Pure CSS to achieve multi-level navigation linkage (with pictures and text examples)-CSS Tutorial-php.cn

Preface

Navigation bars have been done before...but they were all very simple first-level navigation bars or Secondary navigation bar implemented with JQ. But the things displayed on the page should still be implemented by CSS, and JavaScript should be more responsible for the actions. [Recommended: css video tutorial]

Basics

The first is the secondary navigation bar, for example:

Pure CSS to achieve multi-level navigation linkage (with pictures and text examples) ##Before I’ve never understood it… Actually, this kind of thing is very simple to put it bluntly….

The main points are:

1. What should the structure of the entire navigation look like

2. Without JS , how to make the second-level navigation appear when the mouse moves to the first-level navigation.

3. Positioning of the secondary navigation bar.

Analysis:

1. The more mainstream approach should be to use the ul tag. Each ul tag is a navigation level, the li inside is a sub-project, and the li contains a tag and ul tag. The a tag is used to click to jump, ul is the navigation bar of the next level, and so on...

2. Move the mouse to the first-level navigation bar to display the second-level navigation bar. The first reaction is the hover pseudo-class. According to previous understanding, hover is used to control its own changes. How can we control the sub-elements? What about style? In fact, this is enough:

    #nav li:hover ul{
            display: block;
        }

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When the li of the first-level navigation is covered by the mouse, the ul in the child element is displayed.

......

It turns out it can still be like this, but my previous understanding was wrong. I originally thought

li:hover was just a state, but in fact it is also an element.

This code treats the entire li:hover as an element, but this element is special. It is defined as "when the mouse covers the li element of the li element", it is also an element. In this way, when the mouse covers the li element element, the element pointed by the mouse is li:hover. At this time, the ul element under li:hover is controlled to be displayed, and the purpose is achieved.

I'm so witty.

3. So how to make the second-level ul appear just below the first-level li?

1) The second-level ul is wrapped in the first-level li. In fact, just use relative positioning, and it is not just directly below. At this time, it has been separated from the document flow, and you want to position it wherever you want. It will be all right.

2) What if for some reason, or you are obsessive-compulsive, you don’t want to get out of the document flow?

In fact, just "squeeze" it down. There are a tags and ul tags in li. When the a tag is large enough and occupies all the positions, ul will naturally be squeezed underneath. .

Code above:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>吃货的导航栏</title>
    </head>
    <style type="text/css">
        *{
            margin:0px;
            padding:0px;
        }
        #nav{
            width: 600px;
            height: 40px;
            background: gray;
            margin: 0 auto;
        }
        #nav li{
            line-height: 40px;
            float: left;
            list-style: none;
            height: 40px;
            position: relative;
        }
        #nav a{
            padding: 0 20px;
            color: black;
            display: block;
            text-decoration: none;
            height: 40px;
        }
        #nav a:hover{
            background: #058;
            color:white;
        }
        #nav li ul{

            display: none;
            position: absolute;
            top: 40px;
            left:0px;
        }
        #nav li ul li{
            float: none;
            margin: 2px;
            width:100px;
            text-align: center;
        }
        #nav li ul li a{
            background: #ccc;
        }
        #nav li ul li a:hover{
            background: deeppink;
        }
        #nav li:hover ul{
            display: block;
        }
    </style>
    <body>
        <ul id="nav">
            <li><a href="#">首页</a></li>
            <li><a href="#">肉类</a>
                <ul>
                    <li><a href="#">牛肉</a></li>
                    <li><a href="#">猪肉</a></li>
                    <li><a href="#">鸡肉</a></li>
                </ul>
            </li>
            <li><a href="#">水果</a>
                <ul>
                    <li><a href="#">西瓜</a></li>
                    <li><a href="#">香蕉</a></li>
                    <li><a href="#">苹果</a></li>
                </ul>
            </li>
            <li><a href="#">零食</a></li>
            <li><a href="#">蔬菜</a>
                <ul>
                    <li><a href="#">白菜</a></li>
                </ul>
            </li>
        </ul>
    </body>
</html>

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This is the most basic secondary navigation bar, but with this foundation, you have a basis for making multi-level navigation bars and various effects.

Multi-level navigation bar

Based on the above principles, you can easily create a multi-level navigation bar. Take the three-level one as an example to learn to make a good-looking one.

Pure CSS to achieve multi-level navigation linkage (with pictures and text examples) It is also a structure of li embedded with ul, using relative positioning and a little transition effect, and using small triangles made by border. The principle is to change the color of other borders to transparent. .

