Android™ How to Program, Second Edition

Event-Handler Invocation

The event-listener type is important in answering the second question: How does the GUI component know to call actionPerformed rather than another method? Every GUI component supports several event types, including mouse events, key events and others. When an event occurs, the event is dispatched only to the event listeners of the appropriate type. Dispatching is simply the process by which the GUI component calls an event-handling method on each of its listeners that are registered for the event type that occurred.

Each event type has one or more corresponding event-listener interfaces. For example, ActionEvents are handled by ActionListeners, MouseEvents by MouseListeners and MouseMotionListeners, and KeyEvents by ...