material-components_material-components-android/docs/components/BadgeDrawable.md

BadgeDrawable

Using badges

Badge	Badge with number	Badge with a maximum character count

Note: This component is still under development and may not support the full range of customization Material Android components generally support, for instance, themed attributes.

A BadgeDrawable represents dynamic information such as a number of pending requests in a BottomNavigationView or TabLayout.

Design & API Documentation

• Material Design guidelines: Bottom Navigation
• Class definition
• Class overview

Usage

Create an instance of BadgeDrawable by calling create(Context) or createFromAttributes(Context, AttributeSet, int, int)}.

The approach used to add and display a BadgeDrawable on top of its anchor view depends on the API level:

In API 18+ (APIs supported by ViewOverlay)

1. Add BadgeDrawable as a ViewOverlay to the desired anchor view.
2. Update the BadgeDrawable's coordinates (center and bounds) based on its anchor view using #updateBadgeCoordinates(View).

Both steps have been encapsulated in a util method:

BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor);

In Pre API-18

1. Set BadgeDrawable as the foreground of the anchor view's FrameLayout ancestor.
2. Update the BadgeDrawable's coordinates (center and bounds) based on its anchor view, relative to its FrameLayout ancestor's coordinate space.

Option 1: BadgeDrawable will dynamically create and wrap the anchor view in a FrameLayout, then insert the FrameLayout into the original anchor view position in the view hierarchy. Same syntax as API 18+

BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor);

Option 2: If you do not want BadgeDrawable to modify your view hierarchy, you can specify a FrameLayout to display the badge instead.

* BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor, anchorFrameLayoutParent);

BadgeDrawable Gravity Modes

BadgeDrawable provides four pre-packaged gravity modes that control how the badge aligns with its anchor view. By default (TOP_END) badge aligns with the top and end edges of the anchor (with some offsets). The other options are TOP_START, BOTTOM_START and BOTTOM_END.

BadgeDrawable center offsets

By default, BadgeDrawable is aligned with the top and end edges of its anchor view (with some offsets). Call setBadgeGravity(int) to change it to one of the other supported modes. To adjust the badge's offsets relative to the anchor's center, use setHoriziontalOffset(int) or setVerticalOffset(int)

BadgeDrawable Attributes

Feature	Relevant attributes
Color	app:backgroundColor app:badgeTextColor
Label	app:number
Label Length	app:maxCharacterCount
Badge Gravity	app:badgeGravity

Talkback Support

BadgeDrawable provides a getter for its content description, which is based on the number (if any) displayed. Users should specify content description: setContentDescriptionNumberless(CharSequence) setContentDescriptionQuantityStringsResource(@StringRes)