javascript - 下拉菜单淡出

Question

我创建了一个下拉菜单。当用户将鼠标悬停在导航按钮上时，使用 CSS3 Transitions 类“下拉内容”淡入，如下面的演示所示:

https://jsfiddle.net/4xk78qse/

我想不通的是当用户没有将鼠标悬停在任何按钮上时如何淡出“下拉内容”。

我试过添加

animation fadeout 2s;

@keyframes fadeout {
   from { opacity: 1; }
   to { opacity: 0; }
}

本质上与 jsfiddle 示例中的动画淡入淡出相反，但这没有用。

总而言之，当用户没有将鼠标悬停在任何按钮上时，我希望淡出。

Answer 1

这里的技巧是使用 CSS Transitions而不是 CSS 动画。您将设置 visibility 和 opacity 而不是显示。

.dropdown-content {
    visibility: hidden;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    -webkit-transition: opacity 2s, visibility 2s;
    -moz-transition: opacity 2s, visibility 2s;
    -ms-transition: opacity 2s, visibility 2s;
    -o-transition: opacity 2s, visibility 2s;
    transition: opacity 2s, visibility 2s;
    opacity: 0;
}
.dropdown:hover .dropdown-content {
    visibility: visible;
    opacity: 1;
}

这是您要完成的工作演示:

.dropbtn {
    background-color: #222222;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
    height: 80px;
    font-family: 'Quicksand', sans-serif;
}

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

.dropdown-content {
    visibility: hidden;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    -webkit-transition: opacity 2s, visibility 2s;
    -moz-transition: opacity 2s, visibility 2s;
    -ms-transition: opacity 2s, visibility 2s;
    -o-transition: opacity 2s, visibility 2s;
    transition: opacity 2s, visibility 2s;
    opacity: 0;
}

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
    font-family: 'Quicksand', sans-serif;
}

.dropdown-content a:hover {background-color: #2c2c2c; color: #FFF;}

.dropdown:hover .dropdown-content {
    visibility: visible;
    opacity: 1;
}

.dropdown:hover .dropbtn {
    background-color: #2c2c2c;
}

<div class="dropdown">
  <button class="dropbtn">Navigation</button>
  <div class="dropdown-content">
    <a href="index.html">1</a>
    <a href="slimedash.html">2</a>
    <a href="gmod.html">3</a>
    <a href="minecraft.html">4</a>
    <a href="information.html">5</a>
    <a href="contact.html">6</a>
  </div>
</div>