Drag and Drop Export Done is called too soon...

Question

Hi,
I am trying to drag and drop a JLabel from a JPanel into another JPanel. I am no where near to figuring it out, but just for starters I notice that the exportDone() method is called in my custom TransferHandler immediately when the drag begins. Even stranger, createTransferable() is never called. (I am comparing my code to the DragPictureDemo that I found online). The question is, why is exportDone called immediately? Code below. Thanks. (BTW, any other suggestions about what I'm trying to do would be appreciated. I'm not confident in the direction I'm taking here... have yet to understand the Swing DnD mechanism...)
From DragPictureDemo, I notice that createTransferable and exportAsDrag are called immediately upon drag, and exportDone is called at the drop.
Here is my code: First, the main class Testola.java:
* Created on Oct 31, 2007
* Copyright 2006 Michael Anthony Schwager.
* This software comes without warranty or applicability for any purpose.
* Rights granted for any use.
package testola;
import javax.swing.*;
import java.awt.*;
public class Testola implements Runnable {
      * @param args
     public void run() {
          /*char[] stdout_arr={};
          String blah;
          blah=new String(stdout_arr, 0, 0);
          StringBuffer buf=null;
          System.out.println("Hello world." + " wow" + null + "<-null");*/
          // --------- FRAME ---------
          JFrame frame=new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setBounds(30,30,500,400);
        JDesktopPane dtp=new JDesktopPane();
        frame.getContentPane().add(dtp);
        // First Internal Frame; false means no close box.
        JInternalFrame jif=new JInternalFrame("One", true, false, true, true     ); //jif.setBounds(0,0,100,50);
        DnDJPanel contentPanel=new DnDJPanel(); contentPanel.setBackground(new Color(255,255,180));
        contentPanel.setLayout(null);
        // Then JLabels, first 1
        JLabel test1=new JLabel("test1!"); test1.setBounds(0, 0, 50, 20);
        test1.setBorder(BorderFactory.createLineBorder(Color.RED));
        //test1.setTransferHandler(new JComponentTransferHandler());
        contentPanel.add(test1);
        // 2
        JLabel test2=new JLabel("test2!"); test2.setBounds(10, 30, 50, 20);
        test2.setBorder(BorderFactory.createLineBorder(Color.GREEN));
        //test1.setTransferHandler(new JComponentTransferHandler());
        contentPanel.add(test2);
        // Finalize Frame
        contentPanel.setBounds(0,0,250,140);
        contentPanel.setTransferHandler(new JComponentTransferHandler());
        contentPanel.setVisible(true);
        jif.setBounds(10,10,250,140);
        jif.setContentPane(contentPanel);
        jif.setVisible(true);
        // Second Internal Frame
        DnDJInternalFrame jif2=new DnDJInternalFrame("Two", true, false, true, true     );
        // JPanel and jtextfield to add to Frame2
        // Finalize Frame2
        jif2.getContentPane().setLayout(null);
        jif2.setBounds(120,150,200,155);
        jif2.setVisible(true);
        dtp.add(jif);
        dtp.add(jif2);
        try {jif.setIcon(false);} catch (Exception e) {System.err.println("setIcon exception");}
          frame.setVisible(true);
     public static void main(String[] args) {
          Testola testola=new Testola();
          try {EventQueue.invokeAndWait(testola);} catch (Exception e) { System.out.println(e);};
          //testola.run();
          System.out.println("Exit");
}Now, my JComponentTransferHandler.java:
* Created on Apr 12, 2008
* Copyright 2006 Michael Anthony Schwager.
* This file is part of testola.
* testola is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* testola is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*  (You should have received a copy of the GNU General Public License
*  along with testola; if not, write to the Free Software
*  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
package testola;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.event.InputEvent;
import javax.swing.JComponent;
import javax.swing.TransferHandler;
public class JComponentTransferHandler extends TransferHandler {
     public JComponentTransferHandler() {
          super();
     public JComponentTransferHandler(String property) {
          super(property);
     public void exportDone(JComponent source, Transferable data, int action) {
          super.exportDone(source, data, action);
          System.out.println("Export is done!");
     public boolean importData(JComponent comp, Transferable t) {
          boolean res;
          res=super.importData(comp, t);
          System.out.println("Import is done! " + res);
          return res;
     public boolean canImport(JComponent comp, DataFlavor[] transferFlavors) {
          boolean res;
          res=super.canImport(comp, transferFlavors);
          System.out.println("Can import: " + res);
          return res;
    public void exportAsDrag(JComponent comp, InputEvent e, int action) {
         super.exportAsDrag(comp, e, action);
         System.out.println("Export as drag: " + comp.getClass().getName());
    protected Transferable createTransferable(JComponent c) {
        System.out.println("createTransferable, arg: " + c.getClass().getName());
         Transferable t=super.createTransferable(c);
        return t;
}Edited by: Hushpuppy on Apr 13, 2008 7:59 PM
Edited by: Hushpuppy on Apr 13, 2008 8:02 PM
Edited by: Hushpuppy on Apr 13, 2008 8:13 PM

Answer 1

No idea whether this will be helpful, but exportDone() is not called immediately if you remove the call to super.exportAsDrag.
db
edit Since your earlier post, I've been trying to teach myself Swing DnD, but am finding the documentation confusing and the tutorials primitive... I'd reached a conclusion, which has every chance of being wrong, that I should call createTransferable from exportAsDrag. FWIW these are the methods as of now -- nothing works :-(   @Override
   public void exportAsDrag(JComponent comp, InputEvent e, int action) {
      // count is a instance field to monitor repeated calls
      System.out.println(count + ". " + "exportAsDrag"); count++;
      //super.exportAsDrag(comp, e, action);
      // dragSource is a instance field of type Container
      dragSource = comp.getParent();
      createTransferable(comp);
   @Override
   protected Transferable createTransferable(JComponent child) {
      System.out.println(count + ". " + "createTransferable"); count++;
      // ComponentHandler implements Transferable
      Transferable t = new ComponentHandler(child);
      return t;
   }The commented line is from testing a possible cause of your problem, since my code never gets as far as exportDone() :-(
Edited by: Darryl.Burke