列表元素内的下拉菜单扩展了列表大小，并且难以访问

Question

我有一个包含列表的div。此列表包含多个下拉元素。选择列表底部的下拉元素后，列表的大小将扩展以适应这些新元素。但是，除非用户向下滚动以单击它们，否则这些元素也会被隐藏。首选的解决方案是让下拉元素显示在列表中所有其他元素的上方。但是，无论我尝试哪种组合，尝试通过 z 索引和绝对/相对定位来做到这一点似乎都不起作用。我缺少的这个问题有什么解决方法吗？

注意：全屏时最佳模拟。

/*CSS borrowed from https://www.w3schools.com/howto/tryit.asp?filename=tryhow_css_js_dropdown_hover*/
.dropbtn {
background-color: #4CAF50;
color: white;
padding: 16px;
font-size: 16px;
border: none;
}

.dropdown {
position: relative;
display: inline-block;
}

.dropdown-content {
display: none;
position: absolute;
background-color: #f1f1f1;
min-width: 160px;
z-index: 100;
}

.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
}

.dropdown-content a:hover {background-color: #ddd}

.dropdown:hover .dropdown-content {
display: block;
}

.dropdown:hover .dropbtn {
background-color: #3e8e41;
}

/* Other random CSS */

.background {
height : 500px;
width  : 800px;
background-color: #d47500
}

.list-holder{
height : 300px;
overflow-y : auto;
background-color: #b2815b
}

<div class="background">

<div class="list-holder">

<ul>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<!-- Problem -->
<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<!-- Problem -->
<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<!-- Problem -->
<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

</ul>


</div>

</div>

我正在考虑的一个解决方案是使用 javascript 在所有其他div 之上生成类似的下拉菜单。 不幸的是，我不确定如何开始这样做。如果有人对如何做有任何想法，请告诉我。

编辑：

• 对于此实现，固定列表大小是必需的。

Answer 1

如果您在导航的父容器上设置了overflow-y: auto和显式高度，则absolute定位和z-indexs 将无济于事。如果您删除它们，它的行为会按照您想要的方式进行，例如：

.dropbtn {
background-color: #4CAF50;
color: white;
padding: 16px;
font-size: 16px;
border: none;
}
.dropdown {
position: relative;
display: inline-block;
}
.dropdown-content {
display: none;
position: absolute;
background-color: #f1f1f1;
min-width: 160px;
z-index: 100;
}
.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
}
.dropdown-content a:hover {background-color: #ddd}
.dropdown:hover .dropdown-content {
display: block;
}
.dropdown:hover .dropbtn {
background-color: #3e8e41;
}
.background {
height: 500px;
background-color: #d47500
}
.list-holder{
position: relative;
background-color: #b2815b
}

<div class="background">
<div class="list-holder">

<ul>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

<li>
<div class="dropdown">
<button class="dropbtn">Dropdown</button>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</div>
</li>

</ul>

</div>
</div>