Event listener in Java without app having focus? (Global keypress detection)

Question

I've been searching for a while and everybody seems to think this is not possible using just Java, so I'll give SO a shot ;)

Is there any way to have my Java application listen for events (key events in particular) while another unrelated application has window focus? In my situation, I'm looking to detect when the user has pressed the 'Pause' key on the keyboard even though my Java application does not have focus.

I've heard some people mention that the only way is to write some C code and use JNI. Just curious if anybody knew of a way to avoid that? Or, if not, at least a really nice tutorial on the c/JNI stuff?

Thanks

Answer 1

It's my understanding that this can't be done. At a fundamental level, the JVM only generates events for O/S events it receives, and it only receives O/S input events when it has focus.

I am sure you could use JNI to trigger the O/S to generate events for all input, but that would be very O/S dependent.

Answer 2

I'm not aware of any way to get around that either. I did find this link on Java's forums with a good example of how to setup the JNI stuff and make a global keyboard handler (too much to add here). It's a little dated (2005), but the example looks thorough enough to get you started.