元素垂直或居中定位

HTML格式为

<div class="parent">
    <div class="child">Test</div>    
<div>

下面的styles 皆为.child所用。

1. 垂直定位

inline element:

selector{inline-height: parent-height;} 

block element:

div_with_exact_height{
    position: absolute;
    height: 50px;
    margin-top: auto;
    margin-bottom: auto;
    top: 0;
    bottom: 0;      
}

div_can_stretch{
    position: absolute;
    height: auto;
    margin-top: 10px;
    margin-bottom: 10px;
    top: 0;
    bottom: 0;
}

2. 水平居中

(1) position: static/relative

div_with_exact_width{
    width: 50px;
    text-align: center;
    margin-left: auto;
    margin-right: auto;
}

div_can_stretch{
    width: auto;
    text-align: center;
    margin-left: 20px;
    margin-right: 20px;
}

(2) position: absolute;

div_with_exact_width{
    position: absolute;
    width: 50px;
    margin-left: auto;
    margin-right: auto;
    left: 0;
    right: 0;
}

div_can_stretch{
    position: absolute;
    width: auto;
    margin-left: 20px;
    margin-right: 20px;
    left: 0;
    right: 0;
}