后浪云Bootstrap4教程：Bootstrap4 下拉菜单
Bootstrap4 下拉菜单
Bootstrap4 下拉菜单依赖于 popper.min.js。
下拉菜单是可切换的，是以列表格式显示链接的上下文菜单。
实例
<
div
class
=
"
dropdown
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary dropdown-toggle
"
data-toggle
=
"
dropdown
"
>
Dropdown button
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Link 1
</
a
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Link 2
</
a
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Link 3
</
a
>
</
div
>
</
div
>
尝试一下 »
实例解析
.dropdown 类用来指定一个下拉菜单。
我们可以使用一个按钮或链接来打开下拉菜单， 按钮或链接需要添加 .dropdown-toggle 和 data-toggle="dropdown" 属性。
<div> 元素上添加 .dropdown-menu 类来设置实现下拉菜单，然后在下拉菜单的选项中添加 .dropdown-item 类。
我们也可以在 <a> 标签中使用：
实例
<
div
class
=
"
dropdown
"
>
<
a
class
=
"
btn btn-secondary dropdown-toggle
"
href
=
"
#
"
role
=
"
button
"
id
=
"
dropdownMenuLink
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
Dropdown link
</
a
>
<
div
class
=
"
dropdown-menu
"
aria-labelledby
=
"
dropdownMenuLink
"
>
<
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
>
</
div
>
尝试一下 »
下拉菜单中的分割线
.dropdown-divider 类用于在下拉菜单中创建一个水平的分割线：
实例
<
div
class
=
"
dropdown-divider
"
>
</
div
>
尝试一下 »
下拉菜单中的标题
.dropdown-header 类用于在下拉菜单中添加标题：
实例
<
div
class
=
"
dropdown-header
"
>
Dropdown header 1
</
div
>
尝试一下 »
下拉菜单中的可用项与禁用项
.active 类会让下拉菜单的选项高亮显示 (添加蓝色背景)。
如果要禁用下拉菜单的选项，可以使用.disabled 类。
实例
<
a
class
=
"
dropdown-item active
"
href
=
"
#
"
>
Active
</
a
>
<
a
class
=
"
dropdown-item disabled
"
href
=
"
#
"
>
Disabled
</
a
>
尝试一下 »
下拉菜单的定位
如果我们想让下拉菜单右对齐，可以在元素上的 .dropdown-menu 类后添加 .dropdown-menu-right 类。
实例
<
div
class
=
"
dropdown-menu dropdown-menu-right
"
>
尝试一下 »
下拉菜单弹出方向设置
下拉菜单弹出方向默认为向下，当然我们也可以设置不同的方向。
指定向右弹出的下拉菜单
如果你希望下拉菜单向右弹出，可以在 div 元素上添加 "dropright" 类:
实例
<!--
Default dropright button
-->
<
div
class
=
"
btn-group dropright
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
Dropright
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
<!--
Split dropright button
-->
<
div
class
=
"
btn-group dropright
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary
"
>
Split dropright
</
button
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle dropdown-toggle-split
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
<
span
class
=
"
sr-only
"
>
Toggle Dropright
</
span
>
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
尝试一下 »
指定向上弹出的上拉菜单
如果你希望上拉菜单向上弹出，可以在 div 元素上添加 "dropup" 类:
实例
<!--
Default dropup button
-->
<
div
class
=
"
btn-group dropup
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
Dropup
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
<!--
Split dropup button
-->
<
div
class
=
"
btn-group dropup
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary
"
>
Split dropup
</
button
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle dropdown-toggle-split
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
<
span
class
=
"
sr-only
"
>
Toggle Dropdown
</
span
>
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
尝试一下 »
指定向左边弹出的下拉菜单
如果你希望下拉菜单向上弹出，可以在 div 元素上添加 "dropleft" 类:
实例
<!--
Default dropleft button
-->
<
div
class
=
"
btn-group dropleft
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
Dropleft
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
<!--
Split dropleft button
-->
<
div
class
=
"
btn-group
"
>
<
div
class
=
"
btn-group dropleft
"
role
=
"
group
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary dropdown-toggle dropdown-toggle-split
"
data-toggle
=
"
dropdown
"
aria-haspopup
=
"
true
"
aria-expanded
=
"
false
"
>
<
span
class
=
"
sr-only
"
>
Toggle Dropleft
</
span
>
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<!--
Dropdown menu links
-->
</
div
>
</
div
>
<
button
type
=
"
button
"
class
=
"
btn btn-secondary
"
>
Split dropleft
</
button
>
</
div
>
尝试一下 »
下拉菜单设置文本
.dropdown-item-text 类可以设置下拉菜单中的文本项：
实例
<
div
class
=
"
dropdown-menu
"
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
链接 1
</
a
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
链接 2
</
a
>
<
a
class
=
"
dropdown-item-text
"
href
=
"
#
"
>
文本链接
</
a
>
<
span
class
=
"
dropdown-item-text
"
>
仅仅是文本
</
span
>
</
div
>
尝试一下 »
按钮中设置下拉菜单
我们可以在按钮中添加下拉菜单：
实例
<
div
class
=
"
btn-group
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary
"
>
Sony
</
button
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary dropdown-toggle dropdown-toggle-split
"
data-toggle
=
"
dropdown
"
>
<
span
class
=
"
caret
"
>
</
span
>
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Tablet
</
a
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Smartphone
</
a
>
</
div
>
</
div
>
尝试一下 »
垂直按钮组带下拉菜单：
实例
<
div
class
=
"
btn-group-vertical
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary
"
>
Apple
</
button
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary
"
>
Samsung
</
button
>
<
div
class
=
"
btn-group
"
>
<
button
type
=
"
button
"
class
=
"
btn btn-primary dropdown-toggle
"
data-toggle
=
"
dropdown
"
>
Sony
</
button
>
<
div
class
=
"
dropdown-menu
"
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Tablet
</
a
>
<
a
class
=
"
dropdown-item
"
href
=
"
#
"
>
Smartphone
</
a
>
</
div
>
</
div
>
</
div
>
尝试一下 »