problem with JCombobox

[djay djay]

I have a combobox on panel. Also I have a Jbutton 'search'with function key F2
on a dilaog. The panel where combobox is added is added on dialog
I am filling some data into the combobox.
When I select any item from combobox and click on 'search' button
then eveything works fine.
But if instead of clicking on button using mouse if I pressed F2 key
on keyboard i am getting following error message

java.lang.NullPointerException
at javax.swing.JComboBox$DefaultKeySelectionManager.selectionForKey(JComboBox.java:1207)
at javax.swing.JComboBox.selectWithKeyChar(JComboBox.java:1003)
at javax.swing.plaf.basic.BasicComboBoxUI$KeyHandler.keyPressed(BasicComboBoxUI.java:425)
at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:204)
at java.awt.Component.processKeyEvent(Component.java:3761)
at javax.swing.JComponent.processKeyEvent(JComponent.java:2073)
at java.awt.Component.processEvent(Component.java:3637)
at java.awt.Container.processEvent(Container.java:1202)
at java.awt.Component.dispatchEventImpl(Component.java:2678)
at java.awt.Container.dispatchEventImpl(Container.java:1251)
at java.awt.Component.dispatchEvent(Component.java:2581)
at java.awt.LightweightDispatcher.processKeyEvent(Container.java:2200)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2180)
at java.awt.Container.dispatchEventImpl(Container.java:1238)
at java.awt.Window.dispatchEventImpl(Window.java:964)
at java.awt.Component.dispatchEvent(Component.java:2581)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:434)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:141)
at java.awt.Dialog.show(Dialog.java:394)

Any idea to resolve this problem?

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class KeyBinding
{
    JComboBox comboBox;
    JLabel label;
 
    public KeyBinding()
    {
        String[] items = { "item 1", "item 2", "item 3", "item 4" };
        comboBox = new JComboBox(items);
        comboBox.getInputMap().put(KeyStroke.getKeyStroke("F2"), "SEARCH");
        comboBox.getActionMap().put("SEARCH", search);
        JButton button = new JButton();
        button.setAction(search);
        JPanel north = new JPanel();
        north.add(comboBox);
        north.add(button);
        label = new JLabel(" ", JLabel.CENTER);
        JPanel south = new JPanel();
        south.add(label);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(north, "North");
        f.getContentPane().add(south, "South");
        f.setSize(300,100);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    public static void main(String[] args)
    {
        new KeyBinding();
    }
 
    private Action search = new AbstractAction("search")
    {
        public void actionPerformed(ActionEvent e)
        {
            String item = (String)comboBox.getSelectedItem();
            label.setText(item);
        }
    };
}