How to react to speech in android?

Question

Java

Hello. How to respond to speech in android? Any language, any method will do, the main thing is to be offline.
We need a voice recorder that records only if there is human speech around, I decided to implement it myself. Experience in android - zero, I will study.
Therefore, I’d better ask right away, I googled Intent ACTION_RECOGNIZE_SPEECH , which calls OnActivityResult with speech recognition, but as far as I understand, this requires an Internet connection.
How to make offline speech recognition as much as possible regardless of android versions?
It is painfully reluctant to train an audio classifier in TF and figure out how to port everything to a mobile phone, just to recognize the fact of the balabolny around. Can it be easier?
Thanks