理解css 中的position五个属性_html/css_WEB-ITnose-HTML Tutorial-php.cn

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理解css 中的position五个属性_html/css_WEB-ITnose

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Jun 24, 2016 am 11:32 AM

在实际开发页面布局时，运用position，对定位的块级元素的嵌套的效果总是不太理解，这里做了几个测试

一般的在w3c中我们可以很容易的获取定义:

static ：默认值。没有定位，元素出现在正常的流中（忽略 top, bottom, left, right 或者 z-index 声明）。

fixed ：生成绝对定位的元素，相对于浏览器窗口进行定位。元素的位置通过 "left", "top", "right" 以及 "bottom" 属性进行规定。

inherit　：规定应该从父元素继承 position 属性的值。

absolute : 生成绝对定位的元素，相对于 static 定位以外的第一个父元素进行定位。元素的位置通过 "left", "top", "right" 以及 "bottom" 属性进行规定。

relative : 生成相对定位的元素，相对于其正常位置进行定位。因此，"left:20" 会向元素的 LEFT 位置添加 20 像素。

总的来说：

static呢，就是正常的文档流顺序，默认的，相当于没有定位!

fixed呢，就是相对于浏览器窗口，就是你滚动条怎么滚动，他还是那个位置，就想是 “粘” 在窗口上了!

　　inherit呢，就是从父元素继承 position 属性的值，

absolute呢，是脱离文档流的原来的位置是不继续占据了，如果他的父级元素中有已经定位了的不管是absolute的还是relative，它都会相对于他的父级元素来定位，如果他的父级元素中没有定位了的那么它就是相对于body来定位的。也就是说absolute的绝对是有参照物的！

relative呢，是不会脱离文档流的原来的位置也就继续占据了，它是只相对于自身原来的位置来定位的!

　　前三个是很容易理解的，对于absolute和relative的结合使用，做了几个测试

测试（absolute和relative）

　　1.单独的absolute和relative

　　2.relative中的relative，absolute中的relative

　　3.absolute中的absolute，relative中的absolute

<!DOCTYPE html><html><head>	<title>position -- absolute -- relative</title></head><style>		.test-a{		position: absolute;		top:20px;		left:60px;		width:200px;		height: 100px;		background: red;	}	.test{		width:400px;		height: 100px;		background: green;	}	.test-r{		position:relative;		top:50px;		left:130px;		background: yellow;		width:160px;		height: 180px;	}	.test-rr{	    position: relative;	    top: 20px;	    left: 100px;	    width: 600px;	    height: 300px;	    background: blue;	}	.test-aa{		position: absolute;	    top: 24px;	    left: 34px;	    background: orange;	}	.test-aaa{		position: absolute;	    top: 24px;	    left: 34px;	    width:400px;	    height:200px;	    background: #18E457;	}	.test-aaaa{		position: absolute;	    top: 124px;	    left: 134px;	    width:400px;	    height:200px;	    background: yellow;	}	.test-rrr{		position: relative;	    top: 24px;	    left: 34px;	    width:400px;	    height:200px;	    background: yellow;	}	.test-rrr{		position: relative;	    top: 124px;	    left: 134px;	    width:400px;	    height:200px;	    background: red;	}	.test-r-a{		position: absolute;	    top: 124px;	    left: 134px;	    width:800px;	    height:800px;	    background: yellow;	}	.test-a-r{		position: relative;	    top: 124px;	    left: 134px;	    width:700px;	    height:700px;	    background: red;	}</style><body>	<div class="test-a">absolute</div>	<div class="test">分割</div>	<div class="test-r">relative</div>	<h2 id="结合使用">结合使用</h2>	<p>parentNode的position不是relative或absolute,那absolute的绝对对象是针对body的 	  parentNode的position  是relative或absolute,那absolute的绝对对象是针对parentNode的 	  也就是说absolute的绝对是有参照Node的 </p>	<div class="test-rr">		absolute外的relative		<div class="test-aa">			relative内的absolute，，，里面这个div是相对外面那个div定位的		</div>	</div>	<div class="test-aaa">			absolute外的absolute			<div class="test-aaaa">				absolute内的absolute,,,,,,,,里面这个div是相对外面那个div定位的			</div>	</div>	<div class="test-rrr" >			relative外的relative			<div class="test-rrrr">				relative内的relative,,,,,,,,里面这个div是相对原来位置定位的			</div>	</div>	<div class="test-r-a">		relative外的absolute		<div class="test">								<div class="test-a-r">				relative内的absolute，，，里面这个div是相对原来位置定位的			</div>		</div>	</div></body></html>

　　其实很多时候，网上的经验，很多很杂，自己实践一下，才能自己真正理解

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