;
  border-width: 5px 0 5px 5px;
  border-left-color: #ccc;
  margin-top: 5px;
  margin-right: -10px;
}

.dropdown-submenu:hover>a:after {
  border-left-color: #fff;
}

.dropdown-submenu.pull-left {
  float: none;
}

.dropdown-submenu.pull-left>.dropdown-menu {
  left: -100%;
  margin-left: 10px;
  -webkit-border-radius: 6px 0 6px 6px;
  -moz-border-radius: 6px 0 6px 6px;
  border-radius: 6px 0 6px 6px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<div class="dropdown">
  <a role="button" data-toggle="dropdown" class="btn btn-primary" data-target="" href="">Y<span class="caret"></span></a>
  <ul class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
    <li class="dropdown-submenu">
      <a href="#" tabindex="-1">foo</a>
      <ul class="dropdown-menu">
        <li>
          <a href="">bar</a>
        </li>
      </ul>
    </li>
  </ul>
</div>