Android notification is not showing

You were missing the small icon. I did the same mistake and the above step resolved it.

As per the official documentation: A Notification object must contain the following:

1. A small icon, set by setSmallIcon()

2. A title, set by setContentTitle()

3. Detail text, set by setContentText()

4. On Android 8.0 (API level 26) and higher, a valid notification channel ID, set by setChannelId() or provided in the NotificationCompat.Builder constructor when creating a channel.

See http://developer.android.com/guide/topics/ui/notifiers/notifications.html

The code won't work without an icon. So, add the setSmallIcon call to the builder chain like this for it to work:

.setSmallIcon(R.drawable.icon)

---

Android Oreo (8.0) and above

Android 8 introduced a new requirement of setting the channelId property by using a NotificationChannel.

NotificationManager mNotificationManager;

NotificationCompat.Builder mBuilder =
    new NotificationCompat.Builder(mContext.getApplicationContext(), "notify_001");
Intent ii = new Intent(mContext.getApplicationContext(), RootActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(mContext, 0, ii, 0);

NotificationCompat.BigTextStyle bigText = new NotificationCompat.BigTextStyle();
bigText.bigText(verseurl);
bigText.setBigContentTitle("Today's Bible Verse");
bigText.setSummaryText("Text in detail");

mBuilder.setContentIntent(pendingIntent);
mBuilder.setSmallIcon(R.mipmap.ic_launcher_round);
mBuilder.setContentTitle("Your Title");
mBuilder.setContentText("Your text");
mBuilder.setPriority(Notification.PRIORITY_MAX);
mBuilder.setStyle(bigText);

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

// === Removed some obsoletes
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
{
    String channelId = "Your_channel_id";
    NotificationChannel channel = new NotificationChannel(
                                        channelId,
                                        "Channel human readable title",
                                        NotificationManager.IMPORTANCE_HIGH);
   mNotificationManager.createNotificationChannel(channel);
  mBuilder.setChannelId(channelId);
}

mNotificationManager.notify(0, mBuilder.build());

Actually the answer by ƒernando Valle doesn't seem to be correct. Then again, your question is overly vague because you fail to mention what is wrong or isn't working.

Looking at your code I am assuming the Notification simply isn't showing.

Your notification is not showing, because you didn't provide an icon. Even though the SDK documentation doesn't mention it being required, it is in fact very much so and your Notification will not show without one.

addAction is only available since 4.1. Prior to that you would use the PendingIntent to launch an Activity. You seem to specify a PendingIntent, so your problem lies elsewhere. Logically, one must conclude it's the missing icon.

This tripped me up today, but I realized it was because on Android 9.0 (Pie), Do Not Disturb by default also hides all notifications, rather than just silencing them like in Android 8.1 (Oreo) and before. This doesn't apply to notifications.

I like having DND on for my development device, so going into the DND settings and changing the setting to simply silence the notifications (but not hide them) fixed it for me.