Listening to notifications from phone or messaging app

[khatauli]

I am developing a custom launcher, and to display the badges on the app icons, I am using NotificationListenerService to know when a new notification arrives in the system for any app. It is working fine, but for the essential apps such as phone, messages, whatsapp etc, I am not able to capture any notification when somebody leaves a message or calls.

I wonder if these essential apps send notifications via a different channel other than NotificationListenerService, or is there some some key property I need to set in the listener so that I can listen to the event in these cases?

Any help will be appreciated.
- Khatauli