使用下拉菜单创建粘性导航栏 HTML

Question

我正在创建一个 HTML 网页，其中包含一个带下拉菜单的粘性导航栏。但是，当我创建一个时，下拉菜单在粘性导航栏中不起作用，反之亦然。下面是两个代码的结果截图。

*image with dropdown menu but without sticky navbar

*image with sticky navbar but without dropdown menu

下面是“带有下拉菜单但没有粘性导航栏的图像”的代码

    <!DOCTYPE html>
    <html>
    <head>
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-    awesome/4.7.0/css/font-awesome.min.css">
    <style>
    body {margin:0;font-family:Arial}

   .topnav {
    overflow: hidden;
    background-color: #333;
  }

  .topnav a {
    list-style-type: none;
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 17px;
    position: sticky;
  }



  .active {
    background-color: #04AA6D;
    color: white;
  }

  .topnav .icon {
    display: none;
  }

  .dropdown {
    float: left;
    overflow: hidden;
  }

  .dropdown .dropbtn {
    font-size: 17px;    
    border: none;
    outline: none;
    color: white;
    padding: 14px 16px;
    background-color: inherit;
    font-family: inherit;
    margin: 0;
  }

  .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;
  }

  .topnav a:hover, .dropdown:hover .dropbtn {
    background-color: #555;
    color: white;
  }

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

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

  @media screen and (max-width: 600px) {
    .topnav a:not(:first-child), .dropdown .dropbtn {
    display: none;
  }
    .topnav a.icon {
      float: right;
      display: block;
    }
  }

  @media screen and (max-width: 600px) {
    .topnav.responsive {position: relative;}
    .topnav.responsive .icon {
      position: absolute;
      right: 0;
      top: 0;
    }
    .topnav.responsive a {
      float: none;
      display: block;
      text-align: left;
    }
    .topnav.responsive .dropdown {float: none;}
    .topnav.responsive .dropdown-content {position: relative;}
    .topnav.responsive .dropdown .dropbtn {
      display: block;
      width: 100%;
      text-align: left;
    }
  }
  </style>
  </head>
  <body>
        <div class="header">
        <h2>Scroll Down</h2>
    <p>Scroll down to see the sticky effect.</p>
  </div>

  <div class="topnav" id="myTopnav">
    <a href="#home" class="active">Home</a>
    <a href="#news">News</a>
    <a href="#contact">Contact</a>
    <div class="dropdown">
      <button class="dropbtn">Dropdown 
        <i class="fa fa-caret-down"></i>
      </button>
      <div class="dropdown-content">
        <a href="#">Link 1</a>
        <a href="#">Link 2</a>
        <a href="#">Link 3</a>
      </div>
    </div> 
    <a href="#about">About</a>
    <a href="javascript:void(0);" style="font-size:15px;" class="icon"     onclick="myFunction()">&#9776;</a>
  </div>

  <div style="padding-left:16px">
    <h2>Responsive Topnav with Dropdown</h2>
    <p>Resize the browser window to see how it works.</p>
    <p>Hover over the dropdown button to open the dropdown menu.</p>
  </div>

  <h3>Sticky Navigation Bar Example</h3>
  <p>The navbar will <strong>stick</strong> to the top when you reach its scroll position.</p>
  <p><strong>Note:</strong> Internet Explorer do not support sticky positioning and Safari         requires a -webkit- prefix.</p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>
  <p>Some text to enable scrolling. </p>


  <script>
  function myFunction() {
    var x = document.getElementById("myTopnav");
    if (x.className === "topnav") {
      x.className += " responsive";
    } else {
      x.className = "topnav";
    }
  }
  </script>

  </body>
  </html>

下面是“带有粘性导航栏但没有下拉菜单的图像”的代码

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-    awesome/4.7.0/css/font-awesome.min.css">
<style>


body {
  font-size: 20px;
}
body {margin:0;}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
  position: -webkit-sticky; /* Safari */
  position: sticky;
  top: 0;
}

li {
  float: left;
}

li a {
  display: block;
  color: white;
  text-align: center;
  padding: 16px 20px;
  text-decoration: none;
}

li a:hover {
  background-color: #111;
}
    
/*======================================================================*/

body {
  background-color:white;
}
ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #38444d;
}

li {
  float: left;
}

li a, .dropbtn {
  display: inline-block;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

li a:hover, .dropdown:hover .dropbtn {
  background-color: red;
}

li.dropdown {
  display: inline-block;
}

.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 {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  text-align: left;
}

.dropdown-content a:hover {background-color: #f1f1f1;}

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


footer {
  text-align: center;
  padding: 3px;
  background-color: DarkSalmon;
  color: white;
}

</style>
</head>
<body>

<div class="header">
  <h2>Scroll Down</h2>
  <p>Scroll down to see the sticky effect.</p>
</div>

<ul>
  <li><a href="#home">Home</a></li>
    <li><a href="#news">News</a></li>
    <li class="dropdown">
      <a href="javascript:void(1)" class="dropbtn">Dropdown</a>
      <div class="dropdown-content">
        <a href="#">Link 1</a>
        <a href="#">Link 2</a>
        <a href="#">Link 3</a>
      </div>
    </li>
</ul>

<h3>Sticky Navigation Bar Example</h3>
<p>The navbar will <strong>stick</strong> to the top when you reach its scroll position.</p>
<p><strong>Note:</strong> Internet Explorer do not support sticky positioning and Safari requires a -webkit- prefix.</p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>
<p>Some text to enable scrolling. </p>


<footer>
  <p>Author: Hege Refsnes<br>
  <a href="mailto:hege@example.com">hege@example.com</a></p>
</footer>


</body>
</html>

我需要一些帮助，因为我是 html 和 css 的新手。

Answer 1

在第一个代码中，从导航栏中删除溢出属性，并像这样向其中添加一个min-height，

.topnav {
      /* overflow: hidden; */
      background-color: #333;
      position: sticky;
      top: 0;
      min-height: 45px;
    }

由于您在导航项中使用了浮动属性，这可能会造成问题

工作代码Code

Answer 2

我已更正您的代码，因为溢出隐藏的下拉菜单不可见，请查看此代码。如果您愿意，我可以在此处粘贴完整代码。希望对您有所帮助。

您的第一个代码解决方案

 .topnav {
            background-color: #333;
            position: sticky;
            top: 0;
        }
        @media screen and (min-width:768px){
            .topnav {
            display: flex;
        }  
        }
@media screen and (max-width: 767.98px){
    .topnav {
            overflow: hidden;
        }  
}

你的第二个代码解决方案

ul {
    display: flex;
  list-style-type: none;
  margin: 0;
  padding: 0;
  /* overflow: hidden; */
  background-color: #333;
  position: -webkit-sticky; /* Safari */
  position: sticky;
  top: 0;
}
ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  /* overflow: hidden; */
  background-color: #38444d;
}

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