Confused after reading bug report

Question

Hello,
I'm working on a desktop application which utilizes the system tray. I have an icon set with a popup menu that is triggered when the user left-clicks on the icon. Originally I was using java.awt.PopupMenu but then came across javax.swing.JPopupMenu which looks a little nicer and has support for icons. For the most part it works great. However I noticed that when the user triggers the popup menu more than once (i.e. the user left-clicks the tray icon twice or more times), a ClassCastException is thrown. After doing a bit of searching, I came across [this bug report|http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6583251] and many others describing the issue I was having.
According to the report, the evaluation is:
Everything is clear
we shouldn't cast mouseEvent.getSource() to Component without checkingUnfortunately this still leaves me a little confused. I mean, it does sort of let me know where the problem is happening (in the MouseListener portion of my Tray Menu where I am trying to detect the popup trigger), but I don't understand if this means that there is a way to prevent this from happening or not.
In other words, I think the bug is coming from this block of code (correct me if I am mistaken):
public void mouseReleased(MouseEvent e) {
          if ( e.isPopupTrigger() ) {
               this.setLocation( e.getX(), e.getY() );
               this.setInvoker( this );
               this.setVisible( true );
     }Where e is apparently being casted to a Component, thus causing the error. Now, why this error occurs when the user clicks twice or more on the icon, I don't really understand. Ultimately, my question is: Is there any other way this can be written to prevent the error?
One solution would be to simply use java.awt.PopupMenu, but I want to make sure there isn't a better solution first as JPopupMenu looks much nicer.. but if I have no other option, I will of course substitute looks for function.
Any clarification would be greatly appreciated.
(Apologies if this is the wrong forum. I was originally going to post this in the Swing forum, but the error actually cites AWT, yet I'm using a Swing component.. so I figured the Java Programming forum would be alright. Well, please feel free to move it if necessary.)

Answer 1

ejp wrote:
The exception stack trace tells you where the exception is being thrown from. It certainly isn't from that code, because there are no class casts of any kind there, let alone casts of e.getSource() to Component.Hi ejp, thank you for the response. My apologies.. I only assumed that e.isPopupTrigger() was throwing the exception because the bug report mentioned mouse events, and the stack trace doesn't specify where the error is within my code (e.g. the line, method, or even which class is throwing the error that I've written, though it does cite other Java classes not written by me). The e.getSource() in actionPerformed() was my next guess because that and the MouseListener are the only two places where I am detecting events. Nevertheless, I still don't believe that I am using casting, so I'm not sure how to fix this.
Here is the stack trace:
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.TrayIcon cannot be cast to java.awt.Component
     at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.eventDispatched(Unknown Source)
     at java.awt.Toolkit$SelectiveAWTEventListener.eventDispatched(Unknown Source)
     at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Unknown Source)
     at java.awt.Toolkit.notifyAWTEventListeners(Unknown Source)
     at java.awt.TrayIcon.dispatchEvent(Unknown Source)
     at java.awt.EventQueue.dispatchEvent(Unknown Source)
     at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.TrayIcon cannot be cast to java.awt.Component
     at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.eventDispatched(Unknown Source)
     at java.awt.Toolkit$SelectiveAWTEventListener.eventDispatched(Unknown Source)
     at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Unknown Source)
     at java.awt.Toolkit.notifyAWTEventListeners(Unknown Source)
     at java.awt.TrayIcon.dispatchEvent(Unknown Source)
     at java.awt.EventQueue.dispatchEvent(Unknown Source)
     at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.run(Unknown Source)Below is my TrayMenu class extending JPopupMenu:
package gui.menus;
import gui.frames.TrayTweetFrame;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.ImageIcon;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import util.Constants;
public class TrayMenu extends JPopupMenu implements ActionListener, MouseListener {
     private JMenuItem exitMenuItem = null;
     private TrayTweetFrame frame = null;
     private JMenuItem minimizeMenuItem = null;
     private JMenuItem restoreMenuItem = null;
     private static final long serialVersionUID = 1L;
      * Constructor
      * @param TrayTweetFrame frame
      * @throws HeadlessException
     public TrayMenu ( TrayTweetFrame frame ) throws HeadlessException {
          this.frame = frame;
          this.initialize();
     } // end constructor
      * This method handles the events.
     public void actionPerformed( ActionEvent e ) {
          // Exit
          if ( e.getSource().equals( getExitMenuItem() ) ) {
               getFrame().exit();
          // Restore or Minimize window
          else if ( e.getSource().equals( getRestoreMenuItem() ) ||
                    e.getSource().equals( getMinimizeMenuItem() ) ) {
               getFrame().minimize();
     } // end method actionPerformed()
      * This method initializes and returns
      * the Exit menu item.
      * @return MenuItem exitMenuItem
     public JMenuItem getExitMenuItem() {
          if ( exitMenuItem == null ) {
               exitMenuItem = new JMenuItem( Constants.MENU_EXIT, new ImageIcon("img/icons/exit.png" ) );
               exitMenuItem.addActionListener( this );
          return exitMenuItem;
     } // end method getExitMenuItem
      * This method returns the frame.
      * @return frame
     public TrayTweetFrame getFrame() {
          return frame;
     } // end method getFrame
      * This method initializes and returns
      * the Minimize menu item.
      * @return MenuItem minimizeMenuItem
     public JMenuItem getMinimizeMenuItem() {
          if ( minimizeMenuItem == null ) {
               minimizeMenuItem = new JMenuItem( Constants.MENU_MINIMIZE, new ImageIcon("img/icons/minimize.png" ) );
               minimizeMenuItem.addActionListener( this );
          return minimizeMenuItem;
     } // end method getMinimizeMenuItem
      * This method initializes and returns
      * the Restore menu item.
      * @return MenuItem restoreMenuItem
     public JMenuItem getRestoreMenuItem() {
          if ( restoreMenuItem == null ) {
               restoreMenuItem = new JMenuItem( Constants.MENU_RESTORE, new ImageIcon("img/icons/maximize.png" ) );
               restoreMenuItem.addActionListener( this );
               restoreMenuItem.setEnabled( false );
          return restoreMenuItem;
     } // end method getRestoreMenuItem
      * This method initializes the menu.
     private void initialize() {
          this.add( getMinimizeMenuItem() );          // Minimize
          this.add( getRestoreMenuItem() );          // Restore
          this.addSeparator();                    // --------
          this.add( getExitMenuItem() );               // Exit
     } // end method initialize
     public void mouseClicked(MouseEvent e) {
          // Check for double-click
          if ( e.getClickCount() == 2 ) {
               // Minimize to the system tray
               getFrame().minimize();
          } // end if
     public void mouseEntered(MouseEvent e) {}
     public void mouseExited(MouseEvent e) {}
     public void mousePressed(MouseEvent e) {}
     public void mouseReleased(MouseEvent e) {
          if ( e.isPopupTrigger() ) {
               this.setLocation( e.getX(), e.getY() );
               this.setInvoker( this );
               this.setVisible( true );
} // end class TrayMenuAm I doing something wrong? Like I said, I'm not casting (at least explicitly..), so I'm not sure why I'm getting a java.lang.ClassCastException error. Normally I can figure out problems like these with Google, but again, when I did Google this, I came across the bug report which describes my issue exactly (but at the same time, left me wondering what the solution is).
Again, any help is appreciated. Thanks again, ejp!