为什么当位置是相对的时，height和top属性不工作？ [英] why does height and top attribute not work when position is relative?

问题描述

这会将框定位在顶部以下

This will position the box a little below the top

<div style="height: 10em; width: 50%; left: 25%; top:2em; position: relative; background: white;">Hello World</div>

这将把框放在顶部附近，它看起来不像height和top属性

工作。箱子的高度不是50％，箱子不是顶部以下50％。

This will position the box near the top and it looks like neither the height nor top property is
working. The height of the box is not 50%, and the box is not 50% below the top.

<div style="height: 50%; width: 50%; left: 25%; top:20%; position: relative; background: white;">Hello World</div>

我是一个初学者在这个东西，但它似乎如果左和宽工作与百分比不应高于和高度？

I am pretty much a beginner at this stuff, but it would seem if left and width work with a percentage shouldn't top and height?

推荐答案

您的盒子不能有 c $ c>是父级的父级的一个百分比，如果它的父级没有固定的高度，因为然后框不知道它需要多高（通常这样的父级将 body 或一些其他包装器元素）。

Your box can't have a height that's a percentage of its parent if its parent doesn't have a fixed height, because then the box wouldn't know how high it needs to be (typically such a parent would be body or some other wrapper element).

作为直接的结果， top 也不会有任何效果。

As a direct consequence, top with a percentage won't have any effect either.

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