Multiple notifications to the same activity
If the PendingIntent has the same operation, action, data, categories, components, and flags it will be replaced.
Depending on the situation i usually solve this by providing a unique request code either as static values (0,1,2) or the row id of the data I'm receiving from the DB.
PendingIntent.getActivity(context, MY_UNIQUE_VALUE , notificationIntent, PendingIntent.FLAG_ONE_SHOT);Then I use the same unique value for notify() as
mNotificationManager.notify(MY_UNIQUE_VALUE, notification);