I've implemented a system in Flutter in which I can choose my language from a menu. The program starts by default in English but when I try to set it to Spanish or French it doesn't work.

I know that in the readme.md says that to make it work, more configuration is needed. The question is what do I need to do to make it work in other languages.

_speech.listen( locale: widget._language ).then((result) => setState(() {
print("Listening ${result}");
this.setState(() {
transcription = result;
});
}));