android-phonestatelistener-phone-call-broadcast-receiver-tutorial

https://stackoverflow.com/questions/5990590/how-to-detect-phone-call-broadcast-receiver-in-android


https://gist.github.com/ftvs/e61ccb039f511eb288ee


http://droidcodesnippets.blogspot.com/2012/08/block-all-calls.html

http://www.nikola-breznjak.com/blog/android/make-native-android-app-can-block-phone-calls/

https://www.studytutorial.in/android-phonestatelistener-phone-call-broadcast-receiver-tutorial