使用CSS将子菜单添加到预先存在的导航中

Question

我有一个预先存在的响应式菜单，但我需要为每个菜单选项添加一个子导航。我怎么能用CSS做到这一点？

我认为重要的代码在主要导航部分。

提前感谢所有能帮助我了解子菜单如何工作的人。

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/** 
/* 06. =header styles
/* =================================================================== */

html,
body {
	height: 100%;
}

body {
	background: #0F1215;
	font: 16px/30px "merriweather-regular", serif;
	font-weight: normal;
	color: #575859;
}


header {
	height: 66px;
	width: 100%;
	position: fixed;
	left: 0;
	top: 0;
	z-index: 600;
	-moz-transition: all 0.5s ease-in-out;
	-o-transition: all 0.5s ease-in-out;
	-webkit-transition: all 0.5s ease-in-out;
	-ms-transition: all 0.5s ease-in-out;
	transition: all 0.5s ease-in-out;  

	
}
header.opaque {
	background: black;
	border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

/* header logo */
header .logo {
	background: #fdc501;
	float: left;
	width: auto;
	margin-left: 15px;
	margin-right: 30px;
	z-index: 600;    
	
	/* add position relative since z-index only applies to  
	elements that have been given an explicit position */
	position: relative;
}

header .logo a {
	display: block;
	margin: 0;
	padding: 0;
	border: none;
	font: 0/0 a;
	text-shadow: none;
	color: transparent;
	width: 114px;
	height: 66px;
	background: url("../images/logoK@2x.png") no-repeat center;
	background-size: 61px 14px;
}

/* header social */
header .header-social {
	font-size: 20px;
	font-weight: normal;
	line-height: 66px;
	margin-top: 0;
	margin-left: 30px;
	padding-left: 36px;
	border-left: 1px solid rgba(150, 150, 150, 0.2);
	float: left;
	position: relative;
	top: -1px;
}

header .header-social li {
	display: inline-block;
	margin-right: 15px;
}

header .header-social li a {
	color: #FFFFFF;
}

header .header-social li a:hover {
	color: #fdc501;
}

/* media queries:  
/* header/header components */
@media only screen and (max-width:880px) {
	header .header-social {
		display: none;
	}

}

@media only screen and (max-width:768px) {
	header {
		background: black;
		border-bottom: 1px solid rgba(255, 255, 255, 0.1);
	}

	header .row {
		width: 100%;
	}

	header .logo {
		margin-left: -30px;
	}

}

/* primary navigation
--------------------------------------------------------------------- */
#nav-wrap,
#nav-wrap ul,
#nav-wrap li,
#nav-wrap a {
	margin: 0;
	padding: 0;
}

/* nav-wrap */
#nav-wrap {
	font: 13px "raleway-heavy", sans-serif;
	text-transform: uppercase;
	letter-spacing: 1.5px;
	float: left;  
}

/* hide toggle button */
#nav-wrap > a {
	display: none;
}

ul#nav {
	min-height: 66px;
	display: inline-block;
	width: auto;  

	/* left align the menu */
	text-align: left;
}

ul#nav li {
	position: relative;
	list-style: none;
	display: inline-block;
	height: 66px;    
}

/* Links */
ul#nav li a {

	/* 14px padding top + 14px padding bottom + 38px line-height = 66px */
	display: block;
	padding: 14px 12px;
	line-height: 38px;
	text-decoration: none;
	text-align: left;
	color: #FFFFFF;
	position: relative;
	-moz-transition: color 0.2s ease-in-out;
	-o-transition: color 0.2s ease-in-out;
	-webkit-transition: color 0.2s ease-in-out;
	-ms-transition: color 0.2s ease-in-out;
	transition: color 0.2s ease-in-out;
}

ul#nav li a:hover {
	color: #fdc501;
}

ul#nav li a:active {
	background-color: transparent !important;
}

ul#nav li.current a {
	color: #fdc501;
}

ul#nav li.current a:after {
	position: absolute;
	left: 50%;
	bottom: 0;
	width: 40px;
	height: 2px;
	margin-left: -23px;
	background-color: white;
	content: '\0020';
	display: block;
	-moz-transition: all 0.3s ease-in-out;
	-o-transition: all 0.3s ease-in-out;
	-webkit-transition: all 0.3s ease-in-out;
	-ms-transition: all 0.3s ease-in-out;
	transition: all 0.3s ease-in-out;
}

/* mobile navigation 
--------------------------------------------------------------------- */
@media only screen and (max-width:768px) {
	#nav-wrap {
		z-index: 700;
		display: block;
		width: 100%;
		float: none;
		position: absolute;
		top: 0;
		right: 0;
	}

	/* mobile-btn and toggle-btn */
	#nav-wrap > a {
		border: none;
		color: #FFFFFF;
		height: 40px;
		min-width: 40px;
		font-size: 12px;
		text-align: left;
		float: right;
		display: block;
		padding: 0;
		position: relative;
		top: 13px;
		right: 20px;
	}

