Using listeners to respond to application changes
A BlackBerry® Java® Application can register change listeners on the email and organizer data stores and in the phone application. The listeners allow the BlackBerry Java Application to take immediate action when the BlackBerry device user performs a local event. You can use the email and organizer data listeners to notify a BlackBerry Java Application when new entries arrive or when the BlackBerry device user makes changes such as additions, deletions, or updates, to the existing data. You can use phone listeners to listen for phone call actions, such as the initiation of new calls or calls ending.