example of AlwaysOnHotwordDetector in Android

Unless I have a huge blind spot, I don't think third-party applications can make use of this API. Its strange that AlwaysOnHotwordDetector (and related classes VoiceInteractionService etc.) have been granted public access.

If you are building a privileged app, look through these test projects from AOSP:

• Voice Interaction - Basic AlwaysOnHotwordDetector usage/implementation http://androidxref.com/5.0.0_r2/xref/frameworks/base/tests/VoiceInteraction/
• Voice Enrollment - http://androidxref.com/5.0.0_r2/xref/frameworks/base/tests/VoiceEnrollment/

While trying to make this work, I came upon this:

AlwaysOnHotwordDetector's constructor:

/** * @param text The keyphrase text to get the detector for. * @param locale The java locale for the detector. * @param callback A non-null Callback for receiving the recognition events. * @param voiceInteractionService The current voice interaction service. * @param modelManagementService A service that allows management of sound models. * * @hide */public AlwaysOnHotwordDetector(String text, Locale locale, Callback callback,        KeyphraseEnrollmentInfo keyphraseEnrollmentInfo,        IVoiceInteractionService voiceInteractionService,        IVoiceInteractionManagerService modelManagementService) {    mText = text;    mLocale = locale;    mKeyphraseEnrollmentInfo = keyphraseEnrollmentInfo;    mKeyphraseMetadata = mKeyphraseEnrollmentInfo.getKeyphraseMetadata(text, locale);    mExternalCallback = callback;    mHandler = new MyHandler();    mInternalCallback = new SoundTriggerListener(mHandler);    mVoiceInteractionService = voiceInteractionService;    mModelManagementService = modelManagementService;    new RefreshAvailabiltyTask().execute();}

The statement of interest here is:

mKeyphraseMetadata = mKeyphraseEnrollmentInfo.getKeyphraseMetadata(text, locale);

What does KeyphraseEnrollmentInfo#getKeyphraseMetadata(String, Locale) do?

/** * Gets the {@link KeyphraseMetadata} for the given keyphrase and locale, null if any metadata * isn't available for the given combination. * * @param keyphrase The keyphrase that the user needs to be enrolled to. * @param locale The locale for which the enrollment needs to be performed. *        This is a Java locale, for example "en_US". * @return The metadata, if the enrollment client supports the given keyphrase *         and locale, null otherwise. */public KeyphraseMetadata getKeyphraseMetadata(String keyphrase, Locale locale) {    if (mKeyphrases == null || mKeyphrases.length == 0) {        Slog.w(TAG, "Enrollment application doesn't support keyphrases");        return null;    }    for (KeyphraseMetadata keyphraseMetadata : mKeyphrases) {        // Check if the given keyphrase is supported in the locale provided by        // the enrollment application.        if (keyphraseMetadata.supportsPhrase(keyphrase)                && keyphraseMetadata.supportsLocale(locale)) {            return keyphraseMetadata;        }    }    Slog.w(TAG, "Enrollment application doesn't support the given keyphrase/locale");    return null;}

At this point, my example project kept telling me: Enrollment application doesn't support keyphrases. So, digging a bit further - to support keyphrases, we need to provide additional meta-data:

// Taken from class KeyphraseEnrollmentInfo/** * Name under which a Hotword enrollment component publishes information about itself. * This meta-data should reference an XML resource containing a * <code><{@link * android.R.styleable#VoiceEnrollmentApplication * voice-enrollment-application}></code> tag. */private static final String VOICE_KEYPHRASE_META_DATA = "android.voice_enrollment";

Additionally, we will need the android.permission.MANAGE_VOICE_KEYPHRASES permission. This is where the example project gets stuck:

<!-- Must be required by hotword enrollment application,     to ensure that only the system can interact with it.     @hide <p>Not for use by third-party applications.</p> --><permission android:name="android.permission.MANAGE_VOICE_KEYPHRASES"    android:label="@string/permlab_manageVoiceKeyphrases"    android:description="@string/permdesc_manageVoiceKeyphrases"    android:protectionLevel="signature|system" />

The permission required to support hotword detection is not available to third-party applications. I still can't figure out why package android.service.voice package has public access. Perhaps I am missing something here.