In an activity can you fix the android keyboard, so that it cannot be closed? I've tried setting the windowSoftInputMode attribute in the AndroidManifest.xml to stateAlwaysVisible, but the keyboard can still be closed. Is what I want possible?
Not really. The keyboard close button is a not really something you can control. I guess you could write your own keyboard and ship that if you really needed to.
Instead of trying to change the OS, why don't you elaborate your question and give some details about Why you need this, maybe we can help you in a more productive manner.