How do you make the popup menu of a JComboBox visible?

Question

How do you make the popup menu of an editable JComboBox visible? When I enter any text in the JComboBox's textfield it should display its popup list items. Here is my code. I have added a KeyListener in which I invoke showPopup() and setPopupVisible(true). But it does nothing.

import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JComboBox;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Test extends JFrame {

private JPanel contentPane;
private JComboBox comboBox;
private JTextField textField;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Test frame = new Test();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the frame.
 */
public Test() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);
    
    comboBox = new JComboBox(new Object[] {"Ester", "Jordi", "Jordina", "Jorge", "Sergi"});
    comboBox.addKeyListener(new KeyAdapter() {
        @Override
        public void keyPressed(KeyEvent arg0) {
            comboBox.showPopup();
            comboBox.setPopupVisible(true);
        }
    });
    comboBox.setEditable(true);
    comboBox.setBounds(10, 11, 414, 20);
    contentPane.add(comboBox);
}
}

Basically, your KeyListener should be attached to the physical editor contained in the comboBox, but, I'd discourage the use of KeyListener in favour of DocumentListener or DocumentFilter instead, depending on your intentions — MadProgrammer, Jan 29 '17 at 07:27
Null layouts are generally a bad idea, which introduce a high level of issues and continued maintenance — MadProgrammer, Jan 29 '17 at 07:28

score 1 · Accepted Answer · edited May 23 '17 at 10:29

I did some work and somehow made it work. But this is not the recommended way. Please add following code after

comboBox = new JComboBox(new Object[] {"Ester", "Jordi", "Jordina", "Jorge", "Sergi"});

Component[] comps = comboBox.getComponents();
for(Component comp : comps){
    if(comp instanceof CellRendererPane){
        JComboBox co = (JComboBox) ((CellRendererPane)comp).getParent();
        co.getEditor().getEditorComponent().addKeyListener(new KeyAdapter()      {
            @Override
            public void keyPressed(KeyEvent arg0) {
                comboBox.showPopup();
                comboBox.setPopupVisible(true);
            }
        });
    }
}

This is working fine.But it's better to use decorator and have new components, also have a look into following article,

JComboBox autocomplete

`JComboBox#getEditor#getEditorComponent`? – MadProgrammer Jan 29 '17 at 20:50 — MadProgrammer, Jan 29 '17 at 20:50

How do you make the popup menu of a JComboBox visible?

1 Answers1