实现代码:
<!DOCTYPE html>
<html>
<head>
<title>垂直居中</title>
<meta charset="utf-8">
<script type="text/javascript"></script>
<style type="text/css">
/* 方法 1 子元素 position:absolute 0 0 0 0*/
#container1{
400px;
height: 400px;
position: relative;
background-color: #f5f5f5;
}
#item1{
200px;
height: 200px;
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
background-color: #03c03c;
}
/* 方法 2 子元素 position:absolute*/
#container2{
margin-top: 20px;
400px;
height: 400px;
position: relative;
background-color: #f5f5f5;
}
#item2{
200px;
height: 200px;
position: absolute;
left: 50%;
margin-left: -100px;
top: 50%;
margin-top: -100px;
background-color: #03c03c;
}
/* 方法 3 子元素 position:relative*/
#container3{
position: relative;
margin-top: 20px;
400px;
height: 400px;
background-color: #f5f5f5;
}
#item3{
200px;
height: 200px;
position: relative;
left: 50%;
margin-left: -100px;
top: 50%;
margin-top: -100px;
background-color: #03c03c;
}
/* 方法 4 line-height*/
#container4{
400px;
height: 400px;
line-height: 100px;
background-color: #f5f5f5;
margin-top: 20px;
}
#item4{
200px;
height: 200px;
margin: 0 auto;
background-color: #03c03c;
}
/* 方法 5 display:flex*/
#container5{
400px;
height: 400px;
display: flex;
align-items: center;
justify-content: center;
background-color: #f5f5f5;
margin-top: 20px;
}
#item5{
200px;
height: 200px;
background-color: #03c03c;
}
/* 方法 6 display:box; */
#container6{
height: 400px;
400px;
margin-top: 20px;
background-color: #f5f5f5;
display: -webkit-box;
display: box;
-webkit-box-align: center;
-webkit-box-pack: center;
box-align: center;
box-pack: center;
}
#item6{
height: 200px;
200px;
background-color: #03c03c;
}
</style>
</head>
<body>
<div id="container1">CONTAINER1
<div id="item1">ITEM1</div>
</div>
<div id="container2">CONTAINER2
<div id="item2">ITEM2</div>
</div>
<div id="container3">CONTAINER3
<div id="item3">ITEM3</div>
</div>
<div id="container4">CONTAINER4
<div id="item4">ITEM4</div>
</div>
<div id="container5">
<div id="item5"></div>
</div>
<div id="container6">
<div id="item6"></div>
</div>
</body>
</html>