使用 CSS 在导航栏中显示边框三角形

Question

我正在尝试在悬停的项目下方创建一个带有箭头的导航栏。这是我想要做的：

对于箭头，我使用了伪元素before 和after。以下是部分代码：

body {
  background: #FFFFFF;
  color: #FFFFFF;
  margin: 0px;
  padding: 0px;
  height: 100%;
}
.clear {
  clear: both;
}
.page-wrap {
  width: 980px;
  margin: 0px auto;
  height: 100%;
}
#main-menu {
  background: white;
  height: 55px;
  width: 100%;
  padding: 0px;
  margin: 0px;
  border-bottom: 1px solid black;
}
ul {
  font-family: Arial, Verdana;
  font-size: 18px;
  margin: 0;
  padding: 0;
  list-style: none;
}
ul li {
  display: block;
  position: relative;
  float: left;
}
li ul {
  display: none;
}
ul li a {
  display: block;
  text-decoration: none;
  color: black;
  padding: 0 9px 0 9px;
  background: white;
  margin-left: 1px;
  white-space: nowrap;
  line-height: 55px;
  font: 18px;
  font-family: Arial, Helvetica, sans-serif;
  outline: none;
}
ul li a:hover {
  color: black;
}
#menu a:hover:after {
  content: "";
  position: absolute;
  top: 40px;
  left: 50%;
  margin-left: -15px;
  width: 0px;
  height 0px;
  xxmargin: 0px auto;
  border-left: 15px solid transparent;
  border-right: 15px solid transparent;
  border-bottom: 15px solid black;
}

<header id="main-menu">
  <div class="page-wrap">
    <ul id="menu">
      <li><a href="#">Recommended</a></li>
      <li><a href="#">Recent</a></li>
    </ul>
  </div>
</header>

Fiddle Link

由于边框颜色，箭头是黑色的。如何只显示箭头的边框？

Answer 1

只需添加 before 伪元素就像您添加 :after 一样

#menu a:hover:after {
  content: "";
  position: absolute;
  top: 41px;
  left: 50%;
  margin-left: -15px;
  width: 0px;
  height 0px;
  margin: 0px auto;
  border-left: 15px solid transparent;
  border-right: 15px solid transparent;
  border-bottom: 15px solid white;
}
#menu a:hover:before {
  content: "";
  position: absolute;
  top: 40px;
  left: 50%;
  margin-left: -15px;
  width: 0px;
  height 0px;
  margin: 0px auto;
  border-left: 15px solid transparent;
  border-right: 15px solid transparent;
  border-bottom: 15px solid black;
}

我已经更新了你的笔，请检查

http://codepen.io/anon/pen/vOxmGZ

Answer 2

您可以使用带边框的旋转伪元素：

body {
  background: #FFFFFF;
  color: #FFFFFF;
  margin: 0px;
  padding: 0px;
  height: 100%;
}
.page-wrap {
  width: 980px;
  margin: 0px auto;
  height: 100%;
}
#main-menu {
  background: white;
  height: 55px;
  width: 100%;
  padding: 0px;
  margin: 0px;
  border-bottom: 1px solid black;
}
ul {
  font-family: Arial, Verdana;
  font-size: 18px;
  margin: 0;
  padding: 0;
  list-style: none;
}
ul li {
  display: block;
  position: relative;
  float: left;
}
li ul {
  display: none;
}
ul li a {
  display: block;
  text-decoration: none;
  color: black;
  padding: 0 9px 0 9px;
  background: white;
  margin-left: 1px;
  white-space: nowrap;
  line-height: 55px;
  font: 18px;
  font-family: Arial, Helvetica, sans-serif;
  outline: none;
}
ul li a:hover {
  color: black;
}
#menu a:hover:after {
  content: "";
  position: absolute;
  bottom:-10px;
  left: 50%;
  margin-left:-10px;
  width: 20px;
  height: 20px;
  background:#fff;
  -webkit-transform:rotate(45deg);
  -ms-transform:rotate(45deg);
  transform:rotate(45deg);
  border-left:1px solid #000;
  border-top:1px solid #000;
  box-sizing:border-box;
}

<header id="main-menu">
  <div class="page-wrap">
    <ul id="menu">
      <li><a href="#">Recommended</a>
      </li>

      <li><a href="#">Recent</a>
      </li>
    </ul>
  </div>
</header>

Answer 3

使用课前课和课后课可以轻松完成。将您的伪元素更改为之前和之后使用伪元素在黑色火车头内绘制一个白色三角形。 对于您的代码，css 可以是这样的

#menu a:hover:before {
    content: "";
    position: absolute;
    top: 40px;
    left: 50%;
    margin-left: -15px;
    width: 0px;
    height 0px;
    xxmargin: 0px auto;
    border-left: 15px solid transparent;
    border-right: 15px solid transparent;
    border-bottom: 15px solid black;

    }
#menu a:hover:after {
    content: "";
    position: absolute;
    top: 40px;
    left: 50%;
    margin-left: -15px;
    width: 0px;
    height 0px;
    xxmargin: 0px auto;
    border-left: 12px solid transparent;
    border-right: 12px solid transparent;
    border-bottom: 12px solid white;

}