звукът на канала за уведомяване на android не работи

Първо не знам Вашето известие не работи на кои устройства като Oreo, Pie или по-ниски от N.

For your question StackOver Flow have lots of answer.

Сега според въпроса ви липсва само един ред код, но тук не можете да проверите целия си код за уведомяване, защото все още не сте поставили.

Тук поставям код за уведомяване, който просто изпълнява всичките ви изисквания за уведомяване. (Пълно персонализирано известие)

Известие с изображение

public void createNotificationWithImage(String title,String message ,Bitmap image) {
PendingIntent resultPendingIntent = PendingIntent.getActivity(mContext,
            0 /* Request code */, resultIntent,
            PendingIntent.FLAG_UPDATE_CURRENT);

// Custom Sound Uri

Uri soundUri = Uri.parse("android.resource://" + mContext.getApplicationContext()
                .getPackageName() + "/" + R.raw.sniper_gun);

 mBuilder = new NotificationCompat.Builder(mContext);
 mBuilder.setSmallIcon(R.mipmap.notification_icon);

 // Pay attention on below line here (NOTE)
 mBuilder.setSound(soundUri);

if (image!=null) {
            mBuilder.setContentTitle(title)
                    .setContentText(message)
                    .setAutoCancel(false)
                    .setLargeIcon(image)
                    .setStyle(new NotificationCompat.BigPictureStyle()
                            .bigPicture(image).setSummaryText(message).bigLargeIcon(null))
                    .setColor(Color.GREEN)
                    .setContentIntent(resultPendingIntent);
        }
mNotificationManager = (NotificationManager) mContext.getSystemService(Context.NOTIFICATION_SERVICE);

Сега поставям код за известяване, който ще работи над или на устройства OREO.

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
        int importance = NotificationManager.IMPORTANCE_HIGH;
        NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "NOTIFICATION_CHANNEL_NAME", importance);
        notificationChannel.enableLights(true);
        notificationChannel.setLightColor(Color.RED);
        notificationChannel.enableVibration(true);
        notificationChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});

        if(soundUri != null){
            AudioAttributes audioAttributes = new AudioAttributes.Builder()
                    .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                    .setUsage(AudioAttributes.USAGE_ALARM)
                    .build();
            notificationChannel.setSound(soundUri,audioAttributes);
        }

        assert mNotificationManager != null;
        mBuilder.setChannelId(NOTIFICATION_CHANNEL_ID);
        mNotificationManager.createNotificationChannel(notificationChannel);
    }
    assert mNotificationManager != null;
    mNotificationManager.notify(0 /* Request Code */, mBuilder.build());


below middle braces use for close your method.
}

Известие за без изображение

    public void createNotification(String title,String message){
    PendingIntent resultPendingIntent = PendingIntent.getActivity(mContext,
                0 /* Request code */, resultIntent,
                PendingIntent.FLAG_UPDATE_CURRENT);

        Uri soundUri = Uri.parse("android.resource://" + mContext.getApplicationContext()
                .getPackageName() + "/" + R.raw.sniper_gun);



        mBuilder = new NotificationCompat.Builder(mContext);
        mBuilder.setSmallIcon(R.mipmap.notification_icon);
        mBuilder.setLargeIcon(BitmapFactory.decodeResource(mContext.getResources(),
                R.mipmap.icon));
        mBuilder.setSound(soundUri);
        mBuilder.setContentTitle(title)
                .setContentText(message)
                .setAutoCancel(false)
                .setColor(Color.GREEN)
                .setStyle(new NotificationCompat.BigTextStyle())
                .setContentIntent(resultPendingIntent);

        mNotificationManager = (NotificationManager) mContext.getSystemService(Context.NOTIFICATION_SERVICE);

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            int importance = NotificationManager.IMPORTANCE_HIGH;
            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "NOTIFICATION_CHANNEL_NAME", importance);
            notificationChannel.enableLights(true);
            notificationChannel.setLightColor(Color.RED);
            notificationChannel.enableVibration(true);
            notificationChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
//            notificationChannel.s

            if(soundUri != null){
                AudioAttributes audioAttributes = new AudioAttributes.Builder()
                        .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                        .setUsage(AudioAttributes.USAGE_ALARM)
                        .build();
                notificationChannel.setSound(soundUri,audioAttributes);
            }

            assert mNotificationManager != null;
            mBuilder.setChannelId(NOTIFICATION_CHANNEL_ID);
            mNotificationManager.createNotificationChannel(notificationChannel);

        }

        assert mNotificationManager != null;
        mNotificationManager.notify(0 /* Request Code */, mBuilder.build());

    }

ЗАБЕЛЕЖКА: В моя код споменах, че трябва да обърнете внимание на един конкретен ред, където описах да задам звуков Uri с известие. Можете да опишете така.

mBuilder.setContentTitle(title)
            .setContentText(message)
            .setAutoCancel(false)
            .setSound(soundUri)
            .setColor(Color.GREEN)
            .setStyle(new NotificationCompat.BigTextStyle())
            .setContentIntent(resultPendingIntent);

но няма да възпроизведе звук за вашето устройство, тъй като след устройството Oreo звукът не е зададен като ниво на приоритет.

