Flexbox，绝对定位和100％高度

Question

I've run into a bit of a problem while playing around with a flexbox inside an absolute box, which is inside a defined height div (I'll explain along the way).

First off, here's a fiddle to my demo, might be easier to grasp the problem: https://jsfiddle.net/8ub9tyub/

As you can see, when you hover the block, text appears from below but doesn't quite show fully.

I have a main div (let's call it $main ) for the hover part which is 600x250px with an overflow: hidden , and inside it, two divs: title and text (say $title and $text ), which appear after one another (regular flow).

$title can sometimes take up two lines, so its height is set to auto. $text is set to 100% height, positioned in relative and set to display: flex . Inside that is another div ( $intro ) I positioned in absolute, with a top: 100% (which switches to 0 when hovered) and a align-self: flex-end in order to keep it at the bottom of $main . (this is to keep the text from being stuck to the title - I like it to breathe)

The structure goes like this, basically:

<div class="main">
 <div class="title">I'm a title!</div>
 <div class="text">
  <div class="intro"><p>Just a bunch of long paragraphs of text</p></div>
 </div>
</div>

Now, as you can see on my demo, $text 's height is set to 100%, but I expected the height to be $main minus $title 's heights, but here it seems to be just $main 's height, which makes the $text block overflow, and so when I hover the block to make the text appear, it locks the bottom outside $main and cuts off part of the text.

Would anyone have a clue has to how I can make $text have the expected height, knowing I can't predict $title 's height (and thus can't use calc() , at least as for as I know) and I don't want to use JavaScript in any way?

Answer 1

I've gone through and reworked the code without using any heights for the block text or the title text and only using Flex. If you use display: flex; only on the container that will contain the flexible items within it, then tell each item how to be flexible (ie. flex-grow: 1; ), you'll get the result you're looking for. Here's a link to a fiddle I put together using your initial code and just reworking the code. Let me know if you have any questions or need clarification on anything.

 body { font-family: 'Bitter', Georgia, serif; width: 673px; } a { color: #161616; text-decoration: none; } * { box-sizing: border-box; } .home_post_new * { transition: .5s all; } .home_post_new { background-position: right center; background-repeat: no-repeat; width: 100%; height: 250px; position: relative; overflow: hidden; margin-bottom: 20px; } .home_post_new_text { float: right; display: flex; flex-direction: column; width: 600px; height: 100%; background: hsla(0,0%,100%,0); color: #fff; position: relative; } .home_post_new:hover .home_post_new_text { background: hsla(0,0%,0%,.33); } .home_post_new_block { flex-grow: 2; position: relative; top: 250px; width: 100%; padding: 16px 16px 32px; font-size: .9em; line-height: 125%; text-shadow: 0 1px 0 hsla(0,0%,0%,.75), 0 0 5px hsla(0,0%,0%,.75); } .home_post_new:hover .home_post_new_block { top: 0; } .home_post_new_title { flex-grow: 1; font-family: 'Source Sans Pro', Arial, sans-serif; font-size: 1.625em; line-height: 1.333em; width: 100%; padding: 4px 8px 16px; text-shadow: 0 1px 0 hsla(0,0%,0%,.75), 0 0 1px hsla(0,0%,0%,.75), 0 1px 5px hsla(0,0%,0%,.75); background: -moz-linear-gradient(top, rgba(0,0,0,0.65) 0%, rgba(0,0,0,0) 100%); background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(0,0,0,0.65)), color-stop(100%,rgba(0,0,0,0))); background: -webkit-linear-gradient(top, rgba(0,0,0,0.65) 0%,rgba(0,0,0,0) 100%); background: -o-linear-gradient(top, rgba(0,0,0,0.65) 0%,rgba(0,0,0,0) 100%); background: -ms-linear-gradient(top, rgba(0,0,0,0.65) 0%,rgba(0,0,0,0) 100%); background: linear-gradient(to bottom, rgba(0,0,0,0.65) 0%,rgba(0,0,0,0) 100%); } .home_post_new_more { position: absolute; right: 0; bottom: -50%; padding: 4px 8px; font-family: 'Source Sans Pro', Arial, sans-serif; color: #fff; text-shadow: 0 1px 0 hsla(0,0%,0%,.75), 0 0 5px hsla(0,0%,0%,.75); border-style: solid; border-width: 1px 0 0 1px; border-color: currentColor; border-radius: 0; border-top-left-radius: 2px; text-transform: uppercase; letter-spacing: 1px; background: hsla(0,0%,0%, .5); } .home_post_new_more:hover { color: #009884; cursor: pointer; } .home_post_new:hover .home_post_new_more { bottom: 0; } .home_post_new_meta { width: calc(100% - 600px); height: 100%; text-align: center; color: #009884; } .home_post_new_date { background: #009884; color: #eee; padding: 24px 0 0; height: 50%; } .home_post_new_date_day { font-size: 250%; font-weight: bold; } .home_post_new_date_month { font-family: 'Source Sans Pro', Arial, sans-serif; text-transform: uppercase; font-size: 150%; border-top: 1px solid #eee; display: inline-block; margin-top: 8px; padding-top: 4px; } .home_post_new_date_comments { color: currentColor; display: inline-block; border-radius: 50%; border-bottom-right-radius: 0; width: 42px; height: 42px; margin-top: 32px; padding: 12px 4px; border: 1px solid currentColor; margin-top: calc(50% - 4px); } .home_post_new_text:after { clear: both; overflow: auto; zoom: 1; } 

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Answer 2

So let me get this straight you have:

<div class='main'>
    <div class='title'>
        <div class='text'></div>
    </div>
</div>

And setting the height of div text to 100% sets it to the height of main even though it's inside div title . I think the problem might be that you did not specify the height of .title in your CSS. If you do not specify the height of the title div, then the text division will take on the height of the main div.

Again, just a guess but check for that.