彈性盒子（Flex）

啟用flex

使用display通用類別來創建一個flexbox容器，并將直屬的子元素轉換為flex屬性。增加額外的flex屬性，也能夠進一步修改flex容器和屬性。

<div class="d-flex p-2 bd-highlight">I'm a flexbox container!</div>

<div class="d-inline-flex p-2 bd-highlight">I'm an inline flexbox container!</div>

.d-flex和.d-inline-flex也包含響應式的變化。

• .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

透過通用類別來設定flex容器與內層flex的方向，在大多的情況下你可以忽略水平的class，因為瀏覽器預設值是row。不過有些特定情境下需要特別設定這個值（像是響應式情境）。

使用.flex-row來設定水平的方向（瀏覽器預設值），或是使用.flex-row-reverse來作水平方向的反轉。

<div class="d-flex flex-row bd-highlight mb-3">
<div class="p-2 bd-highlight">Flex item 1</div>
<div class="p-2 bd-highlight">Flex item 2</div>
<div class="p-2 bd-highlight">Flex item 3</div>
</div>
<div class="d-flex flex-row-reverse bd-highlight">
<div class="p-2 bd-highlight">Flex item 1</div>
<div class="p-2 bd-highlight">Flex item 2</div>
<div class="p-2 bd-highlight">Flex item 3</div>
</div>

使用.flex-column設置垂直方向，或者使用.flex-column-reverse作垂直方向的反轉。

<div class="d-flex flex-column bd-highlight mb-3">
<div class="p-2 bd-highlight">Flex item 1</div>
<div class="p-2 bd-highlight">Flex item 2</div>
<div class="p-2 bd-highlight">Flex item 3</div>
</div>
<div class="d-flex flex-column-reverse bd-highlight">
<div class="p-2 bd-highlight">Flex item 1</div>
<div class="p-2 bd-highlight">Flex item 2</div>
<div class="p-2 bd-highlight">Flex item 3</div>
</div>

flex-direction的響應式變化。

• .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

調整內容

使用flexbox容器上的justify-content通用類別改變flex物件在主軸上的對齊（x軸開始，如果flex-direction: column則為y軸）。從start（瀏覽器預設），end、center、between、around或evenly中做選擇。

<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的響應式變化。

• .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

對齊項目

在flexbox容器上使用align-items工具改變橫軸上flex物件的對齊（y軸開始，如果設定flex-direction: column則為x軸），從start、end、center、baseline或是stretch（瀏覽器預設）中做選擇。

<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包含的響應式變化。

• .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

自身對齊

使用flexbox物件上的align-self通用類別單獨改變在橫軸上的對齊（y軸開始，如果設定flex-direction: column，則為x軸）。從與align-items相同的選項中選擇：start、end、center、baseline、或是stretch（溜覽器預設）。

<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的響應式變化。

• .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

在一系列的同級元素上使用.flex-fill來強制設定它們的寬度與內容相等（如果它們的內容不超過邊框，則各個寬度相等），同時占用所有可用的水平空間。

<div class="d-flex bd-highlight">
<div class="p-2 flex-fill bd-highlight">Flex item with a lot of content</div>
<div class="p-2 flex-fill bd-highlight">Flex item</div>
<div class="p-2 flex-fill bd-highlight">Flex item</div>
</div>

flex-fill同樣包含響應式的變化。

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

伸縮值

使用.flex-grow-*通用類別來切換flex項目彈性增長、填充可用空間的能力。在下面的示例中，.flex-grow-1元素使用它可以使用的所有可用空間，同時允許剩馀的兩個flex物件保留必要的空間。

<div class="d-flex bd-highlight">
<div class="p-2 flex-grow-1 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Third flex item</div>
</div>

如果需要，使用.flex-shrink-*通用類別來切換項目的縮小能力。在下面的示例中，帶有.flex-shrink-1的第二個flex項目的文字內容會被強制換行，”收縮”以允許更多空間用于上一個帶有.w-100的flex項目。

