ActionEvent is not invoked when RETURN key is pressed on the button. Just try to hit return key on the button, you will see actionEvent is not invoked.

This isn't completely clear from the description/synopsis, but I think this 
is another focus bug.  

 xxxxx@xxxxx  1999-04-27

Committing to Merlin.  Dave has agreed to update the docs/spec as 
appropriate.  

 xxxxx@xxxxx  2000-08-22

This is not a focus bug. The KeyEvents are delivered just fine, but the
Button component does not respond to RETURN. This is inconsistent with the
native platform. Both native Motif and Win32 buttons respond to RETURN,
whereas the corresponding AWT native peers do not. This should be corrected.
 xxxxx@xxxxx  2001-07-10

This is not really a bug at all, only an undefined area in the specification.  Space bar is typically the key for invoking a button, not RETURN.  Space bar works fine.
 xxxxx@xxxxx  2001-08-02


Added some doc.  Had reviewed by Roman, approved by CCC.  Fixed for tiger.
 xxxxx@xxxxx  2003-08-22