Java Reference
In-Depth Information
import javax.swing.*;
import java.awt.*;
public class JRadioButtonDemo extends JFrame
{
private JRadioButton small, medium, large;
private JButton button;
public JRadioButtonDemo(String title)
{
super(title);
this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
Container contentPane = this.getContentPane();
ButtonGroup group = new ButtonGroup();
small = new JRadioButton(“small”);
medium = new JRadioButton(“medium”);
large = new JRadioButton(“large”);
//add the radio buttons to the same group
group.add(small);
group.add(medium);
group.add(large);
button = new JButton(“Click here.”);
button.setBounds(100,50,100, 50);
JPanel center = new JPanel();
center.setLayout(null);
center.add(button);
contentPane.add(center, BorderLayout.CENTER);
//add the radio buttons to the frame
JPanel north = new JPanel();
north.add(small);
north.add(medium);
north.add(large);
contentPane.add(north, BorderLayout.NORTH);
//register the event listener
SwingChangeSize listener = new SwingChangeSize(button);
small.addItemListener(listener);
medium.addItemListener(listener);
large.addItemListener(listener);
}
public static void main(String [] args)
{
JFrame f = new JRadioButtonDemo(“JRadioButtonDemo”);
f.setSize(300,200);
f.setVisible(true);
}
}
In the SwingChangeSize class, the getItem() method of the ItemEvent object
returns a reference to the radio button that was clicked. The getText() method
is used to obtain the label of the radio button, and the component is resized
accordingly, as demonstrated in Figure 13.7.
