如何使下拉菜单超出父列的宽度？

Question

我有一个下拉菜单，里面有 3 个主要 "categories"，每个 "category" 都有几个复选框（这用于过滤搜索）。这是我的代码示例：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

<div class="col-3 dropdown">
    <button type="button" class="btn dropdown-toggle" data-toggle="dropdown">Button</button>
    <div class="dropdown-menu">
        <div class="dropdown-item">
            <div class="row">
                <div class="col">
                    <h6>Category 1:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 2:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 3:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
            </div>
        </div>
    </div>
</div>

您可能已经注意到，下拉菜单 div 也是一个 col-3。基本上，我希望下拉菜单比 col-3 占据更多的水平 space（就像 text-nowrap 在 div 中处理简单文本一样）。
这是一个我希望它看起来像的示例：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

<div class="dropdown">
    <button type="button" class="btn dropdown-toggle" data-toggle="dropdown">Button</button>
    <div class="dropdown-menu">
        <div class="dropdown-item">
            <div class="row">
                <div class="col">
                    <h6>Category 1:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 2:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 3:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
            </div>
        </div>
    </div>
</div>

Answer 1

默认情况下，Bootstrap 将 position:relative 应用于 .dropdown class。如果您希望下拉列表的子元素超出下拉列表，则在下拉列表中添加一个 class 以覆盖 position:relative。这里我添加了 .extended class.

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<style>
     .extended {
         position: initial !important;
     }
</style>
<div class="col-3 dropdown extended">
    <button type="button" class="btn dropdown-toggle" data-toggle="dropdown">Button</button>
    <div class="dropdown-menu">
        <div class="dropdown-item">
            <div class="row">
                <div class="col">
                    <h6>Category 1:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 2:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
                <div class="col">
                    <h6>Category 3:</h6>
                    <ul class="list-group">
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option1</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option2</a></li>
                        <li class="list-group-item"><a href="#"><input type="checkbox"> Option3</a></li>
                    </ul>
                </div>
            </div>
        </div>
    </div>
</div>

如何使下拉菜单超出父列的宽度？

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