<div class="d-flex bd-highlight">
<div class="p-2 w-100 bd-highlight">Flex item</div>
<div class="p-2 flex-shrink-1 bd-highlight">Flex item</div>
</div>

flex-grow和flex-shrink也包含響應式的變化。

• .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

自動邊距

當你混用Flex對齊與auto margin時候，Flexbox可以執行一些令人驚艷的功能。下面的示例是透過自動margin來控制flex項目的三個案例：預設（無自動margin），向右推兩個項目（.me-auto），并向左推兩個項目（.ms-auto）。

<div class="d-flex bd-highlight mb-3">
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex bd-highlight mb-3">
<div class="me-auto p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex bd-highlight mb-3">
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="ms-auto p-2 bd-highlight">Flex item</div>
</div>

搭配 align-items

混合以下屬性align-items、flex-direction: column，和margin-top: auto或margin-bottom: auto，會將一個flex項目移動到容器的頂部或底部。

<div class="d-flex align-items-start flex-column bd-highlight mb-3" style="height: 200px;">
<div class="mb-auto p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex align-items-end flex-column bd-highlight mb-3" style="height: 200px;">
<div class="p-2 bd-highlight">Flex item</div>
<div class="p-2 bd-highlight">Flex item</div>
<div class="mt-auto p-2 bd-highlight">Flex item</div>
</div>

換行

改變Flex項目在Flex容器中換行的方式。可以選擇使用.flex-nowrap完全不換行（瀏覽器預設），使用.flex-wrap進行換行，或使用.flex-wrap-reverse進行反向換行。

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

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

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

flex-wrap也包含響應式變化。

• .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

排序

使用order通用類別改變特定flex項目顯示的排序。Bootstrap僅提供選項將一個物件排在第一個或最后一個，以及重置以使用DOM排序。由于order只能使用從0到5的整數值，任何額外值則需要自定義的CSS。

<div class="d-flex flex-nowrap bd-highlight">
<div class="order-3 p-2 bd-highlight">First flex item</div>
<div class="order-2 p-2 bd-highlight">Second flex item</div>
<div class="order-1 p-2 bd-highlight">Third flex item</div>
</div>

order也包含的響應式屬性。

• .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

此外還有響應式的.order-first和.order-last類別，它們分別透過order: -1和order: 6，來更改元素的order順序。

• .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

對齊內容

使用flexbox容器上的align-content通用類別將flex項目一起對齊于橫軸上。從start（瀏覽器預設）、end、center、between、around，或stretch中選擇。以下為了呈現這通用類別的效果，我們強制執行flex-wrap: wrap并增加了Flex項目的數量。

注意！ 此特性對于單行的Flex項目沒有作用。

<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也包含響應式變化。

• .align-content-start
• .align-content-end
• .align-content-center
• .align-content-around
• .align-content-stretch
• .align-content-sm-start
• .align-content-sm-end
• .align-content-sm-center
• .align-content-sm-around
• .align-content-sm-stretch
• .align-content-md-start
• .align-content-md-end
• .align-content-md-center
• .align-content-md-around
• .align-content-md-stretch
• .align-content-lg-start
• .align-content-lg-end
• .align-content-lg-center
• .align-content-lg-around
• .align-content-lg-stretch
• .align-content-xl-start
• .align-content-xl-end
• .align-content-xl-center
• .align-content-xl-around
• .align-content-xl-stretch
• .align-content-xxl-start
• .align-content-xxl-end
• .align-content-xxl-center
• .align-content-xxl-around
• .align-content-xxl-stretch

媒體對象

要從Bootstrap5復制媒體對象組件嗎？用一些flex實用程序很快就可以重新創建它，這些實用程序比以前更加靈活和定制。

<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>

And say you want to vertically center the content next to the image:

<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

Utilities API

Flexbox utilities are declared in our utilities API in scss/_utilities.scss.

    "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
),
"gap": (
responsive: true,
property: gap,
class: gap,
values: $spacers
),
"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,
),
),