Така че винаги за звук използвайте кода, както описах.

предполагам, че използвате грешен тип употреба, моля, редактирайте вашата audioAttributes употреба на USAGE_NOTIFICATION

            val audioAttributes = AudioAttributes.Builder()
            .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
            .setUsage(AudioAttributes.USAGE_NOTIFICATION)
            .build()

От официалния документ:

USAGE_NOTIFICATION : Стойност на употреба, която да се използва, когато употребата е известие.

Трябва да използвате аудио атрибути и също трябва да дефинирате URI на мелодията с разрешение.

Така че първо дефинираме URI адреса на мелодията:

Uri ringtoneUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
boolean vibrate = true;
long[] vibratePattern = new long[]{0L, 1000L};



public constructor(){
 notificationBuilder = new NotificationCompat.Builder(mContext, app.getAppContext().getString(R.string.default_notification_channel_id));
        mNotifyManager = (NotificationManager) mContext.getSystemService(Context.NOTIFICATION_SERVICE);
        mContext.grantUriPermission("com.android.systemui", ringtoneUri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
}
 public void showNotificationNormal(String notificationTitle, String notificationBody, Intent intent) {
    String id = mContext.getString(R.string.default_notification_channel_id);
    PendingIntent lowIntent = PendingIntent.getActivity(mContext, 100, intent, PendingIntent.FLAG_CANCEL_CURRENT);
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(mContext, id);
    NotificationManager mNotifyManager = (NotificationManager) mContext.getSystemService(Context.NOTIFICATION_SERVICE);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = mContext.getString(R.string.default_notification_channel_name);
        String description = mContext.getString(R.string.default_notification_channel_description); //user visible
        int importance = NotificationManager.IMPORTANCE_HIGH;

        AudioAttributes att = new AudioAttributes.Builder()
                .setUsage(AudioAttributes.USAGE_NOTIFICATION)
                .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                .build();

        NotificationChannel mChannel = new NotificationChannel(id, name, importance);
        mChannel.setDescription(description);
        mChannel.enableLights(true);
        mChannel.enableVibration(vibrate);
        mChannel.setVibrationPattern(vibratePattern);
        mChannel.setLightColor(Color.RED);
        mChannel.setSound(ringtoneUri, att);
        mChannel.setBypassDnd(true);
        mChannel.setLockscreenVisibility(NotificationCompat.VISIBILITY_PUBLIC);
        mChannel.setShowBadge(true);

        if (mNotifyManager != null) {
            mNotifyManager.createNotificationChannel(mChannel);
        }

        notificationBuilder
                .setSmallIcon(R.mipmap.ic_launcher)
                .setPriority(NotificationCompat.PRIORITY_MAX)
                .setCategory(NotificationCompat.CATEGORY_MESSAGE)
                .setVibrate(vibratePattern)
                .setSound(ringtoneUri)
                .setColor(ContextCompat.getColor(mContext, R.color.colorPrimary))
                .setContentTitle(notificationTitle)
                .setStyle(new NotificationCompat.BigTextStyle().bigText(notificationBody))
                .setAutoCancel(true)
                .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)
                .setContentIntent(lowIntent);

    } else {
        notificationBuilder.setContentTitle(notificationTitle)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setPriority(NotificationCompat.PRIORITY_MAX)
                .setCategory(NotificationCompat.CATEGORY_MESSAGE)
                .setVibrate(vibratePattern)
                .setSound(ringtoneUri)
                .setStyle(new NotificationCompat.BigTextStyle().bigText(notificationBody))
                .setColor(ContextCompat.getColor(mContext, R.color.colorPrimary))
                .setAutoCancel(true)
                .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)
                .setContentIntent(lowIntent);

    }

    notificationBuilder.setContentText(notificationBody);

    if (mNotifyManager != null) {
        mNotifyManager.notify(AppConstants.NOTIFY_ID, notificationBuilder.build());
    }
}