Let's say I have two divs, one inside the other, like so:
<html>
<body>
<div id="outer" style="width:50%">
<div id="inner" style="width:100%">
</div>
</div>
</body>
</html>
Right now, the inner div has a width of 100% of 50% of the screen size, or 50% of the screen size. If I were to change the inner div to position absolute, like this:
<html>
<body>
<div id="outer" style="width:50%">
<div id="inner" style="position:absolute;width:100%">
</div>
</div>
</body>
</html>
In this case the inner div takes up 100% of the screen space, because its position is set to absolute.
My question is this: Is there any way to maintain relative width of the inner div while its position is set to absolute?
Add position:relative to your outer div.
update: It works because positions in position: absolute are relative to the first parent that has some positioning (other than static). In this case there was no such container, so it uses the page.
Yes. Set outer to position: relative.
.outer
{
width: 50%;
height: 200px;
position: relative;
border: 1px solid red;
}
.inner
{
width: 100%;
position: absolute;
height: 100%;
border: 1px solid blue;
}
来源：https://stackoverflow.com/questions/14327104/is-there-any-way-for-positionabsolute-div-to-retain-relative-width