1. 绝对定位+margin:auto的方式
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: rgba(255,0,0,1);
position: relative;
}
.child {
width: 50%;
height: 50%;
background-color: rgba(0,255,0,1);
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
</body>
</html>2. 绝对定位+transform:translate(-50%, -50%)的方式
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: rgba(255,0,0,1);
position: relative;
}
.child {
width: 50%;
height: 50%;
background-color: rgba(0,255,0,1);
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
</body>
</html>3. 绝对定位+设置左和上的外边距（需要知道子块宽高具体值）的方式
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: rgba(255,0,0,1);
position: relative;
}
.child {
width: 100px;
height: 100px;
background-color: rgba(0,255,0,1);
position: absolute;
top: 50%;
left: 50%;
margin-top: -50px;
margin-left: -50px;
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
</body>
</html>4. 父块display: table-cell + vertical-align + 子块margin的方式
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: rgba(255,0,0,1);
display: table-cell;
vertical-align: middle;
}
.child {
width: 50%;
height: 50%;
background-color: rgba(0,255,0,1);
margin: 0 auto;
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
</body>
</html>5. flex布局方式
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: rgba(255,0,0,1);
display: flex;
justify-content: center;
align-items: center;
}
.child {
width: 50%;
height: 50%;
background-color: rgba(0,255,0,1);
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
</div>
</body>
</html>以上2,4,5方式，注意浏览器版本，较老版本浏览器可能不兼容。
注：以上，如有不合理之处，还请帮忙指出，大家一起交流学习~
