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常用的CSS清除浮动的方法优缺点分析(个人学习笔记)

2016-04-25 11:00:12

一、抛一块问题砖(display: block)先看现象:

    分析HTML代码结构:

<div >  <div >1</div>  <div >2</div>  <div >3</div></div>

  

     分析CSS代码样式:

.outer{border: 1px solid #ccc;background: #fc9;color: #fff; margin: 50px auto;padding: 50px;}.div1{width: 80px;height: 80px;background: red;float: left;}.div2{width: 80px;height: 80px;background: blue;float: left;}.div3{width: 80px;height: 80px;background: sienna;float: left;}

      这里没有给最外层的DIV.outer 设置高度,但是我们知道如果它里面的元素不浮动的话,那么这个外层的高是会自动被撑开的。但是当内层元素浮动后,就出现了一下影响:

    (1):背景不能显示 (2):边框不能撑开 (3):margin 设置值不能正确显示

      当一个内层元素是浮动的时候,如果没有关闭浮动时,其父元素也就不会再包含这个浮动的内层元素,因为此时浮动元素已经脱离了文档流。也就是为什么外层不能被撑开了!

解决办法如下(使用其他代码示例):

1、父级div定义伪类:after和zoom

<style type="text/css">  .div1{background:#000080;border:1px solid red;}  .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px}   .left{float:left;width:20%;height:200px;background:#DDD}  .right{float:right;width:30%;height:80px;background:#DDD}   /*清除浮动代码*/  .clearfloat:after{display:block;clear:both;content:"";visibility:hidden;height:0}  .clearfloat{zoom:1}  </style> <div class="div1 clearfloat"> <div class="left">Left</div> <div class="right">Right</div> </div><div class="div2">  div2  </div>

 

2、结尾处加空div标签clear:both

<style type="text/css">  .div1{background:#000080;border:1px solid red}  .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px}   .left{float:left;width:20%;height:200px;background:#DDD}  .right{float:right;width:30%;height:80px;background:#DDD}   /*清除浮动代码*/  .clearfloat{clear:both}  </style> <div class="div1"> <div class="left">Left</div> <div class="right">Right</div><div class="clearfloat"></div></div><div class="div2">  div2  </div>

 

3、父级div定义overflow:hidden

<style type="text/css">  .div1{background:#000080;border:1px solid red;/*解决代码*/width:98%;overflow:hidden}  .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px;width:98%}   .left{float:left;width:20%;height:200px;background:#DDD}  .right{float:right;width:30%;height:80px;background:#DDD}  </style> <div class="div1"> <div class="left">Left</div> <div class="right">Right</div></div><div class="div2">  div2  </div>

4、父级div定义overflow:auto

<style type="text/css">  .div1{background:#000080;border:1px solid red;/*解决代码*/width:98%;overflow:auto}  .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px;width:98%}   .left{float:left;width:20%;height:200px;background:#DDD}  .right{float:right;width:30%;height:80px;background:#DDD}  </style> <div class="div1"> <div class="left">Left</div> <div class="right">Right</div></div><div class="div2">  div2  </div>

5、父级div定义height

<style type="text/css">  .div1{background:#000080;border:1px solid red;/*解决代码*/height:200px;}  .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px}   .left{float:left;width:20%;height:200px;background:#DDD}  .right{float:right;width:30%;height:80px;background:#DDD}  </style> <div class="div1"> <div class="left">Left</div> <div class="right">Right</div> </div><div class="div2">  div2  </div>