CSS等高布局的7种方式

  等高布局是指子元素在父元素中高度相等的布局方式。等高布局的实现包括伪等高和真等高,伪等高只是看上去等高而已,真等高是实实在在的等高。本文将介绍边框模拟、负margin这两种伪等高以及table实现、absolute实现、flex实现、grid实现和js判断这五种真等高布局

 

伪等高

边框模拟

  因为元素边框和元素高度始终是相同高度,用元素的边框颜色来伪装左右两个兄弟元素的背景色。然后将左右两个透明背景的元素使用absolute覆盖在中间元素的左右边框上,实现视觉上的等高效果

  [注意]左右两侧元素的内容高度不能大于中间元素内容高度,否则无法撑开容器高度

<style>
body,p{margin: 0;}
.parent{
    position: relative;
}
.center{
    box-sizing:border-box;
    padding: 0 20px;
    background-clip: content-box;
    border-left: 210px solid lightblue;
    border-right: 310px solid lightgreen;
}
.left{
    position: absolute;
    top: 0;
    left: 0;
    width: 200px;
}
.right{
    position: absolute;
    top: 0;
    right: 0;
    width: 300px;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left">
        <p>left</p>
    </div>  
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>          
    <div class="right">
        <p>right</p>
    </div>        
</div>

 

负margin

  因为背景是在padding区域显示的,设置一个大数值的padding-bottom,再设置相同数值的负的margin-bottom,使背景色铺满元素区域,又符合元素的盒模型的计算公式,实现视觉上的等高效果

  [注意]如果页面中使用<a>锚点跳转时,将会隐藏部分文字信息

  [注意]如果页面中的背景图片定位到底部,将会看不到背景图片

<style>
body,p{margin: 0;}
.parent{
    overflow: hidden;
}
.left,.centerWrap,.right{
    float: left;
    width: 50%;
    padding-bottom: 9999px;
    margin-bottom: -9999px;
}
.center{
    margin: 0 20px;
}
.left,.right{
    width: 25%;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="centerWrap">
        <div class="center" style="background-color: pink;">
            <p>center</p>
            <p>center</p>
        </div>         
    </div>

    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>

 

真等高

table

  table元素中的table-cell元素默认就是等高的

<style>
body,p{margin: 0;}
.parent{
    display: table;
    width: 100%;
    table-layout: fixed;
}
.left,.centerWrap,.right{
    display: table-cell;
}
.center{
    margin: 0 20px;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="centerWrap">
        <div class="center" style="background-color: pink;">
            <p>center</p>
            <p>center</p>
        </div>         
    </div> 
    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>

 

absolute

  设置子元素的top:0;bottom:0;使得所有子元素的高度都和父元素的高度相同,实现等高效果

<style>
body,p{margin: 0;}
.parent{
    position: relative;
    height: 40px;
}
.left,.center,.right{
    position: absolute;
    top: 0;
    bottom: 0;
}
.left{
    left: 0;
    width: 100px;
}
.center{
    left: 120px;
    right: 120px;
}
.right{
    width: 100px;
    right: 0;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>          
    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>

 

flex

  flex中的伸缩项目默认都拉伸为父元素的高度,也实现了等高效果

<style>
body,p{margin: 0;}
.parent{
    display: flex;
}
.left,.center,.right{
    flex: 1;
}
.center{
    margin: 0 20px;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>          
    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>

 

grid

<style>
body,p{margin: 0;}
.parent{
    display: grid;
    grid-auto-flow: column;
    grid-gap:20px;
}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>          
    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>

 

js

  当子元素高度不同时,进行js判断,增加较低子元素的padding-bottom,使得各个子元素实现等高效果

<style>
body,p{margin: 0;}
.parent{overflow: hidden;}
.left,.center,.right{
    float: left;
    width: 25%;
}    
.center{
    width: 50%;
    padding: 0 20px;
    background-clip: content-box;
    box-sizing: border-box;
}
</style>
<div class="parent" id="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
    </div>  
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>          
    <div class="right" style="background-color: lightgreen;">
        <p>right</p>
    </div>        
</div>
<script>
function getCSS(obj,style){
    if(window.getComputedStyle){
        return getComputedStyle(obj)[style];
    }
    return obj.currentStyle[style];
}
var oParent = document.getElementById('parent');
var oLeft = oParent.getElementsByTagName('div')[0];
var oCenter = oParent.getElementsByTagName('div')[1];
var oRight = oParent.getElementsByTagName('div')[2];
function eqHeight(obj1,obj2){
    var oDis = obj1.clientHeight - obj2.clientHeight;
    if(oDis > 0){
        obj2.style.paddingBottom = parseFloat(getCSS(obj2,'padding-bottom')) + oDis + 'px';
    }else{
        obj1.style.paddingBottom = parseFloat(getCSS(obj1,'padding-bottom')) +  Math.abs(oDis) + 'px';
    }
}
eqHeight(oLeft,oCenter);
eqHeight(oLeft,oRight);
</script>

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