javascript - 如何在 Bootstrap 4 的下拉菜单上添加动画

标签 javascript css bootstrap-4

导航栏切换器折叠时有一个动画:

<!doctype html>
<html lang="en">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

    <title>Hello, world!</title>
  </head>
  <body>
    <nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <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="#">Link</a>
      </li>
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
          Dropdown
        </a>
        <div class="dropdown-menu" aria-labelledby="navbarDropdown">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>

    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>
  </body>
</html>

如何使用 Dropmenu 执行相同操作？

我一直在 Google 上搜索此内容，并在 Stackoverflow 上找到了一些答案，但这些脚本在这里不起作用。也许是因为他们使用了必需的库，但我没有找到任何相关信息。

最佳答案

您可以在 css 中使用以下代码在下拉菜单上添加过渡:

.dropdown .dropdown-menu {
  -webkit-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -moz-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -ms-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -o-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  max-height: 0;
  display: block;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
}

.dropdown.show .dropdown-menu {
  -webkit-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -moz-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -ms-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -o-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  max-height: 190px;
  opacity: 1;
  visibility: visible;
}

这是一个工作示例:

.dropdown .dropdown-menu {
  -webkit-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -moz-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -ms-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  -o-transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  transition: max-height 0.3s, opacity 0.2s 0.1s, visibility 0s 4s;
  max-height: 0;
  display: block;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
}

.dropdown.show .dropdown-menu {
  -webkit-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -moz-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -ms-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  -o-transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  transition: max-height 0.3s, opacity 0.2s, visibility 0s;
  max-height: 190px;
  opacity: 1;
  visibility: visible;
}
<!doctype html>
<html lang="en">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

  <title>Hello, world!</title>
</head>

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

    <div class="collapse navbar-collapse" id="navbarSupportedContent">
      <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="#">Link</a>
        </li>
        <li class="nav-item dropdown">
          <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
          Dropdown
        </a>
          <div class="dropdown-menu" aria-labelledby="navbarDropdown">
            <a class="dropdown-item" href="#">Action</a>
            <a class="dropdown-item" href="#">Another action</a>
            <div class="dropdown-divider"></div>
            <a class="dropdown-item" href="#">Something else here</a>
          </div>
        </li>
        <li class="nav-item">
          <a class="nav-link disabled" href="#">Disabled</a>
        </li>
      </ul>
      <form class="form-inline my-2 my-lg-0">
        <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
        <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
      </form>
    </div>
  </nav>

  <!-- Optional JavaScript -->
  <!-- jQuery first, then Popper.js, then Bootstrap JS -->
  <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
  <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>
</body>

</html>

Credits

关于javascript - 如何在 Bootstrap 4 的下拉菜单上添加动画，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52300887/

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