ActionListener on JComboBox fires subsequently on next all Comboxes

[Sharad Kharya]

Hello,
I am facing a problem with JComboBox ActionListener. I have 3 comboBox and the logic which I am expecting is -
User select Item from 1st combobox, then only 2nd comboBox will be populated.
then user selects 2nd combobox, then 3rd comboBox will gets populated.
...
and so on.

I have made only 3 combobox here for this post. in an actual scenario I have around 8-10 combobox'x each having nearly 10 items.


The problem I am facing here is very tedious. All the listeners in all combobox's fired.
I tried removing and then re-adding action listener, but that gives me compilation issue.
1st issue - Cannot refer to a non-final variable listener inside an inner class defined in a different method
to correct this, if I make ActionListener definition as final, then another compilation issue comes - The local variable listener may not have been initialized.

Please help me in resolving this.
Code snippet -

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Arrays;
import java.util.HashMap;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ComboBoxListener {
	
	HashMap hmMappingOfNextField = new HashMap();
	HashMap hm1and2and3mapping = new HashMap();
	
	
	public static void main(String[] args) {
		ComboBoxListener obj = new ComboBoxListener();
		obj.addComboBox();
	}
	
	public void addComboBox()
	{
		String[] cb1Arr = {"A", "B", "C"};
		
		JFrame frame = new JFrame("Check Combo box events");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		final JComboBox cb1 = new JComboBox(cb1Arr);		
		cb1.setName("cb1");
		final JComboBox cb2 = new JComboBox();		
		cb2.setName("cb2");
		final JComboBox cb3 = new JComboBox();
		cb3.setName("cb3");
		
		JPanel panel = new JPanel();
		panel.add(cb1);
		panel.add(cb2);
		panel.add(cb3);
		
		
		//HM to hold next update field.
		hmMappingOfNextField.put("cb1", cb2);
		hmMappingOfNextField.put("cb2", cb3);
		hmMappingOfNextField.put("cb3", null);
		
		hm1and2and3mapping.put("A", new String[]{"A.A", "A.B", "A.C"});
		hm1and2and3mapping.put("B", new String[]{"B.A", "B.B", "B.C"});
		hm1and2and3mapping.put("C", new String[]{"C.A", "C.B", "C.C"});
		
		hm1and2and3mapping.put("A.A", new String[]{"A.A.A.A", "A.A.A.B", "A.A.A.C"});
		hm1and2and3mapping.put("A.B", new String[]{"A.A.B.A", "A.A.B.B", "A.A.B.C"});
		hm1and2and3mapping.put("A.C", new String[]{"A.A.C.A", "A.A.C.B", "A.A.C.C"});
		
		hm1and2and3mapping.put("B.A", new String[]{"B.B.A.B", "B.B.A.B", "B.B.A.C"});
		hm1and2and3mapping.put("B.B", new String[]{"B.B.B.A", "B.B.B.B", "B.B.B.C"});
		hm1and2and3mapping.put("B.C", new String[]{"B.B.C.A", "B.B.C.B", "B.B.C.C"});
		
		hm1and2and3mapping.put("C.A", new String[]{"C.C.A.A", "C.C.A.B", "C.C.A.C"});
		hm1and2and3mapping.put("C.B", new String[]{"C.C.B.A", "C.C.B.B", "C.C.B.C"});
		hm1and2and3mapping.put("C.C", new String[]{"C.C.C.A", "C.C.C.B", "C.C.C.C"});
		
		
		final ActionListener listener = new ActionListener() {			
			@Override
			public void actionPerformed(ActionEvent event) 
			{
				JComboBox cb = (JComboBox)event.getSource();
				
				//cb.removeActionListener(listener);
				
				String cbNameOnWhichEventIsFired = cb.getName();
				System.out.println("cbNameOnWhichEventIsFired===="+cbNameOnWhichEventIsFired);
				
				Object cbObjToBeUpdated = hmMappingOfNextField.get(cbNameOnWhichEventIsFired);
				JComboBox cbToBeUpdated = (JComboBox)cbObjToBeUpdated;
				
