Regular apps cannot do it. You can implement an accessibility app however it will only work if the user will enable your app. Search for accessibility service.
Thank you Erel. Read through the accessibility service and notification listener, but still don't know how to reach what I need..
In the example of the accessibility service thread it only teaches us to automatically send a whatsapp message but not to read one. And with the notification listener it only captures the received msg (i.e. those provokes notification) but no those which the user sends out..
Any example code which can help me out?