Stop JcomboBox dropdown

Question

Hi everyone,
I have a requirement to not allow the dropdown list of JComboBox to pop up in certain situations. I could disable the combo box, but that is not the preferred option. I tried to over write JComboBox.firePopupMenuWillBecomeVisible(). The problem with that is: the drop down list (which is a pop up) is already set to visible at this time.
Any suggestion?
Thanks,
Genseng

Answer 1

this might be one way
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.plaf.basic.BasicComboBoxUI;
import javax.swing.plaf.basic.BasicComboPopup;
class Testing extends JFrame
  JComboBox cbo = new JComboBox(new String[]{"London","Madrid","New York","Rome","Sydney","Washington"});
  JRadioButton rb = new JRadioButton("No Popup");
  public Testing()
    setLocation(400,300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    cbo.setUI(new MyUI());
    JPanel jp = new JPanel();
    jp.add(rb);
    jp.add(cbo);
    getContentPane().add(jp);
    pack();
    rb.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent ae){
        if(rb.isSelected()) cbo.setUI(new MyUI_NoPopup());
        else cbo.setUI(new MyUI());}});
  class MyUI extends BasicComboBoxUI
    protected javax.swing.plaf.basic.ComboPopup createPopup()
      return super.createPopup();
  class MyUI_NoPopup extends BasicComboBoxUI
    protected javax.swing.plaf.basic.ComboPopup createPopup()
      BasicComboPopup popup = (BasicComboPopup)super.createPopup();
      popup.setPreferredSize(new Dimension(0,0));
      return popup;
  public static void main(String args[]){new Testing().setVisible(true);}
}