Bootstrap 4 可切换导航栏
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【中文标题】Bootstrap 4 可切换导航栏【英文标题】：Bootstrap 4 toggleable navbar 【发布时间】：2018-01-22 09:31:32 【问题描述】：我正在尝试从 Bootstrap 3.x 迁移到 4，但我遇到了新导航栏的问题。无论我选择 navbar-toggleable-x 的哪个选项，导航栏总是显示汉堡按钮，就像它被折叠一样。
这个 html 文档演示了我的问题。我在官方文档页面上得到了它。
<html>
<head>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js" integrity="sha384-h0AbiXch4ZDo7tp9hKZ4TsHbi047NrKGLO3SEJAg45jXxnGIfYzk4Si90RDIqNm1" crossorigin="anonymous"></script>
</head>
<body>
<nav class="navbar navbar-toggleable-md navbar-light bg-faded">
<button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<a class="navbar-brand" href="#">Navbar</a>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<ul class="navbar-nav">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Features</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Pricing</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
</ul>
</div>
</nav>
</body>
</html>
【问题讨论】：
将您的<nav> 弹出到 Bootply 并按预期运行：bootply.com/TWBmIowsXy ... 表明该问题与您的语法/bootstrap4 无关。
【参考方案1】：
自 Bootstrap 4 beta 起，toggleable 已替换为 expand。
现在它是“扩展”断点，而不是“切换”断点，因此逻辑会相应更改，因此 navbar-toggleable-md 现在将是 navbar-expand-lg..
https://www.codeply.com/go/Io0duaPkqz
<nav class="navbar navbar-expand-lg navbar-light bg-faded">
<button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<a class="navbar-brand" href="#">Navbar</a>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<ul class="navbar-nav">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Features</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Pricing</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
</ul>
</div>
</nav>
https://www.codeply.com/go/Io0duaPkqz
如果您希望导航栏水平展开，则需要 navbar-expand* 类，否则导航栏默认为移动的垂直折叠版本。
更多关于 Bootstrap 4 changes from alpha 6 to beta
【讨论】：
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