已知高度和寬度的元素
- 方案一:設置父元素爲相對定位,給子元素設置絕對定位,top: 0; right: 0; bottom: 0; left: 0; margin: auto;
<style>
#father {
width: 500px;
height: 300px;
background-color: skyblue;
position: relative;
}
#son {
width: 100px;
height: 100px;
background-color: green;
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
</style>
<div id="father">
<div id="son">我是塊級元素</div>
</div>
- 方案二:設置父元素爲相對定位,給子元素設置絕對定位,left: 50%; top: 50%; margin-left: --元素寬度的一半px; margin-top: --元素高度的一半px;
<style>
#father {
width: 500px;
height: 300px;
background-color: skyblue;
position: relative;
}
#son {
width: 100px;
height: 100px;
background-color: green;
position: absolute;
left: 50%;
top: 50%;
margin-left: -50px;
margin-top: -50px;
}
</style>
<div id="father">
<div id="son">我是塊級元素</div>
</div>
未知高度和寬度的元素
- 方案一:使用定位屬性 ;
設置父元素爲相對定位,給子元素設置絕對定位,left: 50%; top: 50%; transform: translateX(-50%) translateY(-50%);
<style>
#father {
width: 500px;
height: 300px;
background-color: skyblue;
position: relative;
}
#son {
background-color: green;
position: absolute;
left: 50%;
top: 50%;
transform: translateX(-50%) translateY(-50%);
}
</style>
<div id="father">
<div id="son">我是塊級元素</div>
</div>
- 方案二:使用flex佈局實現
設置父元素爲flex定位,justify-content: center; align-items: center;
<style>
#father {
width: 500px;
height: 300px;
background-color: skyblue;
display: flex;
justify-content: center;
align-items: center;
}
#son {
background-color: green;
}
</style>
<div id="father">
<div id="son">我是塊級元素</div>
</div>