I want to trigger an additional event in an android app when the default speech recognition button is touched on the android soft-keyboard. Is there any method catching this event, or what is the code for the speech recognition button to modify the keyboard.xml directly? Any solution would be appreciated, thanks.
None. Software keyboards don't generate keyboard events. They send text via InputConnection.commiteTexzt. For a button that causes no text like speech, it would internally launch a speech recognition app, either the default one or one of their choosing.
If you're looking to implement a basic keyboard yourself, just have the key launch an intent with action RecognizerIntent.ACTION_RECOGNIZE_SPEECH. If you want something fancier you pretty much have to bind with a specific voice recognition library directly.