Event Handling

An event generally occurs when some thing happened on a Graphical user interface component.

For Example

User can click the button, then mouse click event happened on the button.

User can select a check box, then selection event happened on the check box.

Events may also occurs that are not directly caused by the interactions with user interface.

For Example

An Event may be generated when counter exceeds a value, timer expires etc.,

Event Source

The Graphical component generating the event is called Event source. Whenever an event occurs, the Event Source sends an event object, which contains the information about the event to the listeners.

Event Listener

A listener is an object that is notified when an event occurs. The event object gets processed by an event listener

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