jquery - 中间有箭头的下拉菜单

Question

我正在尝试创建一个像这里那样的下拉菜单，但我没有成功地正确设计它的样式。

我要创建的菜单类似于找到的菜单 here

示例:

这就是我目前所拥有的!

http://jsfiddle.net/9ggfz0st/1/

@import url('http://getbootstrap.com/dist/css/bootstrap.css');
.dropdown-menu:before {
  position: absolute;
  top: -7px;
  left: 9px;
  display: inline-block;
  border-right: 7px solid transparent;
  border-bottom: 7px solid #ccc;
  border-left: 7px solid transparent;
  border-bottom-color: rgba(0, 0, 0, 0.2);
  content: '';
}
.dropdown-menu:after {
  position: absolute;
  top: -6px;
  left: 10px;
  display: inline-block;
  border-right: 6px solid transparent;
  border-bottom: 6px solid #ffffff;
  border-left: 6px solid transparent;
  content: '';
}

<div class="dropdown">
  <a data-toggle="dropdown" href="#">Dropdown trigger</a>
  <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel">
    Account Settings<hr>Billing
  </ul>
</div>

我无法将箭头居中到中间，还应用了“下拉菜单动画效果”

如何使箭头居中？

Answer 1

为了改变箭头的位置，只需像这样改变 left 的值:

.dropdown-menu:before {
  position: absolute;
  top: -7px;
  left: 40%;
  display: inline-block;
  border-right: 7px solid transparent;
  border-bottom: 7px solid #ccc;
  border-left: 7px solid transparent;
  border-bottom-color: rgba(0, 0, 0, 0.2);
  content: '';
}

.dropdown-menu:after {
  position: absolute;
  top: -6px;
  left: 40%;
  display: inline-block;
  border-right: 6px solid transparent;
  border-bottom: 6px solid #ffffff;
  border-left: 6px solid transparent;
  content: '';
}

JSFiddle