Flex
使用一整套响应式 flexbox 实用程序,快速管理网格列、导航、组件等的布局、对齐和大小。对于更复杂的实现,可能需要自定义 CSS。
启用 flex 行为
应用 display
实用程序以创建 flexbox 容器,并将直接子元素转换为 flex 项目。可以使用其他 flex 属性进一步修改 flex 容器和项目。
<div class="d-flex p-2">I'm a flexbox container!</div>
<div class="d-inline-flex p-2">I'm an inline flexbox container!</div>
.d-flex
和 .d-inline-flex
也有响应式变体。
.d-flex
.d-inline-flex
.d-sm-flex
.d-sm-inline-flex
.d-md-flex
.d-md-inline-flex
.d-lg-flex
.d-lg-inline-flex
.d-xl-flex
.d-xl-inline-flex
.d-xxl-flex
.d-xxl-inline-flex
方向
使用方向实用程序在 flex 容器中设置 flex 项目的方向。在大多数情况下,你可以省略此处的水平类,因为浏览器的默认值为 row
。但是,你可能会遇到需要显式设置此值的情况(例如响应式布局)。
使用 .flex-row
设置水平方向(浏览器的默认值),或使用 .flex-row-reverse
从另一侧开始水平方向。
<div class="d-flex flex-row mb-3">
<div class="p-2">Flex item 1</div>
<div class="p-2">Flex item 2</div>
<div class="p-2">Flex item 3</div>
</div>
<div class="d-flex flex-row-reverse">
<div class="p-2">Flex item 1</div>
<div class="p-2">Flex item 2</div>
<div class="p-2">Flex item 3</div>
</div>
使用 .flex-column
设置垂直方向,或使用 .flex-column-reverse
从另一侧开始垂直方向。
<div class="d-flex flex-column mb-3">
<div class="p-2">Flex item 1</div>
<div class="p-2">Flex item 2</div>
<div class="p-2">Flex item 3</div>
</div>
<div class="d-flex flex-column-reverse">
<div class="p-2">Flex item 1</div>
<div class="p-2">Flex item 2</div>
<div class="p-2">Flex item 3</div>
</div>
flex-direction
也有响应式变体。
.flex-row
.flex-row-reverse
.flex-column
.flex-column-reverse
.flex-sm-row
.flex-sm-row-reverse
.flex-sm-column
.flex-sm-column-reverse
.flex-md-row
.flex-md-row-reverse
.flex-md-column
.flex-md-column-reverse
.flex-lg-row
.flex-lg-row-reverse
.flex-lg-column
.flex-lg-column-reverse
.flex-xl-row
.flex-xl-row-reverse
.flex-xl-column
.flex-xl-column-reverse
.flex-xxl-row
.flex-xxl-row-reverse
.flex-xxl-column
.flex-xxl-column-reverse
内容对齐
在 flexbox 容器中使用 justify-content
实用程序来更改弹性项目在主轴(开始时的 x 轴,如果 flex-direction: column
,则为 y 轴)上的对齐方式。从 start
(浏览器默认值)、end
、center
、between
、around
或 evenly
中选择。
<div class="d-flex justify-content-start">...</div>
<div class="d-flex justify-content-end">...</div>
<div class="d-flex justify-content-center">...</div>
<div class="d-flex justify-content-between">...</div>
<div class="d-flex justify-content-around">...</div>
<div class="d-flex justify-content-evenly">...</div>
justify-content
也有响应式变化。
.justify-content-start
.justify-content-end
.justify-content-center
.justify-content-between
.justify-content-around
.justify-content-evenly
.justify-content-sm-start
.justify-content-sm-end
.justify-content-sm-center
.justify-content-sm-between
.justify-content-sm-around
.justify-content-sm-evenly
.justify-content-md-start
.justify-content-md-end
.justify-content-md-center
.justify-content-md-between
.justify-content-md-around
.justify-content-md-evenly
.justify-content-lg-start
.justify-content-lg-end
.justify-content-lg-center
.justify-content-lg-between
.justify-content-lg-around
.justify-content-lg-evenly
.justify-content-xl-start
.justify-content-xl-end
.justify-content-xl-center
.justify-content-xl-between
.justify-content-xl-around
.justify-content-xl-evenly
.justify-content-xxl-start
.justify-content-xxl-end
.justify-content-xxl-center
