Bootstrap 4下拉菜单无法正常工作

Question

不确定是不是只有我遇到这个问题，我正在从Bootstrap 3迁移到v4，但下拉列表不起作用，甚至是从Bootstrap v4下拉列表中复制的最简单示例也无效。下面的代码显示了一个可点击的按钮，但没有任何下拉选项。我发现在刷新后的0.01秒内，当我点击按钮时，下拉菜单会出现。但之后就一直无法使用。以下是我的代码：

js

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js" integrity="sha384-3ceskX3iaEnIogmQchP8opvBy3Mi7Ce34nWjpBIwVTHfGYWQS9jwHDVRnpKKHJg7" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.3.7/js/tether.min.js" integrity="sha384-XTs3FgkjiBgo8qjEjBk0tGmf3wPrWtA6coPfQDfFEY8AnYJwjalXCiosYRBIBZX8" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.5/js/bootstrap.min.js" integrity="sha384-BLiI7JTZm+JWlgKa0M0kGRpJbF2J8q+qreVrKBC47e3K6BW78kGLrCkeRX6I9RoK" crossorigin="anonymous"></script>

CSS

<link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/css/tether-theme-arrows-dark.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.5/css/bootstrap.min.css" integrity="sha384-AysaV+vQoT3kOAXZkl02PThvDr8HYKPZhNT5h/CXfBThSRXQ6jW5DO2ekP5ViFdi" crossorigin="anonymous">

HTML

<div class="btn-group">
  <button type="button" class="btn btn-danger dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    Action
  </button>
  <div class="dropdown-menu">
    <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 class="dropdown-divider"></div>
    <a class="dropdown-item" href="#">Separated link</a>
  </div>
</div>

- warmjaijai

---

对我来说，问题在于我忘记添加Js链接。 - adam shamsudeen

Answer 1

在Bootstrap 4中，btn-group类不再用于下拉菜单。使用dropdown类作为父元素：

<div class="dropdown">
  <button type="button" class="btn btn-danger dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    Action
  </button>
  <div class="dropdown-menu">
    <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 class="dropdown-divider"></div>
    <a class="dropdown-item" href="#">Separated link</a>
  </div>
</div>

- Schrockwell

Answer 2

在Alpha 4.0.6中遇到了同样的问题。

我将bootstrap.css 3.3.7的.dropdown样式复制到dropdowns.less中，问题得到解决。

.dropup,
.dropdown {
  position: relative;
}

.dropdown-toggle::after {
  display: inline-block;
  width: 0;
  height: 0;
  margin-left: 0.3em;
  vertical-align: middle;
  content: "";
  border-top: 0.3em solid;
  border-right: 0.3em solid transparent;
  border-left: 0.3em solid transparent;
}

.dropdown-toggle:focus {
  outline: 0;
}

.dropup .dropdown-toggle::after {
  border-top: 0;
  border-bottom: 0.3em solid;
}

.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 0;
  z-index: 1000;
  display: none;
  float: left;
  min-width: 10rem;
  padding: 0.5rem 0;
  margin: 0.125rem 0 0;
  font-size: 1rem;
  color: #292b2c;
  text-align: left;
  list-style: none;
  background-color: #fff;
  -webkit-background-clip: padding-box;
          background-clip: padding-box;
  border: 1px solid rgba(0, 0, 0, 0.15);
  border-radius: 0.25rem;
}

.dropdown-divider {
  height: 1px;
  margin: 0.5rem 0;
  overflow: hidden;
  background-color: #eceeef;
}

.dropdown-item {
  display: block;
  width: 100%;
  padding: 3px 1.5rem;
  clear: both;
  font-weight: normal;
  color: #292b2c;
  text-align: inherit;
  white-space: nowrap;
  background: none;
  border: 0;
}

.dropdown-item:focus, .dropdown-item:hover {
  color: #1d1e1f;
  text-decoration: none;
  background-color: #f7f7f9;
}

.dropdown-item.active, .dropdown-item:active {
  color: #fff;
  text-decoration: none;
  background-color: #0275d8;
}

.dropdown-item.disabled, .dropdown-item:disabled {
  color: #636c72;
  cursor: not-allowed;
  background-color: transparent;
}

.show > .dropdown-menu {
  display: block;
}

.show > a {
  outline: 0;
}

.dropdown-menu-right {
  right: 0;
  left: auto;
}

.dropdown-menu-left {
  right: auto;
  left: 0;
}

.dropdown-header {
  display: block;
  padding: 0.5rem 1.5rem;
  margin-bottom: 0;
  font-size: 0.875rem;
  color: #636c72;
  white-space: nowrap;
}

.dropdown-backdrop {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 990;
}

.dropup .dropdown-menu {
  top: auto;
  bottom: 100%;
  margin-bottom: 0.125rem;
}

这不是一个有效的解决方案，但它可以工作 :-)

- Birger Püschl

---

下拉菜单是基于第三方库Popper.js构建的，它提供动态定位和视口检测功能。在引入Bootstrap的JavaScript之前，请确保包含popper.min.js。请查看文档。 - Zuul

根据@Zuul的说法，Popper必须在bootstrap.js之前加载。这就是我遇到的问题。 - Dave

Answer 3

将此代码添加到您的jQuery代码中。

$('.dropdown').click(function(){
  $('.dropdown-menu').toggleClass('show');
});

- Dushyanth Kandiah

---

是的，这个可以，但在版本4.4.1中需要添加"$(this).toggleClass('show');"... $('.dropdown').click(function(){ $('.dropdown-menu').toggleClass('show'); $(this).toggleClass('show'); }); - Sheo Sagar