如何在 Bootstrap 4 中将下拉子菜单拉到左侧

Question

我正在使用 Bootstrap 4 并且我有如下所示的多级下拉菜单：

我想将子菜单拉到左边。因此，它目前显示的是相反的一面。我使用了多个 classes 例如 dropdown-menu-left, pull-left , dropleft 但没有改变拉动子菜单的方向。我还覆盖了下拉菜单 classe 但结果相同。

.dropdown-menu {
  left: auto;
  right: 0;
}

Boostrap 4 中将子菜单向左拉的正确 class 有什么建议吗？我在这里尝试了其他线程的解决方案，但它对我不起作用。非常感谢。

这是我的代码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Bootstrap 4 Navbar With Multilevel Dropdowns Example</title>
    <link href="https://www.jqueryscript.net/css/jquerysctipttop.css" rel="stylesheet" type="text/css">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootswatch/4.3.1/lumen/bootstrap.min.css">

    <style>
  .dropdown-submenu {
    position: relative;
  }
  
  .dropdown-submenu a::after {
    transform: rotate(-90deg);
    position: absolute;
    right: 6px;
    top: .8em;
  }
  
  .dropdown-submenu .dropdown-menu {
    top: 0;
    left: 100%;
    margin-left: .1rem;
    margin-right: .1rem;
  }

    </style>

</head>
<body>
    <nav class="navbar navbar-expand-lg">
        <div class="collapse navbar-collapse" id="navbarNavDropdown">
            <ul class="navbar-nav">
            <li class="nav-item active">
                <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 2</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 3</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 4</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 5</a>
            </li>
            <li class="nav-item dropdown">
                <a class="nav-link dropdown-toggle" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                Dropdown link
                </a>
                <ul class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
                    <li><a class="dropdown-item" href="#">Action</a></li>
                    <li><a class="dropdown-item" href="#">Another action</a></li>
                    <li class="dropdown-submenu">
                        <a class="dropdown-item dropdown-toggle" href="#">Submenu</a>
                        <ul class="dropdown-menu">
                        <li><a class="dropdown-item" href="#">Submenu action</a></li>
                        <li><a class="dropdown-item" href="#">Another submenu action</a></li>


                        <li class="dropdown-submenu">
                            <a class="dropdown-item dropdown-toggle" href="#">Subsubmenu</a>
                            <ul class="dropdown-menu">
                            <li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
                            <li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
                            </ul>
                        </li>
                        <li class="dropdown-submenu">
                            <a class="dropdown-item dropdown-toggle" href="#">Second subsubmenu</a>
                            <ul class="dropdown-menu">
                            <li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
                            <li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
                            </ul>
                        </li>
                        </ul>
                    </li>
                </ul>
            </li>
            </ul>
        </div>
    </nav>

<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>

<script>
    $('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
    if (!$(this).next().hasClass('show')) {
      $(this).parents('.dropdown-menu').first().find('.show').removeClass('show');
    }
    var $subMenu = $(this).next('.dropdown-menu');
    $subMenu.toggleClass('show');
  
  
    $(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
      $('.dropdown-submenu .show').removeClass('show');
    });
  
  
    return false;
  });
</script>

</body>
</html>

Answer 1

从您的源代码中复制，并添加了一些 class 样式，希望对您有所帮助。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Bootstrap 4 Navbar With Multilevel Dropdowns Example</title>
    <link href="https://www.jqueryscript.net/css/jquerysctipttop.css" rel="stylesheet" type="text/css">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootswatch/4.3.1/lumen/bootstrap.min.css">


    <script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
    <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>


    <style>
        .dropdown-submenu {
            position: relative;
        }

        .dropdown-submenu a::after {
            transform: rotate(-90deg);
            position: absolute;
            right: 6px;
            top: .8em;
        }

        .dropdown-submenu .dropdown-menu {
            top: 0;
            left: 100%;
            margin-left: .1rem;
            margin-right: .1rem;
        }

        .dropdown-submenu-left > .dropdown-menu{
            left: -100%;
            top: 0;
            margin: 0;
            padding: 0;
            right: 100%;
        }

        .first-sub-menu {
            width: 12rem;
            left: -122% !important;
        }

    </style>

</head>
<body>
<nav class="navbar navbar-expand-lg">
    <div class="collapse navbar-collapse" id="navbarNavDropdown">
        <ul class="navbar-nav">
            <li class="nav-item active">
                <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 2</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 3</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 4</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">Home 5</a>
            </li>
            <li class="nav-item dropdown">
                <a class="nav-link dropdown-toggle" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                    Dropdown link
                </a>
                <ul class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
                    <li><a class="dropdown-item" href="#">Action</a></li>
                    <li><a class="dropdown-item" href="#">Another action</a></li>
                    <li class="dropdown-submenu dropdown-submenu-left">
                        <a class="dropdown-item dropdown-toggle" href="#">Submenu</a>
                        <ul class="dropdown-menu first-sub-menu">
                            <li><a class="dropdown-item" href="#">Submenu action</a></li>
                            <li><a class="dropdown-item" href="#">Another submenu action</a></li>


                            <li class="dropdown-submenu dropdown-submenu-left">
                                <a class="dropdown-item dropdown-toggle" href="#">Subsubmenu</a>
                                <ul class="dropdown-menu">
                                    <li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
                                    <li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
                                </ul>
                            </li>
                            <li class="dropdown-submenu dropdown-submenu-left">
                                <a class="dropdown-item dropdown-toggle" href="#">Second subsubmenu</a>
                                <ul class="dropdown-menu">
                                    <li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
                                    <li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
                                </ul>
                            </li>
                        </ul>
                    </li>
                </ul>
            </li>
        </ul>
    </div>
</nav>

<script>
  $('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
    if (!$(this).next().hasClass('show')) {
      $(this).parents('.dropdown-menu').first().find('.show').removeClass('show');
    }
    var $subMenu = $(this).next('.dropdown-menu');
    $subMenu.toggleClass('show');


    $(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
      $('.dropdown-submenu .show').removeClass('show');
    });


    return false;
  });
</script>

</body>
</html>

Answer 2

您遇到的问题是因为您在 .dropdown-submenu .dropdown-menu 上设置了 left: 100%，所以当您添加 .dropleft class 时，它会被 left:100% 删除它，它应该可以正常工作；请看下面：https://jsfiddle.net/fdm6zer9/

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