Question

我想制作一个水平导航栏，该菜单的顶部带有下拉菜单。问题在于，当我将导航栏置为粘性时，下拉菜单不再显示。

我使用以下CSS3来实现粘性效果。还有另一种方法可以达到相同的效果，尤其是使用CSS。

.topnav {
    overflow: hidden;
    background-color: #333;
    position: fixed;         /* This line adds stickyness */
    top: 0;                  /* along with this line here */
    width: 100%;
}

最小问题示例：

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

.topnav {
  overflow: hidden;
  background-color: #333;
  position: fixed;
  top: 0;
  width: 100%;
}

.topnav a {
  float: left;
  display: block;
  font-size: 16px;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

.dropdown {
  float: left;
  overflow: hidden;
}

.dropdown .dropbtn {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: inherit;
  font-family: inherit;
  margin: 0;
}

.topnav a:hover,
.dropdown:hover .dropbtn {
  background-color: red;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
}

.dropdown-content a {
  float: none;
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  text-align: left;
}

.dropdown-content a:hover {
  background-color: #ddd;
}

.dropdown:hover .dropdown-content {
  display: block;
}

.main {
  padding: 16px;
  margin-top: 30px;
  height: 1500px;
  /* Used in this example to enable scrolling */
}

<div class="topnav">
  <a href="#home">Home</a>
  <a href="#news">News</a>
  <div class="dropdown">
    <button class="dropbtn">Dropdown 
          <b>V</b>
        </button>
    <div class="dropdown-content">
      <a href="#">Link 1</a>
      <a href="#">Link 2</a>
      <a href="#">Link 3</a>
    </div>
  </div>
</div>
<div class="main">
  <h1>Fixed Top Menu</h1>
  <h2>Scroll this page to see the effect</h2>
  <h2>The navigation bar will stay at the top of the page while scrolling</h2>
  <h3>Dropdown Menu inside a Navigation Bar</h3>
  <p>Hover over the "Dropdown" link to see the dropdown menu.</p>
</div>

编辑：

感谢Saeed和dkobando。我只是网络文档之旅的开始。我一直在缓慢地将各种指南中的网站内容拼凑在一起。我对两个有用的迅速答案感到惊讶。您在这里的答复鼓励我继续前进。

Answer 1

这是因为下拉列表是绝对定位的，并且不会根据固定导航栏定位，而是根据最近的相对定位元素定位。可以使用固定位置的额外包装纸快速固定它。

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

.topnav {
  overflow: hidden;
  background-color: #333;
}

.fixed {
  position: fixed;
  top: 0;
  width: 100%;
}

.topnav a {
  float: left;
  display: block;
  font-size: 16px;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

.dropdown {
  float: left;
  overflow: hidden;
}

.dropdown .dropbtn {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: inherit;
  font-family: inherit;
  margin: 0;
}

.topnav a:hover,
.dropdown:hover .dropbtn {
  background-color: red;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
}

.dropdown-content a {
  float: none;
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  text-align: left;
}

.dropdown-content a:hover {
  background-color: #ddd;
}

.dropdown:hover .dropdown-content {
  display: block;
}

.main {
  padding: 16px;
  margin-top: 30px;
  height: 1500px;
  /* Used in this example to enable scrolling */
}

<div class="fixed">
  <div class="topnav">
    <a href="#home">Home</a>
    <a href="#news">News</a>
    <div class="dropdown">
      <button class="dropbtn">Dropdown 
            <b>V</b>
          </button>
      <div class="dropdown-content">
        <a href="#">Link 1</a>
        <a href="#">Link 2</a>
        <a href="#">Link 3</a>
      </div>
    </div>
  </div>
</div>
<div class="main">
  <h1>Fixed Top Menu</h1>
  <h2>Scroll this page to see the effect</h2>
  <h2>The navigation bar will stay at the top of the page while scrolling</h2>
  <h3>Dropdown Menu inside a Navigation Bar</h3>
  <p>Hover over the "Dropdown" link to see the dropdown menu.</p>
</div>

Answer 2

您可以在下面尝试此修复程序，我使用了display flex并消除了溢出：hidden;在您的.topnav类上。我希望这会有所帮助。

len

粘性topnav，但没有显示下拉菜单

2 个答案: