Z-index无法处理固定标题和固定下拉菜单

Question

我正在尝试设计一个固定的下拉菜单,当我们正在通过较小的视图端口查看时,该菜单会滑动然后位于我的网站的固定标题下.我一定不能正确理解一些东西,因为尽管正确设置位置并且使用低于导航的父级的z-index ,它仍然无法正常工作.在下拉列表中,它会在我创建的菜单按钮下滑动,但是在标题上方,然后保持在标题上方.这是我的代码:

HTML:

<header>
    <div id="menu-button" class="up">menu</div>
    <nav role="primary" class="hide">
        <ul>
            <li><a href="#">foobar</a></li>
            <li><a href="#">foobar</a></li>
            <li><a href="#">foobar</a></li>
            <li><a href="#">foobar</a></li>
            <li><a href="#">foobar</a></li>
            <li><a href="#">foobar</a></li>
        </ul>
    </nav>
</header>

CSS:

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
}
header {
    display: block;
    float: left;
    width: 100%;
    height: 50px;
    background-color: hsla(0, 0%, 20%, 1);
    box-shadow: 0px 2px 8px #222;
    position: fixed;
    top: 0;
    z-index: 99;
}
#menu-button {
    display: block;
    float: left;
    background-color: hsla(0, 0%, 50%, 1);
    color: #fff;
    border: 2px solid #222;
    border-radius: 6px;
    padding: .25em .5em;
    margin-left: 10px;
    margin-top: 10px;
    cursor: pointer;
}
.up {
    background-image: linear-gradient(hsla(0, 0%, 100%, .2), hsla(0, 0%, 0%, .2));
}
.down {
    background-image: linear-gradient(hsla(0, 0%, 0%, .2), hsla(0, 0%, 100%, .2));
}
nav ul {
    list-style:none;
    width: 100%;
    position: fixed;
    z-index: -1;
    transition: all .6s ease;
    -webkit-transition: all .6s ease;
    -moz-transition: all .6s ease;
    -o-transition: all .6s ease;
}
.hide ul {
    top: -500px;
}
.reveal ul {
    top: 50px;
}
nav ul li a, nav ul li a:visited {
    display: block;
    float: left;
    width: 50%;
    background-color: hsla(0, 0%, 35%, 1);
    text-decoration: none;
    text-align: center;
    color: #fff;
    padding: 1em;
    border-right: 1px solid #fff;
    border-bottom: 1px solid #fff;
    transition: .4s all;
    -webkit-transition: .4s all;
    -moz-transition: .4s all;
    -o-transition: .4s all;
}
nav ul li:nth-child(even) a {
    border-right: none;
}
nav ul li:hover a {
    background-color: hsla(0, 0%, 50%, 1);
}

jQuery的:

$('#menu-button').click(function () {
    $(this).toggleClass('down');
    $('nav').toggleClass('reveal');
});

这是我为它制作的jsfiddle:

http://jsfiddle.net/kyleshevlin/yaJyK/6/

Answer 1

实现此目的并保持固定标头要求的一种方法是在菜单按钮周围添加一个包装器:

<div class='menu-wrap'>
    <div id="menu-button" class="up">menu</div>
</div>
<nav role="primary" class="hide">
    …
</nav>

将菜单包装为菜单栏的整个宽度/高度:

.menu-wrap {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: blue; /* just to make it obvious… */
}

演示小提琴