CSS下拉菜单转换

Question

我正在尝试为我正在处理的菜单添加下拉过渡,但似乎我不知道我做错了什么.菜单本身立即出现,忽略了过渡效果.

我用于过渡的CSS代码:

-webkit-transition: height 0.3s ease-in;
-moz-transition: height 0.3s ease-in;
-o-transition: height 0.3s ease-in;
-ms-transition: height 0.3s ease-in;
transition: height 0.3s ease-in;
opacity:0;

据我所知,我应该将它添加到nav ul ulCSS块,并添加opacity:1到nav ul li:hover > ul但它不起作用.

这是菜单的全部代码.

HTML

<nav>
    <ul>
        <li><a href="http://www.www.com/">Menu 1</a></li>
        <li><a href="http://www.www.com/">Menu 2</a></li>
        <li><a>Dropdown Here</a>
            <ul>
                <li><a href="http://www.www.com/">Dropdown1</a></li>
                <li><a href="http://www.www.com/">Dropdown2</a></li>
                <li><a href="http://www.www.com/">Dropdown3</a></li>
            </ul>
        </li>
        <li><a href="http://www.www.com/">Menu 4</a></li>
        <li><a href="http://www.www.com/">Menu 5</a></li>
    </ul>
</nav>

我正在使用的CSS

nav ul {
    background: #efefef; 
    background: linear-gradient(top, #efefef 0%, #bbbbbb 100%);  
    background: -moz-linear-gradient(top, #efefef 0%, #bbbbbb 100%); 
    background: -webkit-linear-gradient(top, #efefef 0%,#bbbbbb 100%); 
    box-shadow: 0px 0px 9px rgba(0,0,0,0.15);
    padding: 0 25px;
    border-radius: 10px;  
    list-style: none;
    position: relative;
    display: inline-table;
    float:right;
    z-index:9999;

}

nav ul ul {
    display: none;
    -webkit-transition: height 0.3s ease-in;
    -moz-transition: height 0.3s ease-in;
    -o-transition: height 0.3s ease-in;
    -ms-transition: height 0.3s ease-in;
    transition: height 0.3s ease-in;
    opacity:0;      
}

nav ul li:hover > ul {
    display: block;
    opacity:1;
}

nav ul:after {
    content: ""; 
    clear: both; 
    display: block;
}

nav ul li {
    float: left;
}

nav ul li:hover {
    background: #4b545f;
    background: linear-gradient(top, #4f5964 0%, #5f6975 40%);
    background: -moz-linear-gradient(top, #4f5964 0%, #5f6975 40%);
    background: -webkit-linear-gradient(top, #4f5964 0%,#5f6975 40%);
}

nav ul li:hover a {
    color: #fff;
}

nav ul li a {
    display: block;
    padding: 30px 20px;
    color: #757575; 
    text-decoration: none;
}

nav ul ul {
    background: #5f6975; 
    border-radius: 0px; 
    padding: 0;
    position: absolute; 
    top: 100%;
}

nav ul ul li {
    float: none; 
    border-top: 1px solid #6b727c;
    border-bottom: 1px solid #575f6a; 
    position: relative;
}

nav ul ul li a {
    padding: 15px 40px;
    color: #fff;
}   

nav ul ul li a:hover {
    background: #4b545f;
}

nav ul ul ul {
    position: absolute; left: 100%; top:0;
}

Answer 1

您的过渡不会触发,因为height您的元素不会在期间:hover,仅更改display和opacity.要使元素淡入 - 您需要将过渡属性更改为opacity或all.

如果要转换高度 - 需要将元素设置height为0,然后再将其更改:hover.

请注意 - 高度转换仅适用于指定height值,并且不适用于类似的值height: auto;.有一个解决方法,如下:

ul {
    transition: all 0.5s;
    max-height: 0;
}

ul:hover {
    max-height: 200px; //or whatever could be your max-height value - don't overdo it, will be crappy transition.
}