我遇到了一个奇怪的布局问题，想不出办法解决。标题可能有点令人困惑，但让我展示代码。
#root-container {
display: flex;
}
#container1 {
width: 100px;
height: 500px;
background-color: grey;
}
#sticky-container {
width: 320px;
max-height: 500px;
position: relative;
background-color: lightgrey;
}
#sticky-container-header {
width: 320px;
height: 100px;
background-color: #2f4d92;
}
#full-height-content {
width: 100%;
height: 400px;
overflow-y: scroll;
background-color: #d67e23;
}
#sticky-content {
width: 80%;
height: 100px;
position: sticky;
bottom: 20px;
background-color: rgba(0,0,0,0.5);
}
#bottom {
width: 420px;
height: 100px;
background-color: purple;
}<div id='root-container'>
<div id="container1"></div>
<div id="sticky-container">
<div id='sticky-container-header'></div>
<div id='full-height-content'>
Saw yet kindness too replying whatever marianne. Old sentiments resolution admiration unaffected its mrs literature. Behaviour new set existence dashwoods. It satisfied to mr commanded consisted disposing engrossed. Tall snug do of till on easy. Form not calm new fail.
His followed carriage proposal entrance directly had elegance. Greater for cottage gay parties natural. Remaining he furniture on he discourse suspected perpetual. Power dried her taken place day ought the. Four and our ham west miss. Education shameless who middleton agreement how. We in found world chief is at means weeks smile.
Instrument cultivated alteration any favourable expression law far nor. Both new like tore but year. An from mean on with when sing pain. Oh to as principles devonshire companions unsatiable an delightful. The ourselves suffering the sincerity. Inhabit her manners adapted age certain. Debating offended at branched striking be subjects.
Must you with him from him her were more. In eldest be it result should remark vanity square. Unpleasant especially assistance sufficient he comparison so inquietude. Branch one shy edward stairs turned has law wonder horses. Devonshire invitation discovered out indulgence the excellence preference. Objection estimable discourse procuring he he remaining on distrusts. Simplicity affronting inquietude for now sympathize age. She meant new their sex could defer child. An lose at quit to life do dull.
Surrounded affronting favourable no mr. Lain knew like half she yet joy. Be than dull as seen very shot. Attachment ye so am travelling estimating projecting is. Off fat address attacks his besides. Suitable settling mr attended no doubtful feelings. Any over for say bore such sold five but hung.
Lose john poor same it case do year we. Full how way even the sigh. Extremely nor furniture fat questions now provision incommode preserved. Our side fail find like now. Discovered travelling for insensible partiality unpleasing impossible she. Sudden up my excuse to suffer ladies though or. Bachelor possible marianne directly confined relation as on he.
Unpacked reserved sir offering bed judgment may and quitting speaking. Is do be improved raptures offering required in replying raillery. Stairs ladies friend by in mutual an no. Mr hence chief he cause. Whole no doors on hoped. Mile tell if help they ye full name.
Cultivated who resolution connection motionless did occasional. Journey promise if it colonel. Can all mirth abode nor hills added. Them men does for body pure. Far end not horses remain sister. Mr parish is to he answer roused piqued afford sussex. It abode words began enjoy years no do no. Tried spoil as heart visit blush or. Boy possible blessing sensible set but margaret interest. Off tears are day blind smile alone had.
Spot of come to ever hand as lady meet on. Delicate contempt received two yet advanced. Gentleman as belonging he commanded believing dejection in by. On no am winding chicken so behaved. Its preserved sex enjoyment new way behaviour. Him yet devonshire celebrated especially. Unfeeling one provision are smallness resembled repulsive.
