Double click event on JList element

Question

I've got a problem, and I can't find an answer by myself. I'm making a simple chat in java, and I populated a JList with names. When a name is double-clicked, that name needs to be passed as an argument to another frame (as a recipient name). But, double click does not work

I've got a main class InstantMessageFrame, in which a JList named friends is initialized and filled with an array of strings.

private JList<String> friends;
String names[] = { "Ana", "Banana", "Cikla", "Doris", "Ema", "Mirna","Matea","Veronika","Vera","Marta","Mirta","Davor","Marko","Matko","Kloki" };
JList<String> friends = new JList<String>(names);

Also,I added a listener to my JList

DisplayMessageDialog dmd = new DisplayMessageDialog();
friends.addMouseListener(dmd);

This is my DisplayMessageDialog class which checks if there was a double click. If there is a double click, a new Frame should appear. None of the lines in the first "if" statement executes (one with the e.getClickCount())

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class DisplayMessageDialog extends MouseAdapter
{
    public void mouseClicked(MouseEvent e)
    {
        JList theList = (JList) e.getSource();
        if (e.getClickCount() == 2) 
        {
            int index = theList.locationToIndex(e.getPoint());
            if (index >= 0) 
            {
                Object o = theList.getModel().getElementAt(index);
                InstantMessageDialog imd = new InstantMessageDialog(null, o.toString());
                imd.setVisible(true);
            System.out.println("Double-clicked on: " + o.toString());
            }
        }
    }
}

This is how it should look like:

https://i.stack.imgur.com/Bex5U.png

And when double clicked,a new frame should appear (in code "InstantMessageDialog" object)

https://i.stack.imgur.com/yjvW6.png

And it should look like this.

Answer 1

So working off your out-of-context code snippets, this example seems to work just fine, so I can only surmise that your problem is else where in your code that you're not showing us...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JList<String> friends;

        public TestPane() {
            String names[] = {"Ana", "Banana", "Cikla", "Doris", "Ema", "Mirna", "Matea", "Veronika", "Vera", "Marta", "Mirta", "Davor", "Marko", "Matko", "Kloki"};
            JList<String> friends = new JList<String>(names);

            setLayout(new BorderLayout());
            add(new JScrollPane(friends));

            DisplayMessageDialog dmd = new DisplayMessageDialog();
            friends.addMouseListener(dmd);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.dispose();
        }

    }

    public class DisplayMessageDialog extends MouseAdapter {

        public void mouseClicked(MouseEvent e) {
            JList theList = (JList) e.getSource();
            //              if (SwingUtilities.isLeftMouseButton(e) && e.getClickCount() == 2) {
            if (e.getClickCount() == 2) {
                int index = theList.locationToIndex(e.getPoint());
                if (index >= 0) {
                    Object o = theList.getModel().getElementAt(index);
                            //InstantMessageDialog imd = new InstantMessageDialog(null, o.toString());
                    //imd.setVisible(true);
                    JOptionPane.showMessageDialog(theList, "Double-clicked on: " + o.toString());
                    System.out.println("Double-clicked on: " + o.toString());
                }
            }
        }
    }
}

I might add though, you "double click" check probably should be something more like...

if (SwingUtilities.isLeftMouseButton(e) && e.getClickCount() == 2) {

Assuming your really only want to respond to left mouse clicks

Answer 2

When a name is double-clicked...

When designing a GUI it is always a good idea to provide support for the mouse and keyboard.

Check out List Action. It adds Action support to a JList. All you need to do is provide the Action. Then the Action can be invoked by:

1. double clicking, or
2. using the Enter key.

The most basic example of using the ListAction would be:

String[] data = { "zero", "one", "two", "three", "four", "five" };
JList list = new JList( data );

Action displayAction = new AbstractAction()
{
    public void actionPerformed(ActionEvent e)
    {
        JList list = (JList)e.getSource();
        System.out.println(list.getSelectedValue());
    }
};

ListAction la = new ListAction(list, displayAction);