HTML
<div class="fater">
<div class="sum"></div>
</div>
方式一: 父级相对 子级绝对
要求子级宽度设置
<style>
.fater{
width: 500px;
height: 500px;
border: 1px solid black;
position: relative;
}
.sum{
width: 100px;
height: 100px;
background: red;
position: absolute;
left: 50%;
top: 50%;
margin-left: -50px;
margin-top: -50px;
}
</style>
方式二:transform:translate(-50%);
宽高不确定,transform是css3属性注意兼容性问题
<style>
.fater{
width: 500px;
height: 500px;
border: 1px solid black;
position: relative;
}
.sum{
width: 100px;
height: 100px;
background: red;
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%);
}
</style>
方式三
子级宽高不确定
<style>
.fater{
width: 500px;
height: 500px;
border: 1px solid black;
position: relative;
}
.sum{
width: 100px;
height: 100px;
background: red;
position: absolute;
left: 0;
top: 0;
right: 0;
bottom: 0;
margin: auto;
}
</style>
方式四:flex布局
<style>
.fater{
width: 500px;
height: 500px;
border: 1px solid black;
display: flex;
align-items: center;
justify-content: center;
}
.sum{
width: 100px;
height: 100px;
background: red;
}
</style>