.justify-content-xxl-between
.justify-content-xxl-around
.justify-content-xxl-evenly
项目对齐
在 flexbox 容器中使用 align-items
实用程序来更改弹性项目在交叉轴(开始时的 y 轴,如果 flex-direction: column
,则为 x 轴)上的对齐方式。从 start
、end
、center
、baseline
或 stretch
(浏览器默认值)中选择。
<div class="d-flex align-items-start">...</div>
<div class="d-flex align-items-end">...</div>
<div class="d-flex align-items-center">...</div>
<div class="d-flex align-items-baseline">...</div>
<div class="d-flex align-items-stretch">...</div>
align-items
也有响应式变化。
.align-items-start
.align-items-end
.align-items-center
.align-items-baseline
.align-items-stretch
.align-items-sm-start
.align-items-sm-end
.align-items-sm-center
.align-items-sm-baseline
.align-items-sm-stretch
.align-items-md-start
.align-items-md-end
.align-items-md-center
.align-items-md-baseline
.align-items-md-stretch
.align-items-lg-start
.align-items-lg-end
.align-items-lg-center
.align-items-lg-baseline
.align-items-lg-stretch
.align-items-xl-start
.align-items-xl-end
.align-items-xl-center
.align-items-xl-baseline
.align-items-xl-stretch
.align-items-xxl-start
.align-items-xxl-end
.align-items-xxl-center
.align-items-xxl-baseline
.align-items-xxl-stretch
对齐自身
在 flexbox 项目上使用 align-self
实用程序,以单独更改它们在交叉轴(开始时的 y 轴,如果 flex-direction: column
则为 x 轴)上的对齐方式。从与 align-items
相同的选项中选择:start
、end
、center
、baseline
或 stretch
(浏览器默认设置)。
<div class="align-self-start">Aligned flex item</div>
<div class="align-self-end">Aligned flex item</div>
<div class="align-self-center">Aligned flex item</div>
<div class="align-self-baseline">Aligned flex item</div>
<div class="align-self-stretch">Aligned flex item</div>
align-self
也有响应式变体。
.align-self-start
.align-self-end
.align-self-center
.align-self-baseline
.align-self-stretch
.align-self-sm-start
.align-self-sm-end
.align-self-sm-center
.align-self-sm-baseline
.align-self-sm-stretch
.align-self-md-start
.align-self-md-end
.align-self-md-center
.align-self-md-baseline
.align-self-md-stretch
.align-self-lg-start
.align-self-lg-end
.align-self-lg-center
.align-self-lg-baseline
.align-self-lg-stretch
.align-self-xl-start
.align-self-xl-end
.align-self-xl-center
.align-self-xl-baseline
.align-self-xl-stretch
.align-self-xxl-start
.align-self-xxl-end
.align-self-xxl-center
.align-self-xxl-baseline
.align-self-xxl-stretch
填充
对一系列同级元素使用 .flex-fill
类,以强制它们的宽度等于其内容(如果其内容没有超出其边框框,则为相等宽度),同时占据所有可用的水平空间。
<div class="d-flex">
<div class="p-2 flex-fill">Flex item with a lot of content</div>
<div class="p-2 flex-fill">Flex item</div>
<div class="p-2 flex-fill">Flex item</div>
</div>
flex-fill
也有响应式变体。
.flex-fill
.flex-sm-fill
.flex-md-fill
.flex-lg-fill
.flex-xl-fill
.flex-xxl-fill
增长和缩小
使用 .flex-grow-*
实用程序切换 flex 项目填充可用空间的增长能力。在下面的示例中,.flex-grow-1
元素使用其可以使用的所有可用空间,同时为剩余的两个 flex 项目留出必要的空间。
<div class="d-flex">
<div class="p-2 flex-grow-1">Flex item</div>
<div class="p-2">Flex item</div>
<div class="p-2">Third flex item</div>
</div>
使用 .flex-shrink-*
实用程序切换 flex 项目在必要时缩小的能力。在下面的示例中,带有 .flex-shrink-1
的第二个 flex 项目被迫将其内容换行,以“收缩”为带有 .w-100
的前一个 flex 项目留出更多空间。
<div class="d-flex">
<div class="p-2 w-100">Flex item</div>
<div class="p-2 flex-shrink-1">Flex item</div>
