How to use Android&IOS OS built-in voice input function in Flutter App

Question

I want to use Android OS built-in voice Function in the keyboard in my app.

enter image description here

I want using this function like when I navigate next page, show up the keyboard like above image.

I am using dart language in Flutter but I will not use google STT platform.

So, How do I use built-in voice input function in my keyboard automatically show up when I navigate other page.

And I want to know key code of OS built-in voice Function enter image description here

I tried these,

1. Use google STT, but pricing problem...
2. flutter_speech_to_text package, change the package code but still has short term and accuracy..
3. Use some other STT, but they don't support Korean