Entire any had depend and figure winter. Change stairs and men likely wisdom new
</div>
<div id='sticky-content'></div>
</div>
</div>
<div id="bottom">
</div>
假设视口不够高，我们需要一直滚动到底部才能看到紫色块（bottom div）。
我想要的是：
当我们从上到下滚动并且尚未显示紫色块时，透明块会粘到橙色块底部上方20px。已通过position: sticky完成。
当紫色块开始显示时，请阻止透明块向下移动，并将其保持在橙色块底部上方20像素的位置，就好像它是一个浮动按钮一样。由于粘性元素为positioned according to the normal flow of the document，因此失败。因此，在这种情况下，当紫色块完全显示时，透明块位于橙色块底部下方20px。
我想知道是否有任何方法可以实现两者。如果我们仅用CSS就能实现这一点，那就太好了。但是简单的JS代码也是首选。谢谢！
答案 0 :(得分：2)
一个想法是将粘性元素移动到容器的顶部而不是底部，并依靠负边距来避免正常的流动行为（当它在顶部时，然后在到达容器的底部时停止）。
检查以下评论以更好地理解。唯一的缺点是需要根据元素的高度手动设置一些值。您还将注意到顶部的值，也需要根据屏幕大小手动设置顶部的值，以模拟底部棒的行为。
#root-container {
display: flex;
}
#container1 {
width: 100px;
height: 500px;
background-color: grey;
}
#sticky-container {
width: 320px;
max-height: 500px;
position: relative;
background-color: lightgrey;
}
#sticky-container-header {
width: 320px;
height: 100px;
background-color: #2f4d92;
}
#full-height-content {
width: 100%;
height: 400px;
overflow-y: scroll;
background-color: #d67e23;
margin-top:-20px; /*same as the margin-bottom*/
}
#sticky-content {
width: 80%;
height: 100px;
margin-top:-100px; /*same as height*/
margin-bottom:20px; /*to avoid going under the bottom:20px we want*/
position: sticky;
top:calc(100vh - 100px - 20px);
background-color: rgba(0,0,0,0.5);
}
#bottom {
width: 420px;
height: 100px;
background-color: purple;
}
body {
margin:0;
}<div id='root-container'>
<div id="container1"></div>
<div id="sticky-container">
<div id='sticky-container-header'></div>
<div id='sticky-content'></div>
<div id='full-height-content'>
Saw yet kindness too replying whatever marianne. Old sentiments resolution admiration unaffected its mrs literature. Behaviour new set existence dashwoods. It satisfied to mr commanded consisted disposing engrossed. Tall snug do of till on easy. Form not calm new fail.
His followed carriage proposal entrance directly had elegance. Greater for cottage gay parties natural. Remaining he furniture on he discourse suspected perpetual. Power dried her taken place day ought the. Four and our ham west miss. Education shameless who middleton agreement how. We in found world chief is at means weeks smile.
Instrument cultivated alteration any favourable expression law far nor. Both new like tore but year. An from mean on with when sing pain. Oh to as principles devonshire companions unsatiable an delightful. The ourselves suffering the sincerity. Inhabit her manners adapted age certain. Debating offended at branched striking be subjects.
Must you with him from him her were more. In eldest be it result should remark vanity square. Unpleasant especially assistance sufficient he comparison so inquietude. Branch one shy edward stairs turned has law wonder horses. Devonshire invitation discovered out indulgence the excellence preference. Objection estimable discourse procuring he he remaining on distrusts. Simplicity affronting inquietude for now sympathize age. She meant new their sex could defer child. An lose at quit to life do dull.
Surrounded affronting favourable no mr. Lain knew like half she yet joy. Be than dull as seen very shot. Attachment ye so am travelling estimating projecting is. Off fat address attacks his besides. Suitable settling mr attended no doubtful feelings. Any over for say bore such sold five but hung.
Lose john poor same it case do year we. Full how way even the sigh. Extremely nor furniture fat questions now provision incommode preserved. Our side fail find like now. Discovered travelling for insensible partiality unpleasing impossible she. Sudden up my excuse to suffer ladies though or. Bachelor possible marianne directly confined relation as on he.
Unpacked reserved sir offering bed judgment may and quitting speaking. Is do be improved raptures offering required in replying raillery. Stairs ladies friend by in mutual an no. Mr hence chief he cause. Whole no doors on hoped. Mile tell if help they ye full name.
Cultivated who resolution connection motionless did occasional. Journey promise if it colonel. Can all mirth abode nor hills added. Them men does for body pure. Far end not horses remain sister. Mr parish is to he answer roused piqued afford sussex. It abode words began enjoy years no do no. Tried spoil as heart visit blush or. Boy possible blessing sensible set but margaret interest. Off tears are day blind smile alone had.
Spot of come to ever hand as lady meet on. Delicate contempt received two yet advanced. Gentleman as belonging he commanded believing dejection in by. On no am winding chicken so behaved. Its preserved sex enjoyment new way behaviour. Him yet devonshire celebrated especially. Unfeeling one provision are smallness resembled repulsive.
