水平垂直居中
<div class="box">
<div class="content"></div>
</div>
/*position 元素已知宽度*/
<style>
.box {
background-color: #FF8C00;
width: 300px;
height: 300px;
position: relative;
}
.content {
background-color: #F00;
width: 100px;
height: 100px;
position: absolute;
left: 50%;
top: 50%;
margin: -50px 0 0 -50px;
}
</style>
<style>
.box {
background-color: #FF8C00;
width: 300px;
height: 300px;
position:relative;
}
.content {
background-color: #F00;
width: 100px;
height: 100px;
position: absolute;
top:0;
left:0;
bottom:0;
right:0;
margin:auto;
}
</style>
/*position transform*/
<!--可能在有些设备中会存在差了半像素的情况-->
<style>
.box {
background-color: #FF8C00;
width: 300px;
height: 300px;
position: relative;
}
.content {
background-color: #F00;
width: 100px;
height: 100px;
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%,-50%);
}
</style>
/*flex布局*/
<style>
.box {
background-color: #FF8C00;
width: 300px;
height: 300px;
display: flex;
justify-content: center;
align-items: center;
}
.content {
background-color: #F00;
width: 100px;
height: 100px;
}
</style>
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分割线
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<!-- 还有一种可能遇到的居中效果，浮动居中 -->
<style>
.box {
background-color: #FF8C00;
clear: left;
float: left;
position: relative;
left: 50%;
}
.content {
background-color: #F00;
width: 100px;
height: 100px;
position: relative;
float: left;
right:50%;
}
</style>
