浅谈 CSS 清除浮动的6种方法_html/css_WEB-ITnose-HTML Tutorial-php.cn

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浅谈 CSS 清除浮动的6种方法_html/css_WEB-ITnose

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Jun 21, 2016 am 09:04 AM

额外标签法

使用:after 伪元素

给父元素定高

利用overflow:hidden;属性

父元素浮动

父元素处于绝对定位

在开发网页的时候经常需要用到各种浮动，此时便需要及时的清除浮动，否则将会导致布局出现问题

引出问题：

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width:300px;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="footer"></div></body></html>

可以看出本应包住3个 inner DIV的 outer DIV 却没有包住他们，此刻只剩一条由上写边框贴合组成的线，同时 footer DIV元素也跑到了三个浮动元素的底下

解决办法：

1.使用额外标签发

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }        .clearfix{            clear: both;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>        <div class="clearfix"></div>    </div>    <div class="footer"></div></body></html>

这是早期普遍使用的方法，但是对于有代码洁癖的人来说，解决的不够完美

2.使用:after 为元素

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }        .clearfix:after{  /*最简方式*/            content: '';            display: block;            clear: both;        }        /* 新浪使用方式        .clearfix:after{             content: '';            display: block;            clear: both;            height: 0;            visibility: hidden;        }        */        .clearfix{ /*兼容 IE*/            zoom: 1;        }    </style></head><body>    <div class="outer clearfix">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="footer"></div></body></html>

3.给父元素定高

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;            height: 50px;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="footer"></div></body></html>

4.利用 overflow:hidden 属性

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;            overflow: hidden;            zoom: 1;/*兼容 IE*/        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="footer"></div></body></html>

5.父元素浮动

当父元素浮动的时候，无需为子元素的浮动清除浮动,布局时经常用到

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;            float: left;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="footer"></div></body></html>

可以看出虽然 outer DIV 消除了塌陷现象，但由于其也发生了浮动故，其后元素若无处于正常文档流，会被跌在底下。
如果要解决可以参考前面的办法。

例如：

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;            float: left;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }        .clearfix:after{            content: "";            display: block;            clear: both;        }        .clearfix{            zoom: 1;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="clearfix"></div>    <div class="footer"></div></body></html>

6.父元素处于绝对定位

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title></title>    <style>        .outer{            border: 1px solid black;            width: 300px;            position: absolute;        }        .inner{            width: 50px;            height: 50px;            background-color: #ff4400;            margin-right: 20px;            float: left;        }        .footer{            background-color: #005FC3;            width: 200px;            height: 100px;        }    </style></head><body>    <div class="outer">        <div class="inner"></div>        <div class="inner"></div>        <div class="inner"></div>    </div>    <div class="clearfix"></div>    <div class="footer"></div></body></html>

与上一个方法同理，由于绝对定位已脱离正常文档流，故出现相同情况，解决办法依旧可以使用以上办法结合，灵活多变。

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