Bootstrap 4 在右侧显示下拉子菜单

Question

我在 Bootstrap 4 中创建了一个多级下拉菜单。我想在父下拉列表的右侧显示下拉子菜单。我已将菜单向右对齐，但这不是我想要的。如何在右侧显示下拉子菜单而不是右对齐？

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet" />


<nav class="navbar navbar-custom navbar-expand-md bg-dark navbar-dark">

  <button class="navbar-toggler" data-toggle="collapse" data-target="#collapse_target">
              <span class="navbar-toggler-icon"></span>                  
            </button>

  <div class="collapse navbar-collapse" id="collapse_target">

    <ul class="navbar-nav">
      <li class="nav-item dropdown">
        <a class="nav-link" data-toggle="dropdown" data-target="#dropdown_target" href="#">
                    DEPARTMENTS
                  </a>
        <ul class="dropdown-menu" aria-labelledby="dropdown_target">

          <li class="dropdown-item dropdown">
            <a data-toggle="dropdown" data-target="#auto_en" href="#">Automobile Engineering</a>
            <ul class="dropdown-menu dropdown-menu-right" aria-labelledby="auto_en">
              <li class="dropdown-item"><a href="#">HOD's Desk</a>
              </li>
              <li class="dropdown-item"><a href="#">About Us</a></li>
              <li class="dropdown-item"><a href="#">Faculty</a></li>
              <li class="dropdown-item"><a href="#">Events</a></li>
              <li class="dropdown-item"><a href="#">Class 
        Timetable</a></li>
              <li class="dropdown-item"><a href="#">Results</a></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </div>
</nav>

这里，汽车工程的子菜单是 -HOD的办公桌 -关于我们 -学院.... 我希望这个子菜单显示在包含汽车工程的父子菜单的右侧。

我使用了下拉菜单右引导类，但它使菜单向右对齐并且不显示在父菜单之外。

谢谢。

Answer 1

我想这就是你要找的https://codepen.io/svnt/pen/beEgre

HTML：

<div class="container">
    <div class="row">
        <h2>Multi level dropdown menu in Bootstrap</h2>
        <hr>
        <div class="dropdown">
            <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
              Dropdown
            </button>
            <ul class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
                <li class="dropdown-item"><a href="#">Some action</a></li>
                <li class="dropdown-item"><a href="#">Some other action</a></li>
                <li class="dropdown-divider"></li>
                <li class="dropdown-submenu">
                  <a  class="dropdown-item" tabindex="-1" href="#">Hover me for more options</a>
                  <ul class="dropdown-menu">
                    <li class="dropdown-item"><a tabindex="-1" href="#">Second level</a></li>
                    <li class="dropdown-submenu">
                      <a class="dropdown-item" href="#">Even More..</a>
                      <ul class="dropdown-menu">
                          <li class="dropdown-item"><a href="#">3rd level</a></li>
                            <li class="dropdown-submenu"><a class="dropdown-item" href="#">another level</a>
                            <ul class="dropdown-menu">
                                <li class="dropdown-item"><a href="#">4th level</a></li>
                                <li class="dropdown-item"><a href="#">4th level</a></li>
                                <li class="dropdown-item"><a href="#">4th level</a></li>
                            </ul>
                          </li>
                            <li class="dropdown-item"><a href="#">3rd level</a></li>
                      </ul>
                    </li>
                    <li class="dropdown-item"><a href="#">Second level</a></li>
                    <li class="dropdown-item"><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;
}

注意：代码不是我的。

Answer 2

将左侧添加到要更改其位置的下拉菜单中。如下图所示

.dropdown-menu.show.abc {
  left: 95%;
}

.dropdown-menu.show.abc {
  left: 95%;
  top: 20px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet" />


<nav class="navbar navbar-custom navbar-expand-md bg-dark navbar-dark">

  <button class="navbar-toggler" data-toggle="collapse" data-target="#collapse_target">
              <span class="navbar-toggler-icon"></span>                  
            </button>

  <div class="collapse navbar-collapse" id="collapse_target">

    <ul class="navbar-nav">
      <li class="nav-item dropdown">
        <a class="nav-link" data-toggle="dropdown" data-target="#dropdown_target" href="#">
                    DEPARTMENTS
                  </a>
        <ul class="dropdown-menu abc" aria-labelledby="dropdown_target">

          <li class="dropdown-item dropdown">
            <a data-toggle="dropdown" data-target="#auto_en" href="#">Automobile Engineering</a>
            <ul class="dropdown-menu dropdown-menu-right" aria-labelledby="auto_en">
              <li class="dropdown-item"><a href="#">HOD's Desk</a>
              </li>
              <li class="dropdown-item"><a href="#">About Us</a></li>
              <li class="dropdown-item"><a href="#">Faculty</a></li>
              <li class="dropdown-item"><a href="#">Events</a></li>
              <li class="dropdown-item"><a href="#">Class 
        Timetable</a></li>
              <li class="dropdown-item"><a href="#">Results</a></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </div>
</nav>

Answer 3

  .navbar-expand-md .navbar-nav .dropdown-menu {
        position: absolute;
        top: -7px;
        right: auto;
        left: 100%;
    }