悬停在css上的菜单项样式

Question

如何创建如下所示的菜单效果

目前，我的应用程序菜单如下所示，

HTML：

<nav id="nav">
     <ul id="navigation">
     <li><a href="#" class="first">Reports</a></li>
     <li><a href="#">Analytics</a></li>
     <li><a href="#">Dashboards</a></li>
      <li><a href="#">Monitors &raquo;</a>
      <ul>
      <li><a href="#">Real time</a></li>
      <li><a href="#">Real time monitoring</a></li>
     </ul>
     </li>
     </ul>
</nav>

这是我对李的css，

#nav {
    display: inline;
    position:relative;
    margin:0;
    padding:0px;
}

ul#navigation {
    position:relative;
    float:left;
    border-left:0px solid #c4dbe7;
    list-style-type: none;
    margin: 0px;
    padding: 0px;
    border-right:0px solid #c4dbe7;
}

ul#navigation li {
    display:inline;
    font-size:12px;
    font-weight:bold;
    margin:0;
    padding:0;
    float:left;
    position:relative;
    border-top:0px solid #c4dbe7;
    border-bottom:0px solid #c4dbe7;
}

ul#navigation li a {
    padding:15px 15px;
    color:#858585;
    /*text-shadow:1px 1px 0px #fff;*/
    text-decoration:none;
    display:inline-block;
    border-right:0px solid #fff;
    border-left:0px solid #C2C2C2;
    border-top:0px solid #fff;


    -webkit-transition:color 0.2s linear, background 0.2s linear;
    -moz-transition:color 0.2s linear, background 0.2s linear;
    -o-transition:color 0.2s linear, background 0.2s linear;
    transition:color 0.2s linear, background 0.2s linear;
}

ul#navigation li a:hover {
    background:#df191a;
    color:#282828;
}

ul#navigation li a.first {
    border-left: 0 none;
}

ul#navigation li a.last {
    border-right: 0 none;
}

ul#navigation li:hover > a {
    background:#df191a;
}

/* Drop-Down Navigation */
ul#navigation li:hover > ul
{
    /*these 2 styles are very important,
    being the ones which make the drop-down to appear on hover */
    visibility:visible;
    opacity:1;
}

ul#navigation ul, ul#navigation ul li ul {
    list-style: none;
    margin: 0;
    padding: 0;
    /*the next 2 styles are very important,
    being the ones which make the drop-down to stay hidden */
    visibility:hidden;
    opacity:0;
    position: absolute;
    z-index: 99999;
    width:180px;
    background:#f8f8f8;
    box-shadow:1px 1px 3px #ccc;
    /* css3 transitions for smooth hover effect */
    -webkit-transition:opacity 0.2s linear, visibility 0.2s linear;
    -moz-transition:opacity 0.2s linear, visibility 0.2s linear;
    -o-transition:opacity 0.2s linear, visibility 0.2s linear;
    transition:opacity 0.2s linear, visibility 0.2s linear;
}

ul#navigation ul {
    top: 47px;
    left: 0px;
}

ul#navigation ul li ul {
    top: 0;
    left: 181px; /* strong related to width:180px; from above */
}

ul#navigation ul li {
    clear:both;
    width:100%;
    border:0 none;
    border-bottom:1px solid #c9c9c9;
}

Answer 1

在任何子菜单的第一个li上使用边框技术制作的伪元素“三角形”似乎就是答案。

* {
    margin: 0;
    padding: 0;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}
a {
    color:white;
    text-decoration: none;
}
ul#navigation li {
    display: inline-block;
    background: #ccc;
    vertical-align: top;
    position: relative;
}
ul#navigation > li > ul {
    position: absolute;
    top:100%;
    left:0;
    display: none;
}
ul#navigation > li:hover > ul {
    display: block;
}
ul#navigation > li > ul > li {
    width:100%;
    position: relative;
    background: white;
    color:grey;
    border-bottom: 1px solid grey;
}

ul#navigation > li > ul > li:first-child:before {
    position: absolute;
    content:"";
    bottom:100%;
    left:25%;
    transform:translateX(-50%);
    border: solid transparent;
    content:" ";
    height: 0;
    width: 0;
    border-bottom-color: white;
    border-width: 12px;
}
ul#navigation li a {
    display: block;
    height: 0 1rem;
    line-height: 25px;
    padding: 0.5rem;
}

ul#navigation > li > ul > li a {
    color: grey;
    white-space:nowrap;
}

<nav id="nav">
    <ul id="navigation">
        <li><a href="#" class="first">Reports</a>

        </li>
        <li><a href="#">Analytics</a>

            <ul>
                <li><a href="#">Real time</a>

                </li>
                <li><a href="#">Real time monitoring</a>

                </li>
            </ul>
        </li>
        <li><a href="#">Dashboards</a>

        </li>
        <li><a href="#">Monitors &raquo;</a>

            <ul>
                <li><a href="#">Real time</a>

                </li>
                <li><a href="#">Real time monitoring</a>

                </li>
            </ul>
        </li>
    </ul>
</nav>

Answer 2

我不知道你的整个代码，但是，它是这样的：

ul#navigation:before {
    bottom: 100%;
    left: 50%;
    border: solid transparent;
    content: " ";
    height: 0;
    width: 0;
    position: absolute;
    pointer-events: none;
    border-color: rgba(136, 183, 213, 0);
    border-bottom-color: #cbcbcb;
    border-width: 12px;
    margin-left: -12px;
}

您只需要在菜单上定位三角形......