Material Chip button semantics

Flutter now applies the semantic label of button to all interactive Material Chips for accessibility purposes.

Interactive Material Chips (namely ActionChip, ChoiceChip, FilterChip, and InputChip) are now semantically marked as being buttons. However, the non-interactive information Chip is not.

Marking Chips as buttons helps accessibility tools, search engines, and other semantic analysis software understand the meaning of an app. For example, it allows screen readers (such as TalkBack on Android and VoiceOver on iOS) to announce a tappable Chip as a "button", which can assist users in navigating your app. Prior to this change, users of accessibility tools may have had a subpar experience, unless you implemented a workaround by manually adding the missing semantics to the Chip widgets in your app.

The outermost Semantics widget that wraps all Chip classes to describe their semantic properties is modified.

The following changes apply to ActionChip, ChoiceChip, FilterChip, and InputChip:

• The button property is set to true.
• The enabled property reflects whether the Chip is currently tappable (by having a callback set).

These property changes bring interactive Chips' semantic behavior in-line with that of other Material Buttons.

For the non-interactive information Chip:

• The button property is set to false.
• The enabled property is set to null.

You might not need to perform any migration. This change only affects you if you worked around the issue of Material Chips missing button semantics by wrapping the widget given to the label field of a Chip with a Semantics widget marked as button: true. In this case, the inner and outer button semantics conflict, resulting in the tappable area of the button shrinking down to the size of the label after this change is introduced. Fix this issue either by deleting that Semantics widget and replacing it with its child, or by removing the button: true property if other semantic properties still need to be applied to the label widget of the Chip.

The following snippets use InputChip as an example, but the same process applies to ActionChip, ChoiceChip, and FilterChip as well.

Case 1: Remove the Semantics widget.

Code before migration:

Widget myInputChip = InputChip(
  onPressed: () {},
  label: Semantics(
    button: true,
    child: Text('My Input Chip'),
  ),
);

Code after migration:

Widget myInputChip = InputChip(
  onPressed: () {},
  label: Text('My Input Chip'),
);

Case 2: Remove button:true from the Semantics widget.

Code before migration:

Widget myInputChip = InputChip(
  onPressed: () {},
  label: Semantics(
    button: true,
    hint: 'Example Hint',
    child: Text('My Input Chip'),
  ),
);

Code after migration:

Widget myInputChip = InputChip(
  onPressed: () {},
  label: Semantics(
    hint: 'Example Hint',
    child: Text('My Input Chip'),
  ),
);

Landed in version: 1.23.0-7.0.pre
In stable release: 2.0.0

API documentation:

• ActionChip
• Chip
• ChoiceChip
• FilterChip
• InputChip
• Material Buttons
• Material Chips
• Semantics
• SemanticsProperties.button
• SemanticsProperties.enabled

Relevant issue:

• Issue 58010: InputChip doesn't announce any action for a11y on iOS

Relevant PRs:

• PR 60141: Tweaking Material Chip a11y semantics to match buttons
• PR 60645: Revert "Tweaking Material Chip a11y semantics to match buttons (#60141)
• PR 61048: Re-land "Tweaking Material Chip a11y semantics to match buttons (#60141)

除非另有说明，本文档之所提及适用于 Flutter 的最新稳定版本，本页面最后更新时间: 2024-04-04。 查看文档源码 或者 为本页面内容提出建议。