i just want to know b4a has a class or library to make it possible to listem to keyboard?
Well the obvious choice would be to use the Android Accessibility Service, but looking at the documentation for the B4A Accessibility library it looks like only a subset of that functionality has been implemented - & there doesn't appear to be any functionality that would support key logging. If you were going to go down that path you'd have to use JavaObject calls to get it done.
On top of that, Android won't let you just run a background key logging service (for obvious reasons) without jumping through various security hoops, including having the user explicitly set permissions to allow it.
I think (again for obvious reasons) if you want to get any serious assistance from this forum on this you'll probably need to explain in some more detail what you are trying to do & why.
- Colin.