Just a suggestion #1
Description
I really don't know anything about code. What I do know is that this is the only game in town in terms of a free/opensource solution for Android TTS. There's also something called espeak, but it's F-Droid repository hasn't been updated in a couple of years and it crashes on Android 6.0 (though I found them on Github and it appears that there is a recent fork, so I'm going to download Android Studio and see if I can't get it to build).
It seems like you're trying to build your own client here with this project, but from what I understand espeak already has that covered, you'd just need to rip out the espeak voice tech and replace it with the AndroidMaryTTS tech? Sorry, I'm a novice with this stuff, but I'd hate to let you reinvent the wheel when a project already exists that might save you some time.
Great work so far, I look forward to using the project once it's implemented!
Here's a link to the fork I was talking about:
https://github.com/espeak-ng/espeak-ng/tree/android