Bootstrap 下拉菜单.dropdown的具体使用方法

本章将具体讲解下拉菜单的交互。使用下拉菜单（Dropdown）插件，您可以向任何组件（比如导航栏、标签页、胶囊式导航菜单、按钮等）添加下拉菜单。

下拉菜单.dropdown具体用法

.dropdown <下拉菜单触发器button+下拉菜单ul

.dropdown　包裹层

.dropdown-toggle 下拉菜单触发器

data-toggle=”dropdown 自定义属性可以与js关联起来

.dropdown-menu 下拉菜单

具体实例：

<div class="dropdown" 
 <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown" aria-haspopup="true" aria-expanded="true" 
  Dropdown
  <span class="caret" </span 
 </button 
 <ul class="dropdown-menu" aria-labelledby="dropdownMenu1" 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Another action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Something else here</a </li 
  <li role="separator" class="divider" </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Separated link</a </li 
 </ul 
</div

如果你想让菜单默认是打开状态，需要添加一个.open的类

<div class="dropdown open" 
 <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown" aria-haspopup="true" aria-expanded="true" 
  Dropdown
  <span class="caret" </span 
 </button 
 <ul class="dropdown-menu" aria-labelledby="dropdownMenu1" 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Another action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Something else here</a </li 
  <li role="separator" class="divider" </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Separated link</a </li 
 </ul 
</div

.dropup 向上弹出菜单

通过为下拉菜单的父元素设置 .dropup 类，可以让菜单向上弹出（默认是向下弹出的）

<div class="dropup" 
 <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu2" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" 
  Dropup
  <span class="caret" </span 
 </button 
 <ul class="dropdown-menu" aria-labelledby="dropdownMenu2" 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Another action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Something else here</a </li 
  <li role="separator" class="divider" </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Separated link</a </li 
 </ul 
</div

1、对齐方式：默认左对齐

右对齐：给.dropdown-menu添加.dropdown-menu-right类就可以

注意：它是以父级的位置来对齐的

怎么样让下拉菜单以下拉菜单触发器的右端对齐呢？那就需要给下拉菜单触发器button添加一个.btn block的类

<div class="dropup" 
 <button class="btn btn-default dropdown-toggle btn-block" type="button" id="dropdownMenu2" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" 
  Dropup
  <span class="caret" </span 
 </button 
 <ul class="dropdown-menu dropdown-menu-right " aria-labelledby="dropdownMenu2" 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Another action</a </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Something else here</a </li 
  <li role="separator" class="divider" </li 
  <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Separated link</a </li 
 </ul 
</div

2、下拉菜单的标题 dropdown-header

在任何下拉菜单中均可通过添加标题来标明一组动作。

如果想让下拉菜单的标题居中，就需要添加一个.text-center的类

<ul class="dropdown-menu" aria-labelledby="dropdownMenu3" 
 ...
 <li class="dropdown-header text-center" Dropdown header</li 
 ...
</ul

3、分割线： .divider　

为下拉菜单添加一条分割线，用于将多个链接分组。

<ul class="dropdown-menu" aria-labelledby="dropdownMenuDivider" 
 ...
 <li role="separator" class="divider" </li 
 ...
</ul

4、禁用菜单：disabled

为下拉菜单中的 <li 元素添加 .disabled 类，从而禁用相应的菜单项。

<ul class="dropdown-menu" aria-labelledby="dropdownMenu4" 
 <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Regular link</a </li 
 <li class="disabled" <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Disabled link</a </li 
 <li <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow"  Another link</a </li 
</ul

注意：

aria-haspopup=”true” 　aria-expanded=”true” 为需要借助屏幕阅读器的特殊人群设置的

id=”dropdownMenu1″　aria-labelledby=”dropdownMenu1″ 通过id将触发器和下拉菜单关联起来

以上就是本文的全部内容，希望对大家的学习有所帮助。