Bootstrap 3多级菜单不显示二级项目

Question

我正在尝试使用 twitter Bootstrap 3 创建一个多级下拉菜单。我的 HTML 是：

<div class="navbar navbar-default navbar-fixed-top" role="navigation">
  <div class="container">
    <div class="navbar-header">
      <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
        <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="#">Project name</a>
    </div>
    <div class="navbar-collapse collapse">
      <ul class="nav navbar-nav">
        <li class="active"><a href="#">Home</a></li>
        <li class="dropdown">
          <a data-toggle="dropdown" class="dropdown-toggle" href="#">Dropdown <b class="caret"></b></a>
          <ul class="dropdown-menu">
            <li class="dropdown-submenu">
              <a href="#">More options</a>
              <ul class="dropdown-menu">
                <li><a href="#">Second level link</a></li>
                <li><a href="#">Second level link</a></li>
                <li><a href="#">Second level link</a></li>
                <li><a href="#">Second level link</a></li>
                <li><a href="#">Second level link</a></li>
              </ul>
            </li>
            <li><a href="#">Another action</a></li>
            <li><a href="#">Something else here</a></li>
            <li class="divider"></li>
            <li class="nav-header">Nav header</li>
            <li><a href="#">Separated link</a></li>
            <li><a href="#">One more separated link</a></li>
          </ul>
        </li>

      </ul>
      <ul class="nav navbar-nav navbar-right">
        <li><a href="../navbar/">Default</a></li>
        <li><a href="../navbar-static-top/">Static top</a></li>
        <li class="active"><a href="./">Fixed top</a></li>
      </ul>
    </div><!--/.nav-collapse -->
  </div>
</div>

从HERE 的答案中，我期待来自more options 的二级菜单。但它没有显示。怎么了？

Answer 1

试试下面的 CSS。

HTML：

    <div class="row">
            <a id="dLabel" role="button" data-toggle="dropdown" class="btn btn-primary" data-target="#" href="/page.html">
                Dropdown <span class="caret"></span>
        <h2>Multi level dropdown menu in Bootstrap 3</h2>
        <hr>
        <div class="dropdown">
            </a>
            <ul class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
              <li><a href="#">Some action</a></li>
              <li><a href="#">Some other action</a></li>
              <li class="divider"></li>
              <li class="dropdown-submenu">
                <a tabindex="-1" href="#">Hover me for more options</a>
                <ul class="dropdown-menu">
                  <li><a tabindex="-1" href="#">Second level</a></li>
                  <li class="dropdown-submenu">
                    <a href="#">Even More..</a>
                    <ul class="dropdown-menu">
                        <li><a href="#">3rd level</a></li>
                        <li><a href="#">3rd level</a></li>
                    </ul>
                  </li>
                  <li><a href="#">Second level</a></li>
                  <li><a href="#">Second level</a></li>
                </ul>
              </li>
            </ul>
        </div>
    </div>
</div>

CSS：

.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;
}