Communicate between two android apps : I am developing a unity android app and an android studio app. I want to open and close them using each other and to pass messages between them. How can I achieve this? 
1. How to create a intent of the unity app in android studio?
2. How to invoke a method of unity app inside android studio app?
3. How to invoke a method of android studio app inside unity app?

I am completely new to android development. Even though there are similar questions, couldn't find a solution that worked for me. Thank you.