Flex
flexbox 通用類別的套件包管理網格欄的排版、對齊、尺寸縮放,以及導覽、元件等。對於更複雜的表現則需要自訂 CSS。
啟用 flex
使用 display
通用類別來創建一個 flexbox 容器,並將 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
方向性
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
對齊物件
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
填滿
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),同時佔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。在下面的範例中,.flex-grow-1
元素使用它可以使用的所有可用空間,同時允許剩餘的兩個 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。在下面的範例中,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” 以允許更多空間用於上一個帶有 .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
自動的 margins
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。下面的範例是透過自動 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
),並向左推兩個項目 (.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>
Wrap
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後一個,以及重置以使用 DOM 排序。由於 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 對齊於橫軸上。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
並增加了 Flex 項目的數量。
注意! 此特性對於單行的 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
Media object
想要從 Bootstrap 4 複製 media object 元件? 使用一些 flex 通用類別立即重新創建它,這些通用類別比以前擁有更多的靈活性與客製化。
<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>
假使你想將圖片旁邊的內容垂直置中:
<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
Utilities API
Flexbox 通用類別在 scss/_utilities.scss
中的 utilities API 中宣告。了解如何使用 utilities 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
),
"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,
),
),