css – 在bootstrap中为下划线激活的导航栏链接4

我正在将一个网站从bootstrap 3升级到4(测试版).我用来强调活动导航栏链接的CSS不再有效.它不是强调项目的下划线,而是强调页面的整个宽度.如何在bootstrap 4中为活动导航项加下划线？

Bootstrap 3 css

.navbar-default .navbar-nav > .active:after {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    content: " ";
    border-bottom: 5px solid #5BC0EB;
}

尝试Bootstrap 4 css

.navbar-light .navbar-nav .active::after {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    content: " ";
    border-bottom: 5px solid #5BC0EB;
}

HTML

<nav class="navbar fixed-top navbar-light bg-light navbar-expand-md">
    <div class="container">
        <a class="navbar-brand" href="#">My Website</a>

        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarCollapse" aria-controls="navbarCollapse"
            aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
        </button>

        <div class="collapse navbar-collapse justify-content-end" id="main-nav-collapse">
            <ul class="navbar-nav">
                <li class="nav-item active"><a class="nav-link" href="#about">About</a></li>
                <li class="nav-item"><a class="nav-link" href="#classes">Classes</a></li>
                <li class="nav-item"><a class="nav-link" href="#gallery">gallery</a></li>
                <li class="nav-item"><a class="nav-link" href="#events">Events</a></li>
                <li class="nav-item"><a class="nav-link" href="#contact">Contact</a></li>
                <li class="nav-item"><a class="nav-link" href="#offers">Offers</a></li>
            </ul>
        </div>
    </div>
</nav>

解决方法

这是因为你的定位.

尝试设置你的li的相对位置,然后设置li里面的标签,它将绝对定​​位如下

.navbar-nav > li {
  float: left;
  position: relative;
}
.navbar-light .navbar-nav .active a::after {
  border-bottom: 5px solid #5bc0eb;
  bottom: -10px;
  content: " ";
  left: 0;
  position: absolute;
  right: 0;
}

希望能帮助到你.