	#nav-wrap > a:hover .menu-icon {
		background: #FFFFFF;
	}

	#nav-wrap .menu-icon {
		display: inline-block;
		width: 24px;
		height: 3px;
		margin-top: -3px;
		position: absolute;
		right: 8px;
		top: 50%;
		bottom: auto;
		left: auto;
		background: #fdc501;
		-moz-transition: all 0.3s ease-in-out;
		-o-transition: all 0.3s ease-in-out;
		-webkit-transition: all 0.3s ease-in-out;
		-ms-transition: all 0.3s ease-in-out;
		transition: all 0.3s ease-in-out;
		font: 0/0 a;
		text-shadow: none;
		color: transparent;
	}

	#nav-wrap .menu-icon:before,
	#nav-wrap .menu-icon:after {
		content: '';
		width: 100%;
		height: 100%;
		position: absolute;
		background-color: inherit;
		left: 0;
	}

	#nav-wrap .menu-icon:before {
		bottom: 8px;
	}

	#nav-wrap .menu-icon:after {
		top: 8px;
	}

	/* dropdown nav */
	#nav-wrap ul#nav {
		background: #1c212a;
		padding: 54px 45px 60px 45px;
		margin: 0;
		height: auto;
		display: none;
		clear: both;
		width: 100%;
		float: none;
		position: absolute;
		top: 66px;
		right: 0;
	}

	#nav-wrap ul#nav > li {
		display: block;
		float: none;
		height: auto;
		text-align: left;
		border-bottom: 1px dotted rgba(200, 200, 200, 0.1);
		padding: 6px 0;
	}

	#nav-wrap ul#nav > li:first-child {
		border-top: 1px dotted rgba(200, 200, 200, 0.1);
	}

	#nav-wrap ul#nav li a {
		display: block;
		width: auto;
		padding: 0;
		color: #cacbcb;
		padding: 12px 0;
		line-height: 16px;
		border: none;
	}

	#nav-wrap ul#nav li a:hover {
		color: #FFFFFF;
	}

	#nav-wrap ul#nav li.current > a {
		background: none;
		color: #fdc501;
	}

	#nav-wrap ul#nav li.current > a:after {
		display: none;
	}

	#nav-wrap a.mobile-btn {
		display: none;
	}

	.js #nav-wrap a#toggle-btn {
		display: block;
	}

	/* if js is disabled */
	.no-js #nav-wrap:not(:target) > a:first-of-type,
	.no-js #nav-wrap:target > a:last-of-type {
		display: block;
	}

	.no-js #nav-wrap:target ul#nav {
		display: block;
	}

}

/* make sure the menu is visible on larger screens
--------------------------------------------------------------------- */
@media only screen and (min-width:769px) {
	#nav-wrap ul#nav {
		display: block !important;
	}

}

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 <header id="main-header">

   	<div class="row">

	      <div class="logo">
	         <a href="index.html">SAT | Aloia Evelina</a>
	      </div>

	      <nav id="nav-wrap">         
	         
	         <a class="mobile-btn" href="#nav-wrap" title="Show navigation">
	         	<span class="menu-icon">Menu</span>
	         </a>
         	<a class="mobile-btn" href="#" title="Hide navigation">
         		<span class="menu-icon">Menu</span>
         	</a>            

	         <ul id="nav" class="nav">
	            <li><a class="smoothscroll" href="#hero">Home.</a></li>
		         <li class="current"><a class="smoothscroll" href="#portfolio">Works.</a></li>
	            <li><a class="smoothscroll" href="#services">Services.</a></li>
	            <li><a class="smoothscroll" href="#about">About.</a></li>
	            <li><a class="smoothscroll" href="#contact">Contact.</a></li>
	         </ul> <!-- end #nav -->

	      </nav> <!-- end #nav-wrap -->

	      <ul class="header-social">
	        	<li><a href="#"><i class="fa fa-facebook"></i></a></li>
	        	<li><a href="#"><i class="fa fa-twitter"></i></a></li>
	        	<li><a href="#"><i class="fa fa-google-plus"></i></a></li>
	      </ul>      

	   </div>

   </header> <!-- end header -->

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Answer 1

<ul id="nav" class="nav">
<li><a class="smoothscroll" href="#hero">Home.</a>
    <ul>
        <li><a href="#">#item1</a></li>
        <li><a href="#">#item1</a></li>
    </ul>
</li>
<li class="current"><a class="smoothscroll" href="#portfolio">Works.</a>
    <ul>
        <li><a href="#">#item1</a></li>
        <li><a href="#">#item1</a></li>
    </ul>
</li>
<li><a class="smoothscroll" href="#services">Services.</a>
    <ul>
        <li><a href="#">#item1</a></li>
        <li><a href="#">#item1</a></li>
    </ul>
</li>
<li><a class="smoothscroll" href="#about">About.</a>
    <ul>
        <li><a href="#">#item1</a></li>
        <li><a href="#">#item1</a></li>
    </ul>
</li>
<li><a class="smoothscroll" href="#contact">Contact.</a>
    <ul>
        <li><a href="#">#item1</a></li>
        <li><a href="#">#item1</a></li>
    </ul>
</li> </ul>

在您的html文件中，您的代码应该是这样的。

然后，有关如何设置代码样式的更多详细信息，请访问网站https://css-tricks.com/targetting-menu-elements-submenus-navigation-bar/

它提供了一些技巧，您可以在其中设置菜单样式以及html文件的外观。我发现它非常有帮助。