</div>
flex-grow
和 flex-shrink
也有响应式变体。
.flex-{grow|shrink}-0
.flex-{grow|shrink}-1
.flex-sm-{grow|shrink}-0
.flex-sm-{grow|shrink}-1
.flex-md-{grow|shrink}-0
.flex-md-{grow|shrink}-1
.flex-lg-{grow|shrink}-0
.flex-lg-{grow|shrink}-1
.flex-xl-{grow|shrink}-0
.flex-xl-{grow|shrink}-1
.flex-xxl-{grow|shrink}-0
.flex-xxl-{grow|shrink}-1
自动边距
当将 flex 对齐与自动边距混合时,Flexbox 可以做一些非常棒的事情。下面显示了通过自动边距控制 flex 项目的三个示例:默认(无自动边距)、将两个项目推向右侧(.me-auto
)以及将两个项目推向左侧(.ms-auto
)。
<div class="d-flex mb-3">
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
</div>
<div class="d-flex mb-3">
<div class="me-auto p-2">Flex item</div>
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
</div>
<div class="d-flex mb-3">
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
<div class="ms-auto p-2">Flex item</div>
</div>
与 align-items 一起使用
通过混合 align-items
、flex-direction: column
以及 margin-top: auto
或 margin-bottom: auto
,垂直移动一个 flex 项目到容器的顶部或底部。
<div class="d-flex align-items-start flex-column mb-3" style="height: 200px;">
<div class="mb-auto p-2">Flex item</div>
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
</div>
<div class="d-flex align-items-end flex-column mb-3" style="height: 200px;">
<div class="p-2">Flex item</div>
<div class="p-2">Flex item</div>
<div class="mt-auto p-2">Flex item</div>
</div>
换行
更改 flex 项目在 flex 容器中换行的方式。使用 .flex-nowrap
选择根本不换行(浏览器默认值),使用 .flex-wrap
换行,或使用 .flex-wrap-reverse
反向换行。
<div class="d-flex flex-nowrap">
...
</div>
<div class="d-flex flex-wrap">
...
</div>
<div class="d-flex flex-wrap-reverse">
...
</div>
flex-wrap
也有响应式变体。
.flex-nowrap
.flex-wrap
.flex-wrap-reverse
.flex-sm-nowrap
.flex-sm-wrap
.flex-sm-wrap-reverse
.flex-md-nowrap
.flex-md-wrap
.flex-md-wrap-reverse
.flex-lg-nowrap
.flex-lg-wrap
.flex-lg-wrap-reverse
.flex-xl-nowrap
.flex-xl-wrap
.flex-xl-wrap-reverse
.flex-xxl-nowrap
.flex-xxl-wrap
.flex-xxl-wrap-reverse
顺序
使用少数 order
实用程序更改特定 flex 项目的视觉顺序。我们仅提供将项目设为第一个或最后一个的选项,以及使用 DOM 顺序的重置。由于 order
接受 0 到 5 的任何整数值,因此可添加自定义 CSS 以获取所需的任何其他值。
<div class="d-flex flex-nowrap">
<div class="order-3 p-2">First flex item</div>
<div class="order-2 p-2">Second flex item</div>
<div class="order-1 p-2">Third flex item</div>
</div>
order
也有响应式变体。
.order-0
.order-1
.order-2
.order-3
.order-4
.order-5
.order-sm-0
.order-sm-1
.order-sm-2
.order-sm-3
.order-sm-4
.order-sm-5
.order-md-0
.order-md-1
.order-md-2
.order-md-3
.order-md-4
.order-md-5
.order-lg-0
.order-lg-1
.order-lg-2
.order-lg-3
.order-lg-4
.order-lg-5
.order-xl-0
.order-xl-1
.order-xl-2
.order-xl-3
.order-xl-4
.order-xl-5
.order-xxl-0
.order-xxl-1
.order-xxl-2
.order-xxl-3
.order-xxl-4
.order-xxl-5
此外,还有响应式的 .order-first
和 .order-last
类,它们分别通过应用 order: -1
和 order: 6
来更改元素的 order
。
.order-first
.order-last
.order-sm-first
.order-sm-last
.order-md-first
.order-md-last
.order-lg-first
.order-lg-last
.order-xl-first
.order-xl-last
.order-xxl-first
.order-xxl-last
对齐内容
在 flexbox 容器上使用 align-content
实用程序,以在交叉轴上一起对齐 flex 项目。从 start
(浏览器默认值)、end
、center
、between
、around
或 stretch
中进行选择。为了演示这些实用程序,我们强制执行了 flex-wrap: wrap
并增加了 flex 项目的数量。
注意!此属性对单行 flex 项目无效。
<div class="d-flex align-content-start flex-wrap">
...
