Flex布局

启用Flex布局

使用display实用程序创建一个 flexbox 容器并将直接子元素转换为 flex 节点。可以使用额外的弹性属性进一步修改弹性容器和项目。

<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也有响应式变量。

• .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

使用方向实用程序设置弹性容器中弹性项目的方向。在大多数情况下，您可以省略此处的水平类，因为浏览器默认为row. 但是，您可能会遇到需要显式设置此值的情况（如响应式布局）。

用于.flex-row设置水平方向（浏览器默认），或.flex-row-reverse从相反的一侧开始水平方向。

<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>

用于.flex-column设置垂直方向，或.flex-column-reverse 从相反的一侧开始垂直方向。

<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>

响应式变量也存在于flex-direction.

• .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

justify-content

使用flexbox 容器上的justify-content实用程序来更改 flex 项目在主轴上的对齐方式（x 轴开始，y 轴 如果有 flex-direction: column）。从start（浏览器默认）或center、between、around、evenly、end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>

响应式变量也存在于justify-content.

• .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

对齐元素

使用flexbox 容器上的align-items实用程序来更改 flex 项目在横轴上的对齐方式（y 轴开始，x 轴，如果flex-direction: column）。从start（浏览器默认值）、end、center、baseline或stretch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>

响应式变量也存在于align-items.

• .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

对齐自我

在 flexbox 项目上使用align-self实用程序来单独更改它们在横轴上的对齐方式（开始时是 y 轴，如果是 x 轴flex-direction: column）。align-items从: start、end、center、baseline或stretch（浏览器默认值）相同的选项中进行选择。

<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>

响应式变量也存在于align-self.

• .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

充满

在一系列同级元素上使用.flex-fill类以强制它们的宽度等于它们的内容（或者如果它们的内容不超过它们的边框则宽度相等）同时占用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>

响应式变量也存在于flex-fill.

• .flex-fill
• .flex-sm-fill
• .flex-md-fill
• .flex-lg-fill
• .flex-xl-fill
• .flex-xxl-fill

增长和收缩

使用.flex-grow-*实用程序来切换弹性项目增长以填充可用空间的能力。在下面的示例中，.flex-grow-1元素使用了它可以使用的所有可用空间，同时为剩余的两个弹性项目留出了必要的空间。

<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>

如有必要，使用.flex-shrink-*实用程序来切换弹性项目的收缩能力。在下面的示例中，第二个带有.flex-shrink-1的弹性项目被迫将其内容换行，“收缩”以便为前一个带有.w-100的弹性项目留出更多空间。

<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也存在响应式变量。

• .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

当您将弹性对齐与自动边距混合使用时，Flexbox 可以做一些非常棒的事情。下面显示的是通过自动边距控制弹性项目的三个示例：默认（无自动边距）、向右排列两个项目 ( .me-auto) 和向左排列两个项目 ( .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>

使用对齐项

通过混合align-items, flex-direction: column和margin-top: auto或margin-bottom: auto垂直移动一个弹性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

更改弹性项目在弹性容器中的包装方式。从完全不换行（浏览器默认设置）.flex-nowrap、使用.flex-wrap换行或反向换行.flex-wrap-reverse中进行选择。

<div class="d-flex flex-nowrap">
  ...
</div>

<div class="d-flex flex-wrap">
  ...
</div>

<div class="d-flex flex-wrap-reverse">
  ...
</div>

响应式变量也存在于flex-wrap.

• .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

使用一些order实用程序更改特定弹性项目的视觉顺序，我们只提供将项目放在首位或末尾的选项，以及使用 DOM 顺序的重置。由于order采用 0 到 5 之间的任何整数值，为所需的任何其他值添加自定义 CSS。

<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>

响应式变量也存在于order.

• .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.order-first和.order-last类，它们分别通过应用order: -1和order: 6来更改order元素。

• .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实用程序将 flex 项目在横轴上对齐在一起。从start（浏览器默认）、center、between、around、stretch或end中选择。为了演示这些实用程序，我们强制执行flex-wrap: wrap并增加了弹性项目的数量。

小心！此属性对单行弹性项目没有影响。

<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>

响应式变量也存在于align-content.

• .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

想要从 Bootstrap 4复制媒体对象组件？使用一些 flex 实用程序可以立即重新创建它，这些实用程序允许比以前更加灵活和自定义。

<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>

并假设您想将图像旁边的内容垂直居中：

<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>

Sass

实用程序接口

Flexbox 实用程序在我们的实用程序 API 中声明scss/_utilities.scss。了解如何使用实用程序 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,
      ),
    ),