CSS过渡自动高度不起作用[重复]

Question

我有一个网站，我决定用纯 CSS sn-ps 替换基于 jquery 的切换框。当我为过渡使用固定高度值（CSS的最后几行）时，效果很好，但是使用auto值时，动画丢失了，只有高度变化有效果！

有没有办法将它与自动值一起使用？我想使用可变文本而不是脚本。

.ac-container{
  width: 400px;
  margin: 10px auto 30px auto;
  text-align: left;
}
.ac-container label{
  font-family: 'BebasNeueRegular', 'Arial Narrow', Arial, sans-serif;
  padding: 5px 20px;
  position: relative;
  z-index: 20;
  display: block;
  height: 30px;
  cursor: pointer;
  color: #777;
  text-shadow: 1px 1px 1px rgba(255,255,255,0.8);
  line-height: 33px;
  font-size: 19px;
  background: #ffffff;
  background: -moz-linear-gradient(top, #ffffff 1%, #eaeaea 100%);
  background: -webkit-gradient(linear, left top, left bottom, color-stop(1%,#ffffff), color-stop(100%,#eaeaea));
  background: -webkit-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
  background: -o-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
  background: -ms-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
  background: linear-gradient(top, #ffffff 1%,#eaeaea 100%);
  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#eaeaea',GradientType=0 );
  box-shadow: 
    0px 0px 0px 1px rgba(155,155,155,0.3), 
    1px 0px 0px 0px rgba(255,255,255,0.9) inset, 
    0px 2px 2px rgba(0,0,0,0.1);
}
.ac-container label:hover{
  background: #fff;
}
.ac-container input:checked + label,
.ac-container input:checked + label:hover{
  background: #c6e1ec;
  color: #3d7489;
  text-shadow: 0px 1px 1px rgba(255,255,255, 0.6);
  box-shadow: 
    0px 0px 0px 1px rgba(155,155,155,0.3), 
    0px 2px 2px rgba(0,0,0,0.1);
}

.ac-container input{
  display: none;
}
.ac-container section{
  background: rgba(255, 255, 255, 0.5);
  margin-top: -1px;
  overflow: hidden;
  height: 0px;
  position: relative;
  z-index: 10;
  -webkit-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
  -moz-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
  -o-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
  -ms-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
  transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
}
.ac-container section p{
  font-style: italic;
  color: #777;
  line-height: 23px;
  font-size: 14px;
  padding: 20px;
  text-shadow: 1px 1px 1px rgba(255,255,255,0.8);
}
.ac-container input:checked ~ section{
  -webkit-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
  -moz-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
  -o-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
  -ms-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
  transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
  box-shadow: 0px 0px 0px 1px rgba(155,155,155,0.3);
}
.ac-container input:checked ~ section.ac-small{
  height: 120px; /*auto*/
}

<div class="ac-container">
  <div>

    <input id="ac-1" name="accordion-1" type="checkbox" />
    <section class="ac-small">
      <p>Some content... </p>
    </section>
    <label for="ac-1">About us</label>

  </div>	

  <div>	
    <input id="ac-2" name="accordion-2" type="checkbox" />
    <section class="ac-small">
      <p>Some content... </p>
    </section>
    <label for="ac-2">About us</label>
  </div>
</div>

Answer 1

CSS 过渡不适用于自动值。使用 JavaScript el.scrollHeight 获取滚动高度或使用 max-height 代替。

Answer 2

auto 不是动画属性的合适类型，请参阅CSS Transitions: 7. Animatable properties。您需要长度 (px,em,...) 或百分比 (13.37%)。

因此，只要不将auto 添加到列表中，就不可能使用纯 CSS 的解决方案。您需要使用 JavaScript 或特定的长度值。