drag and drop DND click, then move??

[verduka fox]

I am developing a Java application in 1.5 that utilizes drag and drop to move data between two JLists. My question: why is there a delay in moving the items? I need to first click on the item, then click and drag it to the other list. This behavior isn't intuitive; I wouldn't expect to first have to select the item, then click again to move it. I expect to be able to click and drag the item in one movement. I'm sure I'm just missing something. Can anyone please explain?

Code follows. If you compile and run, you should be able to reproduce the behavior I see.

Thanks in advance!

    
package mytest;
 
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
 
import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
 
public class ListDND 
{
   JList listHome;
   JList listVisit;
 
   private JPanel getContent()
   {
      JPanel panel = new JPanel(new GridBagLayout());
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      gbc.fill = GridBagConstraints.BOTH;
      gbc.insets.right = 2;
      gbc.insets.left = 2;
 
      gbc.gridx = 1;
      gbc.gridy = 3;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      panel.add(getHomeMedsComponent(), gbc);
      
      gbc.gridx = 1;
      gbc.gridy = 5;