导航条根据窗口大小变化？

Question

我在我的整个文档中运行媒体查询，但这里我只想解释一下发生了什么。有没有可能让这个菜单保持中心，不管是什么设备？因此，当没有足够的空间允许所有菜单项停留在一行时，它会将其余的放在下面的行上，然后将那些放在屏幕上，而不是从左边开始新的行？这可能与我留在菜单上的浮子有关，但这是我唯一能让滚动条保持水平的方法。谢谢。

下面的HTML和CSS，但我建议在JSFiddle：https://jsfiddle.net/rt518s7p/上查看它

HTML：

<nav id="page-navigation">
      <ul>
            <li><a href="../../index.html" title="Home">Home</a></li>
                <ul class="top-menu">
                    <li><a href="../../_portfolio/photography.html" onclick="return false">Photography</a>
                    <ul class="sub-menu">
                        <li><a href="../../_portfolio/_photography/bmc-himley-mini-show-2015.html">BMC Himley Mini Show 2015</a></li>
                        <li><a href="../../_portfolio/_photography/kinver-snow.html">Kinver Snow</a></li>
                        <li><a href="../../_portfolio/_photography/mini-runs-collection.html">"Mini Runs" Collection</a></li>
                        <li><a href="../../_portfolio/_photography/hofner-bass.html">Hofner Bass</a></li>
                        <li><a href="../../_portfolio/_photography/nature.html">Nature</a></li>
                        <li><a href="../../_portfolio/_photography/haynes-motor-museum.html">Haynes Motor Museum</a></li>
                        <li><a href="../../_portfolio/_photography/miscellaneous.html">Miscellaneous</a></li>
                        <li><a href="../../_portfolio/_photography/classic-mini.html">Classic Mini</a></li>
                    </ul>
                </li>
                    <li><a href="../../_portfolio/graphic-design.html" onclick="return false">Graphic Design</a>
                    <ul class="sub-menu">
                        <li><a href="../../_portfolio/_graphic-design/story-bag-artwork.html">"Story Bag" Artwork</a></li>
                        <li><a href="../../_portfolio/_graphic-design/business-cards.html">Business Cards</a></li>
                        <li><a href="../../_portfolio/_graphic-design/logo-design.html">Logo Design</a></li>
                        <li><a href="../../_portfolio/_graphic-design/the-mexican-job.html">"The Mexican Job"</a></li>
                        <li><a href="../../_portfolio/_graphic-design/magazine-covers.html">Magazine Covers</a></li>
                        <li><a href="../../_portfolio/_graphic-design/wpap-artwork.html">WPAP Artwork</a></li>
                        <li><a href="../../_portfolio/_graphic-design/lyric-posters.html">Lyrics Posters</a></li>
                    </ul>
                </li>
                    <li><a href="../../_portfolio/3d-modelling.html">3D Modelling</a></li>
                </ul>
            <li><a href="../../about.html">About</a></li>
            <li><a href="../../recognition.html">Recognition</a></li>
      </ul>
  </nav>

CSS：

    /*navigation*/
#page-navigation
{
    width: 70%;
    height: 53px;
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 10px;
}

#page-navigation ul li
{
    color: white;
    list-style: none;
    background-color: darkslategray;
    width: 9em;
    float: left;
}

li
{
    position: relative;
}

li.title
{
    display: none;   
}

li a
{
    display: block;
    color: white;
    line-height: 1.3em;
    padding: 1em;
    text-align: center;
}

li a:link
{
    text-decoration: none;
}

li a:visited
{
    text-decoration: none;
    color: white;
}

li a:hover, .top-menu > li:hover > a
{
    background-color: rgb(48,48,48);
}

li a:active
{
    background-color: dimgray;
}

ul.sub-menu
{
    width: auto;
    height: auto;
    position: absolute;
    left: -9000em;
    overflow: hidden;
}

ul.sub-menu li
{
    clear: left;
    float: none;
    margin-left: -2.5em;
    z-index: 1000;
}

.top-menu li:hover ul
{
    left: 0;
}

ul.sub-menu li a
{
    height: auto;
    border-bottom: 1px solid gray;
    padding: .4em 1em;
    background-color: dimgray;
    padding-top: 1em;
    padding-bottom: 1em;
}

ul.sub-menu li:last-child a
{
    border-bottom: none;
}

ul.sub-menu li a:hover
{
    background-color: darkslategray;
}

ul.sub-menu li a:active
{
    background-color: gray;
}

ul.top-menu
{
    padding: 0;   
}

Answer 1

答案：

由于HTML文档的结构方式，您无法获得预期的效果，原因如下：

• 您有一个无序列表直接嵌套在另一个无序列表中，这是(1)不被认为是正确的(见此讨论)；但是更重要的是，尽管您的导航看起来有6个顶级项，但实际上只有4个。因此，无论您应用于它的CSS是什么，它都不会工作。

