Bootstrap 4：在导航栏折叠时显示活动导航项
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【中文标题】Bootstrap 4：在导航栏折叠时显示活动导航项【英文标题】：Bootstrap 4: Show active nav-item on Navbar collapse 【发布时间】：2018-09-03 00:05:18 【问题描述】：我正在尝试使用在特定视口宽度处折叠的引导程序创建一个导航栏。现在，我想看到的是，如果导航栏折叠，navbar-brand 会消失，并且当前活动的导航项（例如“主页”、“关于”等）将在左侧可见，从而使访问者能够看看他们在哪一页。
我是一个完全的引导菜鸟，我有点希望在导航栏折叠/展开时看到要添加的 CSS 类，但它不会那样工作。
<html lang="en"><head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">Project name</a>
</div>
<div id="navbar" class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="#about">About</a></li>
<li><a href="#contact">Contact</a></li>
</ul>
</div><!--/.nav-collapse -->
</div>
</nav>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="../../assets/js/vendor/jquery.min.js"><\/script>')</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</body></html>【问题讨论】：
你必须使用 Bootstrap 3 吗？使用 Bootstrap 4 会更容易。而且，您想要在导航栏的折叠/切换部分中唯一的就是品牌？ 不行也可以使用 bootstrap 4 :) 这个想法是当brand + nav items变得太宽时，它会崩溃。然后品牌消失，导航项目可以用汉堡菜单打开。但在左侧（品牌曾经所在的位置）的折叠状态下，它应该显示“Home”（或：“About”、“Contact”等）。我有点希望这可以在没有太多 jquery 魔法的情况下开箱即用：/ 【参考方案1】：不完全是“开箱即用”，但一点 CSS 将适用于 Bootstrap 4（没有 jquery 或 dup 标记）...
https://www.codeply.com/go/5T4icATKjl
这会覆盖导航栏折叠行为以使用visibility 而不是display。这样我们就可以控制active nav-item 的显示。
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" ></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<style>
.navbar .collapse
visibility: hidden;
display: block;
.navbar .collapse.show
visibility: visible;
@media (max-width: 767px)
.navbar-nav .nav-link.active
visibility: visible;
.collapsing
transition: all 0.35s ease;
height: 40px !important;
.collapse:not(.show) .navbar-nav .nav-item:not(.active)
display: none;
@media (min-width: 768px)
.navbar .collapse .navbar-nav .nav-item
visibility: visible;
</style>
<body>
<nav class="navbar navbar-expand-md fixed-top navbar-dark bg-dark">
<div class="container">
<div class="collapse" id="navbar1">
<div class="navbar-nav flex-md-row">
<a class="nav-item navbar-brand" href="#">Project name</a>
<a class="nav-item nav-link" href="#">Home</a>
<a class="nav-item nav-link" href="#">About</a>
<a class="nav-item nav-link active" href="#">Contact</a>
</div>
</div>
<button class="navbar-toggler align-self-start" type="button" data-toggle="collapse" data-target="#navbar1">
<span class="navbar-toggler-icon"></span>
</button>
</div>
</nav>
</body>注意@media 查询与 768px 的 navbar-expand-md 断点一起出现。如果需要，您可以更改它以使用不同的断点。
navbar-expand-sm - 576pxnavbar-expand-lg - 992pxnavbar-expand-xl - 1200px
还有另一种使用重复导航栏导航链接的解决方案，但这需要额外的标记，我认为上面唯一的 CSS 解决方案更简洁。
【讨论】：
是的，这就是我所追求的！谢谢！【参考方案2】：无法直接在引导程序中使用，但您可以在此处编写一个小的 javascript 代码：
function displayActiveMenu()
if ($(window).width() >= 768)
// do nothing if we are not collapsed
return;
var element = $('li.active', '#navbar').clone();
$('#active-navbar').html(element);
displayActiveMenu(); // for the first time
$(window).on('resize', displayActiveMenu);@media (max-width: 767px)
#active-navbar
float: right;
margin: 0;
#active-navbar>li>a
padding-top: 15px;
padding-bottom: 15px;
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<!-- this is the new element -->
<ul class="nav navbar-nav visible-xs" id="active-navbar">
</ul>
<a class="navbar-brand" href="#">Project name</a>
</div>
<div id="navbar" class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="#about">About</a></li>
<li><a href="#contact">Contact</a></li>
</ul>
</div>
<!--/.nav-collapse -->
</div>
</nav>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
window.jQuery || document.write('<script src="../../assets/js/vendor/jquery.min.js"><\/script>')
</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</body>
</html>【讨论】：
这不是我所追求的。你正在复制引导程序的折叠/展开行为。我真正想要的只是在导航栏折叠时显示active 项目。
更新了答案【参考方案3】：
试试这个解决方案。虽然这需要进一步提高导航菜单链接的可点击性。
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">Project name</a>
</div>
<div id="navbar" class="collapse navbar-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="#about">About</a></li>
<li><a href="#contact">Contact</a></li>
</ul>
</div><!--/.nav-collapse -->
</div>
</nav>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="../../assets/js/vendor/jquery.min.js"><\/script>')</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
<script>
$ = window.jQuery
$(document).ready(function()
$('.navbar-brand').attr('data-brand',$('.navbar-brand').text())
var txtMenu = $('#navbar ul.navbar-nav .active').text();
$('.navbar-brand').text(txtMenu)
$('nav.navbar').on('hide.bs.collapse', function()
var txtM = $('#navbar ul.navbar-nav .active').text();
$('.navbar-brand').text(txtM)
)
$('nav.navbar').on('show.bs.collapse', function()
var txtB = $('.navbar-brand').attr('data-brand');
$('.navbar-brand').text(txtB)
)
)
</script>
</body></html>【讨论】：
谢谢，@seethrough。实际上我有点希望会有一个更漂亮的解决方案..这对我来说似乎真的很hacky（虽然我到目前为止还不是引导专家，所以也许这在引导中是正常的）。以上是关于Bootstrap 4：在导航栏折叠时显示活动导航项的主要内容，如果未能解决你的问题，请参考以下文章