Failed to post notification on channel "null" Target Api is 26

Question

Two log showing

1: Use of stream types is deprecated for operations other than volume control

2: See the documentation of setSound() for what to use instead with android.media.AudioAttributes to qualify your playback use case

Answer 1

From the developer documentation:

When you target Android 8.0 (API level 26), you must implement one or more notification channels to display notifications to your users.

int NOTIFICATION_ID = 234;
NotificationManager notificationManager = (NotificationManager) ctx.getSystemService(Context.NOTIFICATION_SERVICE);
String CHANNEL_ID;
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    CHANNEL_ID = "my_channel_01";
    CharSequence name = "my_channel";
    String Description = "This is my channel";
    int importance = NotificationManager.IMPORTANCE_HIGH;
    NotificationChannel mChannel = new NotificationChannel(CHANNEL_ID, name, importance);
    mChannel.setDescription(Description);
    mChannel.enableLights(true);
    mChannel.setLightColor(Color.RED);
    mChannel.enableVibration(true);
    mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
    mChannel.setShowBadge(false);
    notificationManager.createNotificationChannel(mChannel);
}

NotificationCompat.Builder builder = new NotificationCompat.Builder(ctx, CHANNEL_ID)
    .setSmallIcon(R.mipmap.ic_launcher)
    .setContentTitle(title)
    .setContentText(message);

Intent resultIntent = new Intent(ctx, MainActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(ctx);
stackBuilder.addParentStack(MainActivity.class);
stackBuilder.addNextIntent(resultIntent);
PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(resultPendingIntent);
notificationManager.notify(NOTIFICATION_ID, builder.build());

One interesting thing to note: If a channel already exists, calling createNotificationChannel has no effect, so you can create all channels whenever you start your application.

Answer 2

Gulzar Bhat's answer is working perfectly if your minimum API is Oreo. If your minimum is lower however, you have to wrap the NotificationChannel code in a platform level check. After that you can still use the id, which will be ignored pre Oreo:

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    int importance = NotificationManager.IMPORTANCE_LOW;
    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});
    notificationManager.createNotificationChannel(notificationChannel);
}

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID);

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify((int)(System.currentTimeMillis()/1000), mBuilder.build());