<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>css实现居中的几种方法</title>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
<style>
.parent{
width: 200px;
height: 200px;
background: #ccc;
position: relative;
/*1、flex布局实现。水平居中justify-content，垂直居中align-items*/
display:flex;
justify-content: center;
align-items: center;
}
.child{
width: 50px;
height: 50px;
background: #aaa;
position: absolute;
/*2、margin:auto实现。全居中:auto、水平居中:0 auto、垂直居中：auto 0*/
/*left:0;
top: 0;
bottom: 0;
right: 0;
margin: auto;*/
/*3、Transforms变形实现。left和top值为父级百分比，translate值为自己百分比*/
/*left: 50%;
top: 50%;
transform: translate(-50%,-50%);*/
/*4、margin负间距实现。margin负值为宽高的-1/2*/
/*left: 50%;
top: 50%;
margin-left: -25px;
margin-top: -25px;*/
}
</style>
</body>
</html>