Event and Event Handling
An event is a signal, like mouse click, key press, window resize etc, received by a program from some source like operating system as user has done some kind of action (key press, mouse click) or something else has happened.
Delegation model:
In Java, delegation model is used to handle events.
- A component (source) registers itself with a source to receive a signal or event notification.
- As source receives signal, it sends event notification to the registered listener.
- The listener receives event notification, processes the event and returns.
A listener object may be defined by:
- Implementing a listener interface
- Using object of listener interface
For example,
Class abc implements ActionListener{
//a class abc implementing to listener interface,
}
button.addActionListener(this);
//button registering to the event handler class, here object of class abc itself,
Public void actionPerformed(ActionEvent ae){
//event handler class implements the method in the listener interface to handle an event.
}