居中位置：固定元素 [英] Center a position:fixed element
问题描述
我想让一个 position：fixed; 弹出框以屏幕动态宽度和高度为中心。我使用 margin：5％auto; 。没有 position：fixed; 它水平居中，但不垂直。
I would like to make a position: fixed; popup box centered to the screen with a dynamic width and height. I used margin: 5% auto; for this. Without position: fixed; it centers fine horizontally, but not vertically. After adding position: fixed;, it's even not centering horizontally.
这是完整的集合：
.jqbox_innerhtml {
position: fixed;
width: 500px;
height: 200px;
margin: 5% auto;
padding: 10px;
border: 5px solid #ccc;
background-color: #fff;
}
<div class="jqbox_innerhtml">
This should be inside a horizontally
and vertically centered box.
</div>
如何在CSS中将此框置于屏幕中？
How do I center this box in screen with CSS?
推荐答案
您基本上需要设置顶部和左到 50％以div的左上角为中心。您还需要将 margin-top 和 margin-left 设置为div的高度和宽度的负的一半
You basically need to set top and left to 50% to center the left-top corner of the div. You also need to set the margin-top and margin-left to the negative half of the div's height and width to shift the center towards the middle of the div.
因此，提供<！DOCTYPE html> 模式），这应该：
Thus, provided a <!DOCTYPE html> (standards mode), this should do:
position: fixed;
width: 500px;
height: 200px;
top: 50%;
left: 50%;
margin-top: -100px; /* Negative half of height. */
margin-left: -250px; /* Negative half of width. */
或者，如果你不关心垂直和旧的浏览器如IE6 / 7 ，那么您也可以向具有 right：0 > $ > ，使得固定定位的元素具有固定宽度知道它的左和右偏移在哪里开始。在您的情况下：
Or, if you don't care about centering vertically and old browsers such as IE6/7, then you can instead also add left: 0 and right: 0 to the element having a margin-left and margin-right of auto, so that the fixed positioned element having a fixed width knows where its left and right offsets start. In your case thus:
position: fixed;
width: 500px;
height: 200px;
margin: 5% auto; /* Will not center vertically and won't work in IE6/7. */
left: 0;
right: 0;
同样，这只能在IE8 +中使用，如果你关心IE，它只是水平不垂直。
Again, this works only in IE8+ if you care about IE, and this centers only horizontally not vertically.
这篇关于居中位置：固定元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