				String cbSelectedItem= (String)cb.getSelectedItem();
				if( cbSelectedItem != null)
				{
					String[] mapppingArr = (String[])hm1and2and3mapping.get(cbSelectedItem);
					System.out.println(Arrays.asList(mapppingArr));
					
					cbToBeUpdated.removeAllItems();
					for(int i=0; i<mapppingArr.length; i++)
					{
						cbToBeUpdated.addItem(mapppingArr[i]);
					}
				}
				
				//cb.addActionListener(listener);
			}
		};
		
		//System.out.println("=========================");
		cb1.addActionListener(listener);
		cb2.addActionListener(listener);
		//cb3.addActionListener(listener);
		
		frame.add(panel, BorderLayout.NORTH);
		frame.setSize(300, 200);
		frame.setVisible(true);
	}
}

Thanks In Advance,
Sharad
>

[m Korbel]

- all data for JComponents are stored in Model

- put data to the DefaultComboBoxModel,

- from ItemListener (suitable, better listener for JComboBox) or ActionListener to switch betweens model

- code example by Rob or Darryl from old.sun.forums57 (little bit modified)

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class ComboBoxTwo {

    private static final long serialVersionUID = 1L;
    private JFrame frame = new JFrame();
    private JComboBox mainComboBox;
    private JComboBox subComboBox;
    private String[] items = {"Select Item", "Color", "Shape", "Fruit"};
    private Hashtable<Object, Object> subItems = new Hashtable<Object, Object>();
    private String[] subItems1 = {"Select Color", "Red", "Blue", "Green"};
    private String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"};
    private String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"};

    public ComboBoxTwo() {
        mainComboBox = new JComboBox(items);
        mainComboBox.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                String item = (String) mainComboBox.getSelectedItem();
                Object o = subItems.get(item);
                if (o == null) {
                    subComboBox.setModel(new DefaultComboBoxModel());
                } else {
                    subComboBox.setModel(new DefaultComboBoxModel((String[]) o));
                }
            }
        });
        mainComboBox.addItemListener(new ItemListener() {

            @Override
            public void itemStateChanged(ItemEvent e) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    if (mainComboBox.getSelectedIndex() != 0) {
                        FirstDialog firstDialog = new FirstDialog(frame,
                                mainComboBox.getSelectedItem().toString(),
                                "Please wait,      Searching for ..... ");
                    }
                }
            }
        });
        mainComboBox.setPrototypeDisplayValue("XXXXXXXXXXXXXXXX");
        //prevent action events from being fired when the up/down arrow keys are used
        mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
        subComboBox = new JComboBox();//  Create sub combo box with multiple models
        subComboBox.setPrototypeDisplayValue("XXXXXXXXXXXXXXXX"); // JDK1.4
        subItems.put(items[1], subItems1);
        subItems.put(items[2], subItems2);
        subItems.put(items[3], subItems3);
        frame.add(mainComboBox, BorderLayout.WEST);
        frame.add(subComboBox, BorderLayout.EAST);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocation(150, 150);
        frame.setVisible(true);
    }

    private class FirstDialog extends JDialog {

        private static final long serialVersionUID = 1L;

        FirstDialog(final Frame parent, String winTitle, String msgString) {
            super(parent, winTitle);
            setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
            JLabel myLabel = new JLabel(msgString);
            JButton bNext = new JButton("Stop Processes");
            add(myLabel, BorderLayout.CENTER);
            add(bNext, BorderLayout.SOUTH);
            bNext.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent evt) {
                    setVisible(false);
                }
            });
            javax.swing.Timer t = new javax.swing.Timer(1500, new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    setVisible(false);
                }
            });
            t.setRepeats(false);
            t.start();
            setLocationRelativeTo(parent);
            setSize(new Dimension(400, 100));
            setVisible(true);
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                ComboBoxTwo comboBoxTwo = new ComboBoxTwo();
            }
        });
    }
}

[Sharad Kharya]

Thanks. This logic works for me.
I am just posting the code differences I made to make it work w.r.t the original example.

old code snippet

......
cbToBeUpdated.removeAllItems();
for(int i=0; i<mapppingArr.length; i++)
{
     cbToBeUpdated.addItem(mapppingArr[i]);
}
.....

Changed code snippet

.....
cbToBeUpdated.setModel(new DefaultComboBoxModel(mapppingArr));
.....

>