导航栏按钮就是不出现，我不知道哪里出了问题，我确定代码是正确的，我甚至有jquery文件。
这就是代码。
<!doctype html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<link rel="stylesheet" href="style.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
</head>
<body>
<header>
<nav class="navbar navbar-expand-md navbar-light bg-light sticky-top">
<div class="container-fluid">
<a class="navbar-brand" href="#"><img src="img/logo.png"></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive">
<span class="navbar-toggler-icon"></span>
</button>
</div>
</nav>
</header>
</body>
</html>
你用了 navbar-expand-md 类，因为只有在分辨率小于768px的情况下，你的toggle才会可见，对于更高的分辨率，你可以使用 navbar-expand-lg 或 navbar-expand-xl 类。如果你想让它在所有屏幕上都能看到，只需删除类的 navbar-expand
<body>
<header>
<nav class="navbar navbar-light bg-light sticky-top">
<div class="container-fluid">
<a class="navbar-brand" href="#"><img src="img/logo.png"></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive">
<span class="navbar-toggler-icon"></span>
</button>
</div>
</nav>
</header>
你的代码没有任何意义。你可以自己调整一下试试吗？导航条切换器也需要有一个特定的宽度值才能显示。
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">***Your İmg Here***</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNav">
<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>
</ul>
</div>
</nav>