EventListeners

Sources

Summary

When the user types on the keyboard, or uses the mouse, the operating system produces an event. In Java, there are a few basic rules for using these events:

• Any class that wants to respond to events must implement a listener interface.
  • Examples: ActionListener, WindowListener, MouseListener
  • Java.awt.event package has ‘listener adapter’ classes that you may extend instead of writing your own classes
• In order for an object to handle an event, it must register with an add(type)Listener message which is sent to the calling method.
• Then, you must implement an ActionPreformed method. This is called whenever an action is preformed.
  • Example: public void actionPreformed (ActionEvent e) {}

Example:

public class Beeper ... implements ActionListener {
    ...
    //where initialization occurs:
        button.addActionListener(this);
    ...
    public void actionPerformed(ActionEvent e) {
        ...//Make a beep sound...
    }
}