Recommendations:

1. 首先通过只在顶部导航项上使用适当的类并正确嵌套导航项来修复HTML文档的结构。
2. 我建议重组您的信息体系结构，以减少菜单上的导航项。例如，在您的About页面中进行识别将是有意义的。如果这是一个投资组合类型的网站，折叠你的摄影，平面设计，三维建模到项目中会很好。如果您关心的是分离，这将发生在页面中作为子导航。
3. 如果您打算保持导航结构，则建议将菜单折叠为选择菜单或移动设备上的汉堡包菜单，因为使用导航所消耗的大量移动设备屏幕对用户来说并不是一种好的体验。最重要的是，你必须考虑到用户不能在移动设备上“悬停”，这些下拉列表的大小充其量也是很难导航的。

*解决方案： 演示

HTML (固定)：

<nav id="page-navigation">
  <ul>
    <li><a href="../../index.html" title="Home">Home</a></li>
    <li class="top-menu"><a href="../../_portfolio/photography.html" onclick="return false">Photography</a>
      <ul class="sub-menu">
        <li><a href="../../_portfolio/_photography/bmc-himley-mini-show-2015.html">BMC Himley Mini Show 2015</a></li>
        <li><a href="../../_portfolio/_photography/kinver-snow.html">Kinver Snow</a></li>
        <li><a href="../../_portfolio/_photography/mini-runs-collection.html">"Mini Runs" Collection</a></li>
        <li><a href="../../_portfolio/_photography/hofner-bass.html">Hofner Bass</a></li>
        <li><a href="../../_portfolio/_photography/nature.html">Nature</a></li>
        <li><a href="../../_portfolio/_photography/haynes-motor-museum.html">Haynes Motor Museum</a></li>
        <li><a href="../../_portfolio/_photography/miscellaneous.html">Miscellaneous</a></li>
        <li><a href="../../_portfolio/_photography/classic-mini.html">Classic Mini</a></li>
      </ul>
    </li>
    <li class="top-menu"><a href="../../_portfolio/graphic-design.html" onclick="return false">Graphic Design</a>
      <ul class="sub-menu">
        <li><a href="../../_portfolio/_graphic-design/story-bag-artwork.html">"Story Bag" Artwork</a></li>
        <li><a href="../../_portfolio/_graphic-design/business-cards.html">Business Cards</a></li>
        <li><a href="../../_portfolio/_graphic-design/logo-design.html">Logo Design</a></li>
        <li><a href="../../_portfolio/_graphic-design/the-mexican-job.html">"The Mexican Job"</a></li>
        <li><a href="../../_portfolio/_graphic-design/magazine-covers.html">Magazine Covers</a></li>
        <li><a href="../../_portfolio/_graphic-design/wpap-artwork.html">WPAP Artwork</a></li>
        <li><a href="../../_portfolio/_graphic-design/lyric-posters.html">Lyrics Posters</a></li>
      </ul>
    </li>
    <li><a href="../../_portfolio/3d-modelling.html">3D Modelling</a></li>
    <li><a href="../../about.html">About</a></li>
    <li><a href="../../recognition.html">Recognition</a></li>
  </ul>
</nav>

CSS (固定和更新)：

/*navigation*/

#page-navigation {
  width: 100%;
  margin-left: auto;
  margin-right: auto;
  margin-bottom: 10px;
}

#page-navigation ul {
  text-align: center;
}

#page-navigation ul li {
  color: white;
  list-style: none;
  background-color: darkslategray;
  width: 9em;
  /* float: left removes any possibility of it centering */
  display: inline-block;
}

li {
  position: relative;
}

li.title {
  display: none;
}

li a {
  display: block;
  color: white;
  line-height: 1.3em;
  padding: 1em;
  text-align: center;
}

li a:link {
  text-decoration: none;
}

li a:visited {
  text-decoration: none;
  color: white;
}

li a:hover,
.top-menu > li:hover > a {
  background-color: rgb(48, 48, 48);
}

li a:active {
  background-color: dimgray;
}

ul.sub-menu {
  width: auto;
  height: auto;
  position: absolute;
  left: -9000em;
  overflow: hidden;
}

ul.sub-menu li {
  clear: left;
  float: none;
  margin-left: -2.5em;
  z-index: 1000;
}

.top-menu:hover ul {
  left: 0;
}

ul.sub-menu li a {
  height: auto;
  border-bottom: 1px solid gray;
  padding: .4em 1em;
  background-color: dimgray;
  padding-top: 1em;
  padding-bottom: 1em;
}

ul.sub-menu li:last-child a {
  border-bottom: none;
}

ul.sub-menu li a:hover {
  background-color: darkslategray;
}

ul.sub-menu li a:active {
  background-color: gray;
}

ul.top-menu {
  padding: 0;
}

仍然有一些小风格需要调整，但这应该能让你根据你的问题得到你想要的东西。