先看图
代码如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
span{
font-size: 17px;
}
.main{
display: flex;
flex-wrap: wrap;
}
.demo {
width: 300px;
height: 300px;
border: 1px solid purple;
display: flex;
justify-content: center;
/*水平居中*/
align-items: center;
/*垂直居中*/
}
.inner {
width: 100px;
height: 100px;
font-size: 26px;
border: 1px solid red;
background-color: antiquewhite;
}
.demo2 {
width: 300px;
height: 300px;
border: 1px solid red;
position: relative;
}
.inner2 {
width: 100px;
height:100px;
border: 1px solid black;
background-color: greenyellow;
position: absolute;
margin: 0 auto;
left:0;
right:0;
/* top:0; */
/* bottom:0 */
}
.demo3 {
width: 300px;
height: 300px;
border: 1px solid red;
position: relative;
}
.inner3 {
width: 100px;
height:100px;
border: 1px solid black;
background-color: greenyellow;
position: absolute;
margin-top: auto;
margin-bottom: auto;
top:0;
bottom:0;
}
.demo4 {
width: 300px;
height: 300px;
border: 1px solid red;
position: relative;
}
.inner4 {
width: 100px;
height:100px;
border: 1px solid black;
background-color: greenyellow;
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
}
</style>
</head>
<body>
<div class="main">
<div class="demo">
<div class="inner">
<span>demo:</br>flex垂直居中</p>
</div>
</div>
<div class="demo2">
<div class="inner2">
<span>demo2:<br />
绝对定位水平居中</span>
</div>
</div>
<div class="demo3">
<div class="inner3">
<span>demo3:<br />绝对定位垂直居中</span>
</div>
</div>
<div class="demo4">
<div class="inner4">
<span>demo4:<br />绝对定位水平垂直居中</span>
</div>
</div>
</div>
</body>
</html>
可参考文章
1.水平垂直居中——position与margin的结合使用