Notification

/**
 * android 8.0 oreo의 경우 알림채널 설정해야 알림이 옴
 * - targetSDKVersion이 26버전보다 아래라면 문제없이 알림이 옴(version < 26)
 * - 채널은 한번만 만들면 되기때문에 Notification이 올때마다 만들어줄 필요가 없다.
 *   Application Class에서 만들어 줘 되고 SharedPreference를 이용해서 한번 만든적이 있다면
 *   그다음부터는 만들지 않도록 해주어도 된다.
 */

private void sendNotification(String title, String message) {
    int messageId = Integer.parseInt(PushUtils.getId());

    Intent intent = new Intent(this, MainActivity.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
            PendingIntent.FLAG_CANCEL_CURRENT);

    String channelId         = "FCMTestId";
    CharSequence channelName = "FCTMTestName";
    String description       = "FCMTest";
    NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) { // O = 26, O_MR1 = 27
        NotificationChannel notificationChannel = new NotificationChannel(channelId, channelName, NotificationManager.IMPORTANCE_DEFAULT);
        notificationChannel.setDescription(description);
        notificationChannel.enableLights(true);
        notificationChannel.enableVibration(true);
        notificationChannel.setVibrationPattern(new long[]{100,200,100,200});
        notificationChannel.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
        notificationManager.createNotificationChannel(notificationChannel);
    }

    Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, channelId)
            .setLargeIcon(BitmapFactory.decodeResource(getResources(), android.R.drawable.ic_dialog_info))
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle(title)
            .setContentText(message)
            .setAutoCancel(true) /*클릭시 해당 Notification만 제거*/
            .setSound(defaultSoundUri)
            .setPriority(Notification.PRIORITY_MAX) /*Priority 높여 알림 볼 수 있게 함*/
            .setContentIntent(pendingIntent);

    notificationManager.notify(messageId /* ID of notification */, notificationBuilder.build());
}