If acceptable, please remove this first paragraph. I hope this is good enough. I don't know what else you want/need. I explained my end goal. I specified my IDE and language. I specified my platform. I explained what I have tried. Then, I very succinctly asked my one specific question.
My "end goal" is to receive audio on my Samsung Galaxy s10e phone and send it immediately to my Phonak hearing aids through Bluetooth. First, I searched "Play Store" to find an app. Every app I tried had a delay that was too long (I will be hearing both live voice and Bluetooth input, so bluetooth can't lag by much). So, I decided to write my own phone app. I have no need to record.
I searched the internet and every web site I encountered suggested a different package. I searched Samsung's site to see if they have a defined interface between Java and their phone. I tried looking at packages' documentation. I have been UNABLE to determine which package(s) I should use.
I will be using "Android Studio" to write a Phone App in Java. What package(s) do I need to Setup/Control the phone's microphone?