垂直居中
1. display:flex
- 通过
display:flex实现CSS垂直居中的方法是给父元素display:flex;而子元素align-self:center;
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
display: flex;
}
.in{
background-color: green;
width: 50%;
height: 50%;
align-self: center;
}
</style>
</head>
<body>
<div class="box">
<div class="in"></div>
</div>
</body>
</html>
2. :before
- 为父元素添加伪元素
:before，使得子元素实现垂直居中。
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
}
.box:before{
content: "";
display: inline-block;
vertical-align: middle;
height: 100%;
}
.in{
background-color: green;
width: 50%;
height: 50%;
display: inline-block;
vertical-align: middle;
}
</style>
</head>
<body>
<div class="box">
<div class="in"></div>
</div>
</body>
</html>
3. 隐藏节点
- 创建一个隐藏节点
.hide，使得隐藏节点的height值为剩余高度的一半
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
}
.hide{
width: 50%;
height: 25%;
}
.in{
background-color: green;
width: 50%;
height: 50%;
}
</style>
</head>
<body>
<div class="box">
<div class="hide"></div>
<div class="in"></div>
</div>
</body>
</html>
4. transform(已知父元素高度)
- 给子元素的
position:relative，再通过translateY即可定位到垂直居中的位置。
- 必须知道父元素高度
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
}
.in{
background-color: green;
width: 50%;
height: 50%;
position: relative;
top: 50%;
transform: translateY(-50%);
}
</style>
</head>
<body>
<div class="box">
<div class="in"></div>
</div>
</body>
</html>
5. transform(未知父元素高度)
- 先给父元素
position:relative，再给子元素position:absolute，通过translateY即可定位到垂直居中的位置
- 无需知道父元素高度
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
position: relative;
}
.in{
background-color: green;
width: 50%;
height: 50%;
position: absolute;
top: 50%;
transform: translateY(-50%);
}
</style>
</head>
<body>
<div class="box">
<div class="in"></div>
</div>
</body>
</html>
6. margin
- 给子元素添加
margin: 0 auto;
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
}
.in{
background-color: green;
width: 50%;
height: 50%;
margin: 0 auto;
}
</style>
</head>
<body>
<div class="box">
<div class="in"></div>
</div>
</body>
</html>
7. line-height
- 适用于文本
- 设置子元素的
line-height值等于父元素的height，这种方法适用于子元素为单行文本的情况
- 代码实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box{
background-color: yellow;
width: 300px;
height: 300px;
position: relative;
}
.in{
width: 50%;
height: 50%;
line-height: 300px;
}
</style>
</head>
<body>
<div class="box">
<div class="in">hello world</div>
</div>
</body>
</html>