CSS下拉过渡

Question

关于如何使用CSS动画我的下拉菜单，我有点迷失方向。你们这些人能把我点燃吗？

我试过了

  -webkit-transition: all 0.3s ease;
  -moz-transition: all 0.3s ease;
  -ms-transition: all 0.3s ease;
  -o-transition: all 0.3s ease;
  transition: all 0.3s ease;   

但是我不知道如何准确地做到这一点。子菜单显示但立即没有任何转换。任何帮助都会很棒。

.dropbtn {
  background-color: inherit;
  color: inherit;
  padding: inherit;
  font-size: inherit;
}

.dropdown {
  position: relative;
  display: inline-block;
  font-size: inherit;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: white;
  min-width: 150px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  -webkit-transition: all 0.3s ease;
  -moz-transition: all 0.3s ease;
  -ms-transition: all 0.3s ease;
  -o-transition: all 0.3s ease;
  transition: all 0.3s ease;
  height: 100px;     
}

.dropdown-content a {
  color: black;
  padding: 12px 12px;
  text-decoration: none;
  display: block;
  background-color: white;
}

.dropdown:hover .dropdown-content {
  display: block;
  height: 200px;
}

<ul>
  <li class="dropdown">
    <a href="javascript:" class="dropbtn">Dropdown</a>
    <div class="dropdown-content">
      <a href="#">Menu 1</a>
      <a href="#">Menu 2</a>
      <a href="#">Menu 3</a>
    </div>
  </li> 
</ul>

Answer 1

display属性不能动画，因为它既可以是一个值，也可以不是，它们之间没有任何内容。您更愿意转换元素的opacity属性，默认情况下将其设置为0，并在悬停时将其设置为1，删除display: none;。除此之外，使用pointer-events: none防止不可见的.dropdown-content元素拦截任何鼠标事件，如悬停或点击，并在父元素悬停时将其设置为pointer-events: all。

.dropbtn {
  background-color: inherit;
  color: inherit;
  padding: inherit;
  font-size: inherit;
}

.dropdown {
  position: relative;
  display: inline-block;
  font-size: inherit;
}

.dropdown-content {
  opacity: 0;
  pointer-events: none;
  position: absolute;
  background-color: white;
  min-width: 150px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  -webkit-transition: all 0.3s ease;
  -moz-transition: all 0.3s ease;
  -ms-transition: all 0.3s ease;
  -o-transition: all 0.3s ease;
  transition: all 0.3s ease;
  height: 100px;     
}

.dropdown-content a {
  color: black;
  padding: 12px 12px;
  text-decoration: none;
  display: block;
  background-color: white;
}

.dropdown:hover .dropdown-content {
  opacity: 1;
  height: 200px;
  pointer-events: all;
}

<ul>
 <li class="dropdown">
      <a href="javascript:" class="dropbtn">Dropdown</a>
           <div class="dropdown-content">
               <a href="#">Menu 1</a>
               <a href="#">Menu 2</a>
               <a href="#">Menu 3</a>
          </div>
  </li>
</ul>