JList where mouse click acts like ctrl-mouse click

Question

I'd like to create a JList where I can select multiple items as if the control key were down, but without having the control key down. I thought that perhaps I could do this by extending JList and overriding its processMouseEvent method, setting the MouseEvent object to think that control is pressed and then calling the super method like so, but it doesn't work (I still need to press the control key to get my desired effect):
import java.awt.Component;
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;
import javax.swing.*;
public class Ctrl_Down_JList {
  private static void createAndShowUI() {
    String[] items = {"Sun", "Mon", "Tues", "Wed", "Thurs", "Fri", "Sat"};
    JList myJList = new JList(items) {
      @Override
      protected void processMouseEvent(MouseEvent e) {
        // change the modifiers to believe that control key is down
        int modifiers = e.getModifiers() | InputEvent.CTRL_DOWN_MASK;
        // can I use this anywhere?  I don't see how to change the
        // modifiersEx of the MouseEvent
        int modifiersEx = e.getModifiersEx() | InputEvent.CTRL_DOWN_MASK;
        MouseEvent myME = new MouseEvent(
            (Component) e.getSource(),
            e.getID(),
            e.getWhen(),
            modifiers, // my changed modifier
            e.getX(),
            e.getY(),
            e.getXOnScreen(),
            e.getYOnScreen(),
            e.getClickCount(),
            e.isPopupTrigger(),
            e.getButton());
        super.processMouseEvent(myME);
    JFrame frame = new JFrame("Ctrl_Down_JList");
    frame.getContentPane().add(new JScrollPane(myJList));
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
      public void run() {
        createAndShowUI();
}Any ideas would be much appreciated!

Answer 1

Any ideas would be much appreciated!Here is a hack, idea is same as yours, but using Robot:
public static void createAndShowUI2() {
     String[] items = { "Sun", "Mon", "Tues", "Wed", "Thurs", "Fri", "Sat" };
     final JList myJList = new JList(items);
     myJList.addMouseListener(new MouseAdapter() {
          Robot robot;
               try {
                    robot = new Robot();
               } catch (AWTException ex) {
                    ex.printStackTrace();
          @Override
          public void mouseEntered(MouseEvent e) {
               if (robot != null)
                    robot.keyPress(KeyEvent.VK_CONTROL);
          @Override
          public void mouseExited(MouseEvent e) {
               if (robot != null)
                    robot.keyRelease(KeyEvent.VK_CONTROL);
     JFrame frame = new JFrame("Ctrl_Down_JList");
     frame.getContentPane().add(new JScrollPane(myJList));
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     frame.pack();
     frame.setLocationRelativeTo(null);
     frame.setVisible(true);
}It does work, but there has to be some cleaner way of doing this, perhaps using SelectionModel but I don't know about it.
Thanks!
Edit: I found that if Control key is pressed manually, then this hack obviously, to handle this, it has to made dirtier:
myJList.addMouseListener(new MouseAdapter() {
     Robot robot;
          try {
               robot = new Robot();
          } catch (AWTException ex) {
               ex.printStackTrace();
     Timer timer = new Timer(20, new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent e) {
               if (robot != null)
                    robot.keyPress(KeyEvent.VK_CONTROL);
        @Override
     public void mouseEntered(MouseEvent e) {
          if (robot != null) {
               robot.keyPress(KeyEvent.VK_CONTROL);
               timer.start();
        @Override
     public void mouseExited(MouseEvent e) {
          if (robot != null) {
               robot.keyRelease(KeyEvent.VK_CONTROL);
               timer.stop();
});Edited by: T.B.M on Mar 13, 2010 10:06 PM