Bootstrap导航栏下拉故障

Question

因此，我只是从bootswatch复制了navbar表单的代码段，并直接导入了所需的JQuery，bootstrap css和js文件，如下面的代码段所示。 调整浏览器大小时，它正在响应，但是当我单击该按钮以获取导航栏的下拉菜单时，它会出现故障，不会下降并停留在那里，而是会自行切换。

代码中没有进行任何调整或更改，并且可以在bootswatch网站上正常运行，但不在此处。 谁能解释原因并给予解决？

 <link rel="stylesheet" href="https://bootswatch.com/4/united/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <nav class="navbar navbar-expand-lg navbar-dark bg-dark"> <a class="navbar-brand" href="#">Navbar</a> <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor02" aria-controls="navbarColor02" aria-expanded="false" aria-label="Toggle navigation" style=""> <span class="navbar-toggler-icon"></span> </button> <div class="collapse navbar-collapse" id="navbarColor02"> <ul class="navbar-nav mr-auto"> <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"> <a class="nav-link" href="#">About</a> </li> </ul> <form class="form-inline my-2 my-lg-0"> <input class="form-control mr-sm-2" placeholder="Search" type="text"> <button class="btn btn-secondary my-2 my-sm-0" type="submit">Search</button> </form> </div> </nav> 

Answer 1

问题在于您所说的事情已经改变了。 Bootstrap和jQuery文件。 您正在使用Bootstrap 3.3.7中的jQuery和Bootstrap 4中的CSS，它们之间存在冲突。 另请注意，Bootstrap 4还需要Popper.js 。

更改两个Bootstrap文件以使用Bootstrap 4（包括Popper）可解决此问题：

 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.6/umd/popper.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js"></script> <nav class="navbar navbar-expand-lg navbar-dark bg-dark"> <a class="navbar-brand" href="#">Navbar</a> <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor02" aria-controls="navbarColor02" aria-expanded="false" aria-label="Toggle navigation" style=""> <span class="navbar-toggler-icon"></span> </button> <div class="collapse navbar-collapse" id="navbarColor02"> <ul class="navbar-nav mr-auto"> <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"> <a class="nav-link" href="#">About</a> </li> </ul> <form class="form-inline my-2 my-lg-0"> <input class="form-control mr-sm-2" placeholder="Search" type="text"> <button class="btn btn-secondary my-2 my-sm-0" type="submit">Search</button> </form> </div> </nav> 

希望这可以帮助！ :)

Answer 2

这是因为bootswatch使用的是bootstrap 4.0 beta而不是3对于bootstrap4您将需要popper.js

请参阅下面的演示

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.13.0/umd/popper.js"></script> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css"> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js"></script> <nav class="navbar navbar-expand-lg navbar-dark bg-primary"> <a class="navbar-brand" href="#">Navbar</a> <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor01" aria-controls="navbarColor01" aria-expanded="false" aria-label="Toggle navigation" style=""> <span class="navbar-toggler-icon"></span> </button> <div class="collapse navbar-collapse" id="navbarColor01"> <ul class="navbar-nav mr-auto"> <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"> <a class="nav-link" href="#">About</a> </li> </ul> <form class="form-inline my-2 my-lg-0"> <input class="form-control mr-sm-2" type="text" placeholder="Search"> <button class="btn btn-secondary my-2 my-sm-0" type="submit">Search</button> </form> </div> </nav> 

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编辑

在尝试包含popper.js请记住仅使用umd特定目录，而不使用esm或其他任何目录。 有关详细信息，请参见上一期