Q1
如何在我的导航栏下拉菜单文本中心，当我尝试使用text-align:center;时，它会影响我不想要的主导航栏文本。
Q2 当用户将鼠标悬停在下拉菜单上的页面名称时，如何更改背景颜色的不透明度？
当用户将鼠标悬停在下拉菜单中的某个页面上时，白色背景会影响下拉菜单中的白色文本。另外，我想知道如何为这部分创建它自己的CSS，因为我认为如果你点击导航栏上的下拉菜单改变不透明度，主导航栏会受到影响当导航栏上文本的背景颜色变为白色时。
以下是我的代码。
HTML
<!DOCTYPE html>
<html>
<head>
<html lang="en">
<meta charset="UTF-8">
<title>Liam Docherty | London Web Developer & GFX designer</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" href="css/style.css">
</head>
<body>
<nav class="navbar navbar-default navbar-fixed-top">
<div class="container-fluid">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#"><img src="http://placehold.it/60x60" alt="Your Brand Name"></a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li><a href="#">Home</a>
</li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="true">About Me <span class="caret"></span></a>
<ul class="dropdown-menu">
<li><a href="#">Action</a>
</li>
<li><a href="#section3">Contact</a>
</li>
<li><a href="#">Something else here</a>
</li>
<li><a href="#">Separated link</a>
</li>
<li><a href="#">One more separated link</a>
</li>
</ul>
</li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Units <span class="caret"></span></a>
<ul class="dropdown-menu">
<li><a href="#">Action</a>
</li>
<li><a href="#">Another action</a>
</li>
<li><a href="#">Something else here</a>
</li>
<li><a href="#">Separated link</a>
</li>
<li><a href="#">One more separated link</a>
</li>
</ul>
</li>
<li><a href="#">Clients</a>
</li>
<li><a href="#contact-me">Contact Me</a>
</li>
</ul>
</div><!-- /.navbar-collapse -->
</div><!-- /.container-fluid -->
</nav>
<section class="section1">
<div class="hero"></div>
<a href= ".section2"><i class="fa fa-angle-down" style="font-size:100px;"></i></a>
</section>
<section class="section2">
<a href = ".section2"> <i class="fa fa-angle-down" style="font-size:100px;"></i></a>
</section>
<section class="section3" id="section3">
<a href = "#bs-example-navbar-collapse-1"> <i class="fa fa-angle-up" style="font-size:100px;"></i></a>
</section>
<script src="https://code.jquery.com/jquery-3.1.1.js" integrity="sha256-16cdPddA6VdVInumRGo6IbivbERE8p7CQR3HzTBuELA=" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</body>
<footer>
<div class="page">
<h1 class="footer">Copyright © 2017 Liam Docherty's Site. All rights reserved.</h1>
</div>
</footer>
</html>
CSS
<style>
body {
margin: 0;
padding: 0;
}
.navbar.navbar-default {
background-color: #4D5061;
height: 10vh;
z-index: 100;
}
.navbar.navbar-default ul {
list-style-type: none;
text-align: right;
}
.navbar.navbar-default ul li {
display: inline-block;
}
.dropdown .dropdown-menu {
background-color: #4D5061;
}
.dropdown .dropdown-menu a {
color: white;
}
.navbar.navbar-default ul li a {
display: inline-block;
padding: 3.5vh 8px 4px;
color: white;
text-decoration: none;
font-size: 14pt;
font-family: 'Roboto', sans-serif;
}
.navbar.navbar-default ul li:after {
content: '';
position: absolute;
right: 50%;
bottom: 0;
left: 50%;
height: 3px;
background-color: #FFFFFF;
border-radius: 9px;
transition: all .2s;
}
.navbar.navbar-default ul li a:hover {
color: white;
}
.nav.navbar-nav,
.nav.navbar-nav>li {
float: none;
}
.navbar.navbar-default ul li:hover:after {
right: 0;
left: 0;
}
a:hover {
color: red;
text-decoration: none;
}
#logo {
padding-top: 2vh;
padding-left: 20px;
float: left;
}
section {
position: relative;
height: 95vh;
}
.section1 {
height: 100vh;
text-align: center;
color: white;
background-image: url("https://static.pexels.com/photos/48727/pexels-photo-48727.jpeg");
background-attachment: fixed;
}
.section2 {
//height: 95vh;
background-color: #A59E8C;
text-align: center;
color: white;
}
.section3 {
//height: 95vh;
background-color: #A59E8C;
text-align: center;
color: white;
}
.fa-angle-down {
color: #4D5061;
position: absolute;
bottom: 0px;
}
.fa-angle-up {
color: #4D5061;
position: absolute;
bottom: 0px;
}
.footer {
height: 5vh;
background-color: #4D5061;
text-align: center;
padding:0;
right:0;
bottom:0;
left:0:
}
h1{
font-size: 14pt;
margin:0;
color: white;
font-family: 'Roboto', sans-serif;
}
.navbar.navbar-default ul.dropdown-menu li,
.navbar.navbar-default ul.dropdown-menu li a {
position: relative;
display: block;
}
</style>
答案 0 :(得分：0)
要设置下拉列表的样式而不设置主导航样式，请将其下拉列表自己的类名称。然后就可以了
.navbar .navbar-default .customClassName{
...styles for just the drop down
}
答案 1 :(得分：0)
由于您的填充，您的放置菜单项文本似乎偏离中心。你的填充（3.5vh 8px 4px）给出了不同的顶部和底部填充。 Vh取屏幕尺寸的百分比，而4px是静态量。如果你在顶部和底部使用相同的填充，它应该工作（填充：4px 8px）像Hadas所说，考虑使用类来避免破坏你网站的其他部分。
答案 2 :(得分：0)
.nav ul.dropdown-menu li a:hover {
background-color: rgba(238, 238, 238, 0.75);
}
要仅为背景颜色设置不透明度，您必须根据RGBA在悬停时编写背景颜色属性。使用http://hex2rgba.devoth.com/之类的工具将当前十六进制转换为具有不透明度级别的RGBA，并将background-color属性添加到元素的：悬停状态。
直接设置不透明度属性也会改变文本和内容的不透明度。