HANDLING EXCEPTIONS AND EVENTS - Java Programming: From Problem Analysis to Program Design - page 761

Chapter 6 discussed in detail how to handle action events. Recall that to handle an action
event, we do the following:
1. Create a class that implements the interface ActionListener . For
example, in Chapter 6, for the JButton calculateB , we created the
class CalculateButtonHandler .
2. Provide the definition of the method actionPerformed within the class
that you created in Step 1. The method actionPerformed contains the
code that the program executes when the specific event is generated. For
example, in Chapter 6, when you click the JButton calculateB ,the
program should calculate and display the area and perimeter of the rectangle.
3. Create and instantiate an object of the class created in Step 1. For
example, in Chapter 6, for the JButton calculateB , we created the
object cbHandler .
4. Register the event handler created in Step 3 with the object that generates
an action event using the method addActionListener . For example, in
Chapter 6, for the JButton calculateB , the following statement registers
the object cbHandler to listen for and register the action event:

calculateB.addActionListener(cbHandler);
Just as you create objects of the class that extends the interface ActionListener to
handle action events, to handle window events you first create a class that implements the
interface WindowListener and then create and register objects of that class. You take
similar steps to handle mouse events.
In Chapter 6, to terminate the program when the close window button is clicked, we
used the method setDefaultCloseOperation with the predefined named constant
EXIT_ON_CLOSE . If you want to provide your own code to terminate the program when
the window is closed, or if you want the program to take a different action when the
window closes, then you use the interface WindowListener . That is, first you create
a class that implements the interface WindowListener , provide the appropriate
definition of the method windowClosed , create an appropriate object of that class, and
then register the object created with the program.
Let's look at the definition of the interface WindowListener :
public interface WindowListener
{

1
1

void windowActivated(WindowEvent e);
//This method executes when a window is activated.
void windowClosed(WindowEvent e);
//This method executes when a window is closed.
void windowClosing(WindowEvent e);
//This method executes when a window is closing,
//just before a window is closed.
void windowDeactivated(WindowEvent e);
//This method executes when a window is deactivated.