Entire any had depend and figure winter. Change stairs and men likely wisdom new
</div>
</div>
</div>
<div id="bottom">
</div>
答案 1 :(得分：0)
如果您希望避免出现负边距或处理高度可变的情况，那么CSS则无法使用。您的相对容器#sticky-container的内容#full-height-content的高度为400px。排名sticky不能同时起作用。您可以将其放置在其滚动祖先（文档）上，也可以通过在#sticky-container上设置溢出属性来将其放置在此处。
根据文档的正常流程定位元素，然后相对于其最近的滚动祖先和包含块（最近的块级祖先）偏移
如果您在overflow-y: hidden上设置了溢出属性（例如#sticky-container），则您的#sticky-content元素可能在文档中向下400px，而不是从底部20px视口（这就是您想要的）。
您似乎想让粘滞元素粘在视口上，然后在#sticky-container可见时以绝对方式“粘”在#bottom元素上。
通过使用JavaScript和IntersectionObserver，您可以同时使用两种方法。 #sticky-content会像您一样操作，直到#bottom进入视口。完成后，我们在.is-absolute上添加一个类（#sticky-content），将其放置在absolute而不是sticky的位置，然后它将位于20px的底部其相对父级#sticky-container（并且不再为其滚动祖先视口）。当#bottom离开视口时，IntersectionObserver将处理与此类相反的操作。
注意：：IntersectionObserver相当新，并且在所有主流浏览器中都not yet broadly supported。您可能对polyfill感到满意。
// The elements we want to control
var stickyContent = document.querySelector('#sticky-content');
var stickyContentActiveClass = 'is-absolute';
var bottom = document.querySelector('#bottom');
// The function to call when #bottom intersects with the viewport
var callback = function(entries, observer) {
entries.forEach(entry => {
if (entry.isIntersecting) {
stickyContent.classList.add(stickyContentActiveClass);
} else {
stickyContent.classList.remove(stickyContentActiveClass);
}
});
};
// Setting up the observer with an argument of 0 for the threshold
// Our callback function will run as soon as #bottom enters the viewport
var observer = new IntersectionObserver(callback, {threshold: 0});
// Tell our observer to watch #bottom
observer.observe(bottom);#root-container {
display: flex;
}
#container1 {
width: 100px;
height: 500px;
background-color: grey;
}
#sticky-container {
width: 320px;
max-height: 500px;
position: relative;
background-color: lightgrey;
}
#sticky-container-header {
width: 320px;
height: 100px;
background-color: #2f4d92;
}
#full-height-content {
width: 100%;
height: 400px;
overflow-y: scroll;
background-color: #d67e23;
}
#sticky-content {
width: 80%;
height: 100px;
position: sticky;
bottom: 20px;
background-color: rgba(0,0,0,0.5);
}
#sticky-content.is-absolute {
position: absolute;
}
#bottom {
width: 420px;
height: 100px;
background-color: purple;
}<div id='root-container'>
<div id="container1"></div>
<div id="sticky-container">
<div id='sticky-container-header'></div>
<div id='full-height-content'>
Saw yet kindness too replying whatever marianne. Old sentiments resolution admiration unaffected its mrs literature. Behaviour new set existence dashwoods. It satisfied to mr commanded consisted disposing engrossed. Tall snug do of till on easy. Form not calm new fail.
His followed carriage proposal entrance directly had elegance. Greater for cottage gay parties natural. Remaining he furniture on he discourse suspected perpetual. Power dried her taken place day ought the. Four and our ham west miss. Education shameless who middleton agreement how. We in found world chief is at means weeks smile.
Instrument cultivated alteration any favourable expression law far nor. Both new like tore but year. An from mean on with when sing pain. Oh to as principles devonshire companions unsatiable an delightful. The ourselves suffering the sincerity. Inhabit her manners adapted age certain. Debating offended at branched striking be subjects.
Must you with him from him her were more. In eldest be it result should remark vanity square. Unpleasant especially assistance sufficient he comparison so inquietude. Branch one shy edward stairs turned has law wonder horses. Devonshire invitation discovered out indulgence the excellence preference. Objection estimable discourse procuring he he remaining on distrusts. Simplicity affronting inquietude for now sympathize age. She meant new their sex could defer child. An lose at quit to life do dull.
Surrounded affronting favourable no mr. Lain knew like half she yet joy. Be than dull as seen very shot. Attachment ye so am travelling estimating projecting is. Off fat address attacks his besides. Suitable settling mr attended no doubtful feelings. Any over for say bore such sold five but hung.
Lose john poor same it case do year we. Full how way even the sigh. Extremely nor furniture fat questions now provision incommode preserved. Our side fail find like now. Discovered travelling for insensible partiality unpleasing impossible she. Sudden up my excuse to suffer ladies though or. Bachelor possible marianne directly confined relation as on he.
Unpacked reserved sir offering bed judgment may and quitting speaking. Is do be improved raptures offering required in replying raillery. Stairs ladies friend by in mutual an no. Mr hence chief he cause. Whole no doors on hoped. Mile tell if help they ye full name.
Cultivated who resolution connection motionless did occasional. Journey promise if it colonel. Can all mirth abode nor hills added. Them men does for body pure. Far end not horses remain sister. Mr parish is to he answer roused piqued afford sussex. It abode words began enjoy years no do no. Tried spoil as heart visit blush or. Boy possible blessing sensible set but margaret interest. Off tears are day blind smile alone had.
Spot of come to ever hand as lady meet on. Delicate contempt received two yet advanced. Gentleman as belonging he commanded believing dejection in by. On no am winding chicken so behaved. Its preserved sex enjoyment new way behaviour. Him yet devonshire celebrated especially. Unfeeling one provision are smallness resembled repulsive.
Entire any had depend and figure winter. Change stairs and men likely wisdom new
</div>
<div id='sticky-content'></div>
</div>
</div>
<div id="bottom">
</div>