在这份指南中你将了解到把一个盒子居中放置在另一个之中的方法。在伸缩盒子模型(flexbox)出现之前，要做到同时垂直与水平居中是很困难的，而现在利用盒子对齐属性(Box Alignment)就很直截了当了。
需求
把一个项目同时垂直与水平居中地放置在一个盒子中
指南
做出选择
要将一个盒子居中放置在另一个之中，我们需要让作为容器的盒子变成伸缩容器。再将 align-items 设置为 center 来实现块方向的轴(block axis)上的居中，并把 justify-content 设置为 center 来实现文字方向的轴(inline axis)上的居中。
将来我们可能不需要将父容器设置为伸缩容器就可以居中元素，因为此处使用的“盒子对齐”属性也被指定为适用于块布局。然而，当前在块布局上对盒子对齐属性的支持仍然是有限的，因此目前使用伸缩盒子来实现居中还是最可靠的方法。
浏览器兼容性
各种布局方法具有不同的浏览器支持。有关所使用属性的基本支持的详细信息，请参见下表
align-items
Update compatibility data on GitHub | Desktop | Mobile |
|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet |
|---|
| Supported in Flex Layout | Chrome
Full support
52-
Full support
52
-
Partial support
29
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
21
- Prefixed Implemented with the vendor prefix: -webkit-
| Edge
Full support
12-
Full support
12
-
Full support
12
- Prefixed Implemented with the vendor prefix: -webkit-
| Firefox
Full support
20-
Full support
20
- Notes Multi-line flexbox has been supported since Firefox 28.
-
Full support
49
- Prefixed Implemented with the vendor prefix: -webkit-
-
No support
18 — 20
- Disabled From version 18 until version 20 (exclusive): this feature is behind the
layout.css.flexbox.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config. -
Full support
48
- Prefixed Implemented with the vendor prefix: -webkit-
- Disabled From version 48: this feature is behind the
layout.css.prefixes.webkit preference (needs to be set to true). To change preferences in Firefox, visit about:config.
| IE
Full support
11-
Full support
11
- Notes In Internet Explorer 10 and 11, if column flex items have
align-items: center; set on them and their content is too large, then they will overflow the bounds of their container. See Flexbug #2.
| Opera
Full support
12.1 | Safari
Full support
9-
Full support
9
-
Full support
7
- Prefixed Implemented with the vendor prefix: -webkit-
| WebView Android
Full support
52-
Full support
52
-
Partial support
4.4
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
≤37
- Prefixed Implemented with the vendor prefix: -webkit-
| Chrome Android
Full support
52-
Full support
52
-
Partial support
29
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
25
- Prefixed Implemented with the vendor prefix: -webkit-
| Firefox Android
Full support
20-
Full support
20
- Notes Multi-line flexbox has been supported since Firefox 28.
-
Full support
49
- Prefixed Implemented with the vendor prefix: -webkit-
-
No support
18 — 20
- Disabled From version 18 until version 20 (exclusive): this feature is behind the
layout.css.flexbox.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config. -
Full support
48
- Prefixed Implemented with the vendor prefix: -webkit-
- Disabled From version 48: this feature is behind the
layout.css.prefixes.webkit preference (needs to be set to true). To change preferences in Firefox, visit about:config.
| Opera Android
Full support
12.1 | Safari iOS
Full support
9-
Full support
9
-
Full support
7
- Prefixed Implemented with the vendor prefix: -webkit-
| Samsung Internet Android
Full support
6.0-
Full support
6.0
-
Partial support
2.0
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Samsung Internet 6.0.
-
Full support
1.5
- Prefixed Implemented with the vendor prefix: -webkit-
|
|---|
| Supported in Grid Layout | Chrome
Full support
57 | Edge
Full support
16 | Firefox
Full support
52 | IE
No support
No | Opera
Full support
44 | Safari
Full support
10.1 | WebView Android
Full support
57 | Chrome Android
Full support
52 | Firefox Android
Full support
52 | Opera Android
Full support
43 | Safari iOS
Full support
10.3 | Samsung Internet Android
Full support
6.2 |
|---|
Legend
-
Full support
- Full support
-
No support
- No support
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.
- Requires a vendor prefix or different name for use.
- Requires a vendor prefix or different name for use.
justify-content
Update compatibility data on GitHub | Desktop | Mobile |
|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet |
|---|
| Supported in Flex Layout | Chrome
Full support
52-
Full support
52
-
Partial support
29
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
21
- Prefixed Implemented with the vendor prefix: -webkit-
| Edge
Full support
12-
Full support
12
-
Full support
12
- Prefixed Implemented with the vendor prefix: -webkit-
| Firefox
Full support
20-
Full support
20
- Notes Before Firefox 27, Firefox supported only single-line flexbox.
-
No support
18 — 20
- Disabled From version 18 until version 20 (exclusive): this feature is behind the
layout.css.flexbox.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config. -
Full support
49
- Prefixed Implemented with the vendor prefix: -webkit-
-
Full support
48
- Prefixed Implemented with the vendor prefix: -webkit-
- Disabled From version 48: this feature is behind the
layout.css.prefixes.webkit preference (needs to be set to true). To change preferences in Firefox, visit about:config.
| IE
Full support
11 | Opera
Full support
12.1 | Safari
Full support
9-
Full support
9
-
Full support
6.1
- Prefixed Implemented with the vendor prefix: -webkit-
| WebView Android
Full support
52-
Full support
52
-
Partial support
4.4
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
≤37
- Prefixed Implemented with the vendor prefix: -webkit-
| Chrome Android
Full support
52-
Full support
52
-
Partial support
29
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
25
- Prefixed Implemented with the vendor prefix: -webkit-
| Firefox Android
Full support
20-
Full support
20
- Notes Before Firefox 27, Firefox supported only single-line flexbox.
-
No support
18 — 20
- Disabled From version 18 until version 20 (exclusive): this feature is behind the
layout.css.flexbox.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config. -
Full support
49
- Prefixed Implemented with the vendor prefix: -webkit-
-
Full support
48
- Prefixed Implemented with the vendor prefix: -webkit-
- Disabled From version 48: this feature is behind the
layout.css.prefixes.webkit preference (needs to be set to true). To change preferences in Firefox, visit about:config.
| Opera Android
Full support
12.1 | Safari iOS
Full support
9-
Full support
9
-
Full support
6.1
- Prefixed Implemented with the vendor prefix: -webkit-
| Samsung Internet Android
Full support
6.0-
Full support
6.0
-
Partial support
2.0
- Notes Older versions of the specification treat absolute positioned children as though they are a 0 by 0 flex item. Later specification versions take the children out of the flow and set their positions based on align and justify properties. Chrome implements the new behavior beginning with Chrome 52.
-
Full support
1.5
- Prefixed Implemented with the vendor prefix: -webkit-
|
|---|
| Supported in Grid Layout | Chrome
Full support
57 | Edge
Full support
16 | Firefox
Full support
52 | IE
No support
No | Opera
Full support
44 | Safari
Full support
10.1 | WebView Android
Full support
57 | Chrome Android
Full support
52 | Firefox Android
Full support
52 | Opera Android
Full support
43 | Safari iOS
Full support
10.3 | Samsung Internet Android
Full support
6.2 |
|---|
Legend
-
Full support
- Full support
-
No support
- No support
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.
- Requires a vendor prefix or different name for use.
- Requires a vendor prefix or different name for use.
MDN上相关的资源