The Graphical User Interfaces - SCJD Exam with J2SE 5 - page 249

The first point can be worth consideration, but if you are using the MVC pattern, you
might prefer to have the Controller handle the user events. Alternatively, a simple anonymous
class can call a method in the Controller class, making the Controller class less dependent on
the GUI architecture.
The last point can be both good and bad as well—you might not want the code handling
the event with the code that is configuring the View. It might make more sense to keep event-
handling code separate.
If you do decide to have a separate class or method handling events, you might want to
consider using the setActionCommand method to set a string by which your component can be
easily identified. The string you set can then be retrieved from the ActionEvent handed to the
actionPerformed method. This is demonstrated in Listing 8-6 in the next section.
The JRadioButton Component
Radio buttons are small buttons that are logically grouped together, but only one of the group
can be active at any given time. This is similar to the way a radio with buttons for several pre-
set stations should only have one button pressed at any given time—you can only listen to one
station at a time.
A simple constructor for a JRadioButton could be
JRadioButton serverButton = new JRadioButton("Server");
Other constructors allow for an icon to be used instead of or as well as the text, setting the
initial state of the radio button, and setting an Action for the radio button.
As with the JButton , an ActionListener can be added to each JRadioButton . You might
use this if you needed to enable or disable fields dependent on which button a user clicked.
However, it is not always necessary to have an ActionListener —if you don't care about which
button is clicked until after the user performs some other action, then you can use the
isSelected method to check the user's choice.
For JRadioButton s to be effective, several of them should be logically grouped together, so
that only one of the logical group can be selected at any given time. You do this by creating a
ButtonGroup , and adding the radio buttons to it:
ButtonGroup applicationMode = new ButtonGroup();
applicationMode.add(serverButton);
A complete example of JButton s and JRadioButton s is demonstrated in Listing 8-6, and
the window it would create is shown in Figure 8-17.
Listing 8-6. Demonstration of JButton and JRadioButton Components
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyFrame extends JFrame {
private static final String EXIT_COMMAND = "EXIT";
private static final String CLIENT_COMMAND = "CLIENT";
private static final String SERVER_COMMAND = "SERVER";