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。这是一些代码：

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，就像您添加的那样 :after

#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，请查看

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

使用前后 class 可以轻松完成。将伪元素更改为 before，然后使用 after 伪元素在黑色 trainagle 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;

}

使用 CSS 在导航栏中显示边框三角形

Show border triangle in navbar using CSS

html

css

css-shapes