根据 parent 高度动态对齐伪元素

Question

我正在尝试创建一个箭头标签，使用 css :after

.one-line {
  font-size: 2em;
  width: 150px;
  min-height: 50px;
  height: auto;
  background: blue;
  margin: 5px;
  position: relative;
  color: #fff;
}

.one-line:after {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  left: 100%;
  width: 0;
  height: 0;
  border-top: 25px solid transparent;
  border-bottom: 25px solid transparent;
  border-left: 25px solid red;
}

<div class="one-line">text<br>text<br></div>

我想让after元素的高度和parent一样高，我怎么用css或者js实现呢？

注意：标签内的文本是动态填充的。 [文本最大长度：2行]

如我所想，可能无法将其调整到 parent 的任何高度。目前我正在尝试调整一行和两行文本。

Answer 1

好吧，您可以选择保持箭头大小相同并将其居中对齐，方法是将顶部更改为 top: 50%; 并添加 transform: translateY(-50%);

.one-line{
  
  width: 150px;
  min-height: 50px;
  height: auto;
  background: blue;
  margin: 5px;
  position: relative;
  color: #fff;
  
}

.one-line:after{
  content: '';
  display: block;
  position: absolute;
  left: 100%;
  width: 0; 
  height: 0; 
  border-top: 25px solid transparent;
  border-bottom: 25px solid transparent;
  border-left: 25px solid red;
  
  top: 50%;
  transform: translateY(-50%);
}

<div class="one-line">text<br>text<br>text<br>text</div>

<div class="one-line">text<br>text<br>text<br>text<br>text<br>text<br>text<br>text<br>text<br>text<br>text</div>

Answer 2

这是一个使用 clip-path 的解决方案。这个想法是在多边形中使用 % 值来仅显示所需的形状，并且无论高度是多少，它都将始终有效：

.one-line {
  font-size: 2em;
  width: 150px;
  min-height: 50px;
  height: auto;
  background: blue;
  margin: 5px;
  position: relative;
  color: #fff;
}

.one-line:after {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  bottom: 0;
  width: 25px;
  right: -25px;
  background: red;
  -webkit-clip-path: polygon(100% 50%, 0 0, 0 100%);
  clip-path: polygon(100% 50%, 0 0, 0 100%);
}

<div class="one-line">text<br>text<br></div>
<div class="one-line">text<br>text<br>text<br></div>

<div class="one-line">text</div>

<div class="one-line">text<br>text<br>text<br>text<br>text<br>text<br>text<br></div>

这是另一种解决方案，它依赖于伪元素和一些 skew 转换来创建箭头。你会注意到这个会保持箭头的比例。

.one-line {
  font-size: 2em;
  width: 150px;
  min-height: 50px;
  height: auto;
  background: blue;
  margin: 5px;
  position: relative;
  color: #fff;
}

.one-line:after {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  height: 50%;
  width: 50%;
  right: -25px;
  background: red;
  transform: skewX(20deg) translateX(-33%);
  transform-origin: top;
  z-index: -1;
}

.one-line:before {
  content: '';
  display: block;
  position: absolute;
  bottom: 0;
  height: 50%;
  width: 50%;
  right: -25px;
  background: red;
  transform: skewX(-20deg) translateX(-33%);
  transform-origin: bottom;
  z-index: -1;
}

<div class="one-line">text<br>text<br></div>
<div class="one-line">text<br>text<br>text<br></div>

<div class="one-line">text</div>

<div class="one-line">text<br>text<br>text<br>text<br>text<br>text<br>text<br></div>

另一种方式只有一个伪元素和linear-gradient.

.one-line {
  font-size: 2em;
  width: 150px;
  min-height: 50px;
  height: auto;
  background: blue;
  margin: 5px;
  position: relative;
  color: #fff;
}

.one-line:after {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  height: 100%;
  width: 50px;
  right: -50px;
  background: 
   linear-gradient(to bottom left, transparent 49.4%, red 50%) top, 
   linear-gradient(to top left,    transparent 49.4%, red 50%) bottom;
  background-size:100% 50.2%;
  background-repeat:no-repeat;
}

<div class="one-line">text<br>text<br></div>
<div class="one-line">text<br>text<br>text<br></div>

<div class="one-line">text</div>

<div class="one-line">text<br>text<br>text<br>text<br>text<br>text<br>text<br></div>

最后没有任何伪元素，主元素只有背景：

.one-line {
  font-size: 2em;
  width: 200px;
  padding-left:50px;
  min-height: 50px;
  height: auto;
  background: 
   linear-gradient(blue,blue) left/calc(100% - 50px) 100%,
   linear-gradient(to bottom left, transparent 49.4%, red 50%) top right/50px 50.2%, 
   linear-gradient(to top left, transparent 49.4%, red 50%) bottom right/50px 50.2%;
  background-repeat:no-repeat;
  margin: 5px;
  position: relative;
  color: #fff;
}

<div class="one-line">text<br>text<br></div>
<div class="one-line">text<br>text<br>text<br></div>

<div class="one-line">text</div>

<div class="one-line">text<br>text<br>text<br>text<br>text<br>text<br>text<br></div>

Answer 3

使用 svg 路径作为 background-image，您可以将 background-size 属性拉伸到 100% 100%。只要确保 svg 有 preserveAspectRatio="none"

.one-line:after {
    background-image: url('data:image/svg+xml;charset=UTF-8,<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" preserveAspectRatio="none" viewBox="0 0 25.1 50" style="enable-background:new 0 0 25.1 50;" xml:space="preserve"><polygon class="st0" points="0,50 0,50 25,25 0,0" fill="#ff0000"/></svg>');
    position: absolute;
    top: 0;
    left:100%;
    height: 100%;
   width: 25px;
    background-size: 100% 100%;
    background-repeat:no-repeat;
    display: block;
    content:'';
}

https://jsfiddle.net/7jm54u6L/

根据 parent 高度动态对齐伪元素

Dynamically aligning pseudo element according to parent height

html

css

css-shapes