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>吃货的动画导航栏</title>
    </head>
    <style type="text/css">
        *{
            margin: 0px;
            padding: 0px;
        }
        .top-nav{
            width: 960px;
            margin: 0 auto;
            list-style: none;
            background-image: linear-gradient(#444, #111);
            border-radius: 6px;
            box-shadow: 0 1px 10px #777;
        }
        .top-nav:before,.top-nav:after{
            content: "";
            display: table;
        }
        .top-nav:after{
            clear: both;
        }
        .top-nav>li{
            float: left;
            border-right: 1px solid saddlebrown;
            position: relative;
            line-height: 40px;
        }
        .top-nav li{
            position: relative;
        }
        .top-nav>li a{
            font: "微软雅黑" 12px;
            text-decoration: none;
            color: goldenrod;
            padding: 12px 30px;
        }
        .top-nav>li a:hover{
            color:#fafafa;
        }
        .top-nav li ul{
            position: absolute;
            border-radius: 6px;
            z-index: 1;
            top: 40px;
            left: 0px;
            list-style: none;
            background-image: linear-gradient(#444, #111);
            box-shadow: 0 -1 0 rgba(255,255,255,0.3);
            visibility: hidden; /*这里只能用hidden 不能display*/
            opacity: 0;
            margin: 20px 0 0 0;
            transition: all .2s ease-in-out;
        }
        .top-nav ul ul{
            margin-left: 20px;
            margin-top: 20px;
        }
        .top-nav ul li:hover>ul{
            margin-left: 0px;
        }

        .top-nav li:hover>ul{
            opacity: 1;
            visibility: visible;
            margin: 0;
        }
        .top-nav ul a{
            padding: 15px;
            width: 70px;
            display: block;
        }
        .top-nav ul a:hover{
            background-image: linear-gradient(#04acec, #0186ba);
        }
        .top-nav ul li:first-child>a{
            border-radius: 6px 6px 0 0;
        }/*第一个跟最后一个a标签设置圆角*/
        .top-nav ul li:last-child>a{
            border-radius: 0 0 6px 6px;
        }
        .top-nav ul li{
            box-shadow: 0 1px 0 #111, 0 2px 0 #666;
        }/*两个阴影叠加产生间隔*/
        .top-nav ul li:first-child>a:before{
            content: "";/*这句不可少，少了没效果*/
            display: block;
            width: 0;
            border-left: 6px solid transparent;
            border-right: 6px solid transparent;
            border-bottom: 6px solid #444;
            position: absolute;
            top: -6px;
            left: 40px;
        }
        .top-nav ul li:first-child>a:hover:before{
            border-bottom: 6px solid #04acec;
        }
        .top-nav ul ul{
            top: 0px;
            left: 100px;
        }
        .top-nav ul ul li:first-child>a:before{ 
            border-top: 6px solid transparent;
            border-right: 6px solid #444;
            border-bottom: 6px solid transparent;
            position: absolute;
            top: 20px;
            left: -12px;
        }
        .top-nav ul ul li:first-child>a:hover:before{
            border-bottom: 6px solid transparent;
            border-right: 6px solid #04acec;
        }

    </style>
    <body>
        <ul class="top-nav">
            <li><a href="#">什么都吃</a></li>
            <li><a href="#">肉类</a>
                <ul>
                    <li><a href="#">铁板牛肉</a>
                        <ul>
                            <li><a href="#">黑椒味</a></li>
                            <li><a href="#">孜然味</a></li>
                            <li><a href="#">酸辣味</a></li>
                        </ul>
                    </li>
                    <li><a href="#">泡椒凤爪</a>
                        <ul>
                            <li><a href="#">大盘装</a></li>
                            <li><a href="#">中盘装</a></li>
                            <li><a href="#">小盘装</a></li>
                        </ul>
                    </li>
                    <li><a href="#">坩埚田鸡</a></li>
                </ul>
            </li>
            <li><a href="#">中餐</a>
                <ul>
                    <li><a href="#">家常菜</a>
                        <ul>
                            <li><a href="#">红烧肉</a></li>
                            <li><a href="#">拔丝地瓜</a></li>
                            <li><a href="#">青椒炒肉</a></li>
                        </ul>
                    </li>
                    <li><a href="#">汤</a>
                        <ul>
                            <li><a href="#">花蛤汤</a></li>
                            <li><a href="#">大骨肉汤</a></li>
                            <li><a href="#">鱼汤</a></li>
                        </ul>
                    </li>
                </ul>
            </li>
            <li><a href="#">水果</a></li>
            <li><a href="#">甜点</a></li>

        </ul>
    </body>
</html>

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Because there are many levels...be careful when using selectors. . When should you add > and when should you use spaces. . Otherwise it will take a long time to change, don’t ask me how I know.

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