Bootstrap NavBar Collapse 在点击时不起作用答案

【问题标题】：Bootstrap NavBar Collapse Isn't Working On ClickBootstrap NavBar Collapse 在点击时不起作用
【发布时间】：2020-04-03 05:03:29
【问题描述】：

导航栏折叠按钮有问题。

单击导航栏按钮时，我的导航栏折叠按钮不会打开。我假设数据切换不切换折叠有问题。

我也不确定 ul 标签中的 PHP 代码是否搞砸了。

感谢您的帮助。

<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
  <link rel="stylesheet" href="style.css">
  <link href="https://fonts.googleapis.com/css?family=Quicksand:300,500" rel="stylesheet">

  <link href="https://fonts.googleapis.com/css?family=Lora:400,700|Montserrat:300" rel="stylesheet">
  <script src="script.js"></script>
  <title>MyCar</title>

</head>
<body>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="index.php">MyCar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false">
  <span class="navbar-toggler-icon"></span>
</button>

<div class="navbar-collapse collapse" id="navbarSupportedContent">

  <ul class="navbar-nav mr-auto mt-2 mt-lg-0">
    <li class="nav-item">
      <a class="nav-link active" href="#">Home </a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="cars.php">Search Cars </a>
    </li>
    <li class="nav-item ">
      <a class="nav-link" href="sell.php">Sell Cars </a>
    </li>
    <li class="nav-item ">
      <a class="nav-link" href="financing.php">Financing </a>
    </li>
  </ul>
  <ul class="navbar-nav mt-2 mt-lg-0">
    <?php

        if(isset($_SESSION['username'])){

          echo '<li class="nav-item">
                  <a class="nav-link" href="profile.php">Welcome, '.$_SESSION['username'].'<span class="sr-only">(current)</span></a>
                </li>
                <li class="nav-item">
                  <a class="nav-link" href="?logout=true">Log Out</a>
                </li>'
                ;
        }
        else {
          echo '<li class="nav-item">
          <a class="nav-link" href="signup.php">Sign Up <span class="sr-only">(current)</span></a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="login.php">Log In</a>
        </li>';
        }



    ?>
    <!--<li class="nav-item">
      <a class="nav-link" href='?logout=true'>>Log Out</a>
    </li> -->
  </ul>
</div>
</nav>

【问题讨论】：

标签： html css twitter-bootstrap bootstrap-4

【解决方案1】：

您指向 Bootstrap.min.js 的链接不正确

更改<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js">
转入<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>

在下面工作sn-p：

<!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/4.4.1/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js"></script>
  <link href="https://fonts.googleapis.com/css?family=Lora:400,700|Montserrat:300" rel="stylesheet">
  <script src="script.js"></script>
  <title>MyCar</title>

</head>

<body>
  <nav class="navbar navbar-expand-lg navbar-light bg-light">
    <a class="navbar-brand" href="index.php">MyCar</a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false">
  <span class="navbar-toggler-icon"></span>
</button>

    <div class="navbar-collapse collapse" id="navbarSupportedContent">

      <ul class="navbar-nav mr-auto mt-2 mt-lg-0">
        <li class="nav-item">
          <a class="nav-link active" href="#">Home </a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="cars.php">Search Cars </a>
        </li>
        <li class="nav-item ">
          <a class="nav-link" href="sell.php">Sell Cars </a>
        </li>
        <li class="nav-item ">
          <a class="nav-link" href="financing.php">Financing </a>
        </li>
      </ul>
      <ul class="navbar-nav mt-2 mt-lg-0">
        <?php

        if(isset($_SESSION['username'])){

          echo '<li class="nav-item">
                  <a class="nav-link" href="profile.php">Welcome, '.$_SESSION['username'].'<span class="sr-only">(current)</span></a>
                </li>
                <li class="nav-item">
                  <a class="nav-link" href="?logout=true">Log Out</a>
                </li>'
                ;
        }
        else {
          echo '<li class="nav-item">
          <a class="nav-link" href="signup.php">Sign Up <span class="sr-only">(current)</span></a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="login.php">Log In</a>
        </li>';
        }



    ?>
          <!--<li class="nav-item">
      <a class="nav-link" href='?logout=true'>>Log Out</a>
    </li> -->
      </ul>
    </div>
  </nav>

</body>

</html>

【讨论】：