Hi
I regularly import exported keys into multibit. You just have to export the file on Android, copy it to your PC and then use the import feature from multibit. There is a password field where you enter your password and afterwards click on unlock. Then the import should be no problem.
Thanks. I wouldn't have tried again if not for you comment. The client on android saved the file without an extension. Multibit doesn't interpret the file correctly unless the extension is "*.key". Renamed the file, now it works.
I've been exclusive on linux for the past decade, so I'm used to other heuristics determining the file type regardless of extension.