Это код для размещения уведомления в трее уведомлений. 100% работает.
NotificationManager notificationManager = (NotificationManager)
getSystemService(NOTIFICATION_SERVICE);
Intent intent = new Intent(this, EndActivity.class);
PendingIntent pIntent = PendingIntent.getActivity(this, (int) System.currentTimeMillis(), intent, 0);
// build notification
// the addAction re-use the same intent to keep the example short
Notification n = new Notification.Builder(this)
.setContentTitle("My message")
.setContentText("Subject")
.setSmallIcon(R.drawable.MyApplogo)
.setContentIntent(pIntent)
.setAutoCancel(true)
.setStyle(new Notification.BigTextStyle().bigText(""+msg.get(3))).build();
// .addAction(R.drawable.line, "", pIntent).build();
n.flags |= Notification.FLAG_AUTO_CANCEL;
notificationManager.notify(0, n);