1、绝对定位 + translate
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.parent1 {
position: relative;
width: 200px;
height: 200px;
background-color: antiquewhite;
}
.son1 {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%,-50%);
width: 20px;
height: 20px;
background-color: aqua;
}
</style>
</head>
<body>
<div class="parent1">
<div class="son1"></div>
</div>
</body>
</html>
2、绝对定位和负边距
.parent1 {
position: relative;
width: 200px;
height: 200px;
background-color: antiquewhite;
}
.son1 {
position: absolute;
top: 50%;
left: 50%;
margin-left:-10px;
margin-top:-10px;
width: 20px;
height: 20px;
background-color: aqua;
}
3、display:flex
.box2{
display: flex;
justify-content:center;
align-items:Center;
}