Voice assistant Tap-to-Read

Android Automotive considers voice to be a crucial component for drive-safe interactions and one of the safest ways for users to interact with the Android Automotive OS while driving. As a result, we expanded the Android voice assistant APIs (including VoiceInteractionSession) to enable voice assistants to perform tasks for users that can be difficult to accomplish while driving.

Tap-to-Read enables voice assistants to read and reply to text messages on behalf of the user, when the user interacts with message notifications. To provide this functionality, you can integrate a voice assistant with CarVoiceInteractionSession.

In Automotive, notifications posted to the Notification Center identified as INBOX or INBOX_IN_GROUP (for example, SMS messages) include a Play button. The user can click Play to have the selected voice assistant read the notification aloud, and to optionally reply by voice.

Figure 1. Tap-to-Read notification with Play button.

Integrate with CarVoiceInteractionSession

The next sections describe how to integrate a voice assistant with CarVoiceInteractionSession.

Support voice interactions

Apps that provide car voice interaction services must integrate with the existing Android voice interactions. To learn more, see Google Assistant for Android (with the exception of VoiceInteractionSession). While all voice interaction API elements remain the same as implemented on mobile devices, CarVoiceInteractionSession (described in Implement CarVoiceInteractionSession) replaces VoiceInteractionSession. For more information, see these pages:

• VoiceInteractionSession
• Implementing Your Own Assistant

Implement CarVoiceInteractionSession

CarVoiceInteractionSession exposes APIs that you can use to enable voice assistants to read text messages aloud and then reply to theose messages on behalf of the user.

The key difference between the CarVoiceInteractionSession and VoiceInteractionSession classes is that CarVoiceInteractionSession passes in the action in onShow so the voice assistant can detect the context of the user's request as soon as CarVoiceInteractionSession starts a session. The parameters for onShow for each class are listed in the following table:

CarVoiceInteractionSession	VoiceInteractionSession
onShow takes these three parameters: args showFlags actions	onShow takes these two parameters: args showFlags

Note: If no action is specified, VOICE_ACTION_NO_ACTION is passed in.

Changes in Android 10

Starting with Android 10, the platform calls VoiceInteractionService.onGetSupportedVoiceActions to detect which actions are supported. The voice assistant overrides and implements VoiceInteractionService.onGetSupportedVoiceActions, as shown in the following example:

public class MyInteractionService extends VoiceInteractionService {
    private static final List SUPPORTED_VOICE_ACTIONS = Arrays.asList(
        CarVoiceInteractionSession.VOICE_ACTION_READ_NOTIFICATION);

    @Override
    public Set onGetSupportedVoiceActions(@NonNull Set voiceActions) {
       Set result = new HashSet<>(voiceActions);
       result.retainAll(SUPPORTED_VOICE_ACTIONS);
       return result;
   }
}

Valid actions are described in the following table. For details about each action, see Sequence diagrams.

Action	Expected payload	Expected voice interaction action
VOICE_ACTION_READ_NOTIFICATION	Read messages aloud to the user and then fire the Mark as Read pending intent back when the messages are read successfully. Optionally, prompt the user for a reply.
VOICE_ACTION_REPLY_NOTIFICATION	Parcelable with key. KEY_NOTIFICATION that maps to StatusBarNotification. Requires android.permission.BIND_NOTIFICATION_LISTENER_SERVICE.	Prompt the user to state the reply message, input the reply message into the RemoteInputReply of the pending intent, and then fire the pending intent.
VOICE_ACTION_HANDLE_EXCEPTION	String with key. KEY_EXCEPTION that maps to ExceptionValue (described in Exception values). KEY_FALLBACK_ASSISTANT_ENABLED that maps to a Boolean value. If the value is true, the fallback assistant that can handle the user's request has been disabled.	The expected action to be taken for the exception is defined in the documentation for the exception.

Exception values

EXCEPTION_NOTIFICATION_LISTENER_PERMISSIONS_MISSING indicates to the voice assistant that it's missing the Manifest.permission.BIND_NOTIFICATION_LISTENER_SERVICE permission and to get this permission from the user.

Request notification listener permission

If the default voice assistant doesn't have the notification listener permission, the platform's FallbackAssistant (if enabled by the car manufacturer) might read the message aloud before the voice assistant is notifed to request the permission. To determine if FallbackAssistant is enabled and has read the message, the voice assistant should check the KEY_FALLBACK_ASSISTANT_ENABLED Boolean value in the payload.

The platform recommends the voice assistant add rate-limiting logic for the number of times this permission is requested. Doing so respects the user who doesn't want to grant the voice assistant this permission and prefers the FallbackAssistant to read text messages aloud. Prompting a user for permission each time the user presses Play on a message notification can be a negative user experience. The platform doesn't impose rate limits on behalf of the voice assistant.

When requesting the notification listener permission, the voice assistant should use CarUxRestrictionsManager to determine if a user is parked or is driving. If the user is driving, the voice assistant displays a notification that provides instructions on how to grant the permission. Doing so helps (and reminds) the user to grant the permission when it's safer.

Work with StatusBarNotification

StatusBarNotification passed in with the Read and Reply voice actions are always in a car-compatible messaging notification as described in Notify users of messages. While some notifications might not have the Reply Pending intent, they all have Mark as Read pending intents.

To streamline interactions with notifications, use NotificationPayloadHandler, which provides methods to extract messages from the notification and write the reply messages to the appropriate pending intent of the notification. After the voice assistant reads the message, the voice assistant must fires the Mark as Read intent.

Satisfy Tap-to-Read preconditions

Only VoiceInteractionSession of the default voice assistant is notified when a user triggers the voice action to read and reply to messages. As mentioned above, this default voice assistant must also have the notification listener permission.

Sequence diagrams

These figures display the logic flows of CarVoiceInteractionSession actions:

Figure 2. Sequence diagram for VOICE_ACTION_READ_NOTIFICATION.

In the case of Figure 3, the app of rate limits on permission requests is recommended:

Figure 3. Sequence diagram for VOICE_ACTION_REPLY_NOTIFICATION.

Figure 4. Sequence diagram for VOICE_ACTION_HANDLE_EXCEPTION.

Read name of app

If you want your voice assistant to read the messaging app's name aloud during the message readout (for example, "Sam from Hangouts said..."), create a function like that shown in the following code example to ensure the assistant is reading the correct name:

@Nullable
String getMessageApplicationName(Context context, StatusBarNotification statusBarNotification) {
    ApplicationInfo info = getApplicationInfo(context, statusBarNotification.getPackageName());
    if (info == null) return null;

    Notification notification = statusBarNotification.getNotification();

    // Sometimes system packages will post on behalf of other apps, so check this
    // field for a system app notification.
    if (isSystemApp(info)
            && notification.extras.containsKey(Notification.EXTRA_SUBSTITUTE_APP_NAME)) {
        return notification.extras.getString(Notification.EXTRA_SUBSTITUTE_APP_NAME);
    } else {
        PackageManager pm = context.getPackageManager();
        return String.valueOf(pm.getApplicationLabel(info));
    }
}

@Nullable
ApplicationInfo getApplicationInfo(Context context, String packageName) {
    final PackageManager pm = context.getPackageManager();
    ApplicationInfo info;
    try {
        info = pm.getApplicationInfo(packageName, 0);
    } catch (PackageManager.NameNotFoundException e) {
        return null;
    }
    return info;
}

boolean isSystemApp(ApplicationInfo info) {
    return (info.flags & ApplicationInfo.FLAG_SYSTEM) != 0;
}