</div>
<div class="d-flex align-content-end flex-wrap">...</div>
<div class="d-flex align-content-center flex-wrap">...</div>
<div class="d-flex align-content-between flex-wrap">...</div>
<div class="d-flex align-content-around flex-wrap">...</div>
<div class="d-flex align-content-stretch flex-wrap">...</div>
align-content
还存在响应式变体。
.align-content-start
.align-content-end
.align-content-center
.align-content-between
.align-content-around
.align-content-stretch
.align-content-sm-start
.align-content-sm-end
.align-content-sm-center
.align-content-sm-between
.align-content-sm-around
.align-content-sm-stretch
.align-content-md-start
.align-content-md-end
.align-content-md-center
.align-content-md-between
.align-content-md-around
.align-content-md-stretch
.align-content-lg-start
.align-content-lg-end
.align-content-lg-center
.align-content-lg-between
.align-content-lg-around
.align-content-lg-stretch
.align-content-xl-start
.align-content-xl-end
.align-content-xl-center
.align-content-xl-between
.align-content-xl-around
.align-content-xl-stretch
.align-content-xxl-start
.align-content-xxl-end
.align-content-xxl-center
.align-content-xxl-between
.align-content-xxl-around
.align-content-xxl-stretch
媒体对象
想要复制 Bootstrap 4 中的 媒体对象组件?使用一些 flex 实用工具即可在短时间内重新创建它,这些实用工具比以前提供了更大的灵活性和自定义功能。
<div class="d-flex">
<div class="flex-shrink-0">
<img src="..." alt="...">
</div>
<div class="flex-grow-1 ms-3">
This is some content from a media component. You can replace this with any content and adjust it as needed.
</div>
</div>
假设你想将内容垂直居中放置在图像旁边
<div class="d-flex align-items-center">
<div class="flex-shrink-0">
<img src="..." alt="...">
</div>
<div class="flex-grow-1 ms-3">
This is some content from a media component. You can replace this with any content and adjust it as needed.
</div>
</div>
CSS
Sass 实用工具 API
Flexbox 实用工具在 scss/_utilities.scss
中的实用工具 API 中声明。了解如何使用实用工具 API。
"flex": (
responsive: true,
property: flex,
values: (fill: 1 1 auto)
),
"flex-direction": (
responsive: true,
property: flex-direction,
class: flex,
values: row column row-reverse column-reverse
),
"flex-grow": (
responsive: true,
property: flex-grow,
class: flex,
values: (
grow-0: 0,
grow-1: 1,
)
),
"flex-shrink": (
responsive: true,
property: flex-shrink,
class: flex,
values: (
shrink-0: 0,
shrink-1: 1,
)
),
"flex-wrap": (
responsive: true,
property: flex-wrap,
class: flex,
values: wrap nowrap wrap-reverse
),
"justify-content": (
responsive: true,
property: justify-content,
values: (
start: flex-start,
end: flex-end,
center: center,
between: space-between,
around: space-around,
evenly: space-evenly,
)
),
"align-items": (
responsive: true,
property: align-items,
values: (
start: flex-start,
end: flex-end,
center: center,
baseline: baseline,
stretch: stretch,
)
),
"align-content": (
responsive: true,
property: align-content,
values: (
start: flex-start,
end: flex-end,
center: center,
between: space-between,
around: space-around,
stretch: stretch,
)
),
"align-self": (
responsive: true,
property: align-self,
values: (
auto: auto,
start: flex-start,
end: flex-end,
center: center,
baseline: baseline,
stretch: stretch,
)
),
"order": (
responsive: true,
property: order,
values: (
first: -1,
0: 0,
1: 1,
2: 2,
3: 3,
4: 4,
5: 5,
last: 6,
),
),