Helper class to add car app extensions to notifications.
By default, notifications in a car screen have the properties provided by
NotificationCompat.Builder. This helper class provides methods to
override those properties for the car screen. However, notifications only show up in the car
screen if it is extended with
CarAppExtender, even if the extender does not override any
properties. To create a notification with car extensions:
- Create a
NotificationCompat.Builder, setting any desired properties.
- Create a
- Set car-specific properties using the
- Create a
NotificationCompat.Builder.extend(NotificationCompat.Extender)to apply the extensions to a notification.
- Post the notification to the notification system with the
CarNotificationManager.notify(...)methods. Do not use the
NotificationManager.notify(...), nor the NotificationManagerCompat.notify(...)} methods.
Notification notification = new NotificationCompat.Builder(context) ... .extend(new CarAppExtender.Builder() .set*(...) .build()) .build();
Car extensions can be accessed on an existing notification by using the
CarAppExtender(Notification) constructor, and then using the
get methods to access
The car screen UI is affected by the notification channel importance (Android O and above) or notification priority (below Android O) in the following ways:
- A heads-up-notification (HUN) will show if the importance is set to
NotificationManagerCompat.IMPORTANCE_HIGH, or the priority is set to
- The notification center icon, which opens a screen with all posted notifications when
tapped, will show a badge for a new notification if the importance is set to
NotificationManagerCompat.IMPORTANCE_DEFAULTor above, or the priority is set to
- The notification entry will show in the notification center for all priority levels.
CarAppExtender.Builder.setImportance(int)will override the importance for the notification in the car screen.
NotificationCompat.Builder#setOnlyAlertOnce(true) will alert a high-priority
notification only once in the HUN. Updating the same notification will not trigger another HUN
For a navigation app's turn-by-turn (TBT) notifications, which update the same notification
frequently with navigation information, the notification UI has a slightly different behavior.
The app can post a TBT notification by calling
TBT notifications behave the same as regular notifications with the following exceptions:
- The notification will not be displayed if the navigation app is not the currently active navigation app, or if the app is already displaying routing information in the navigation template.
- The heads-up-notification (HUN) can be customized with a background color through
- The notification will not be displayed in the notification center.
In addition to that, the information in the navigation notification will be displayed in the rail widget at the bottom of the screen when the app is in the background.
Note that frequent HUNs distract the driver. The recommended practice is to update the TBT
notification regularly on distance changes, which updates the rail widget, but call
NotificationCompat.Builder#setOnlyAlertOnce(true) unless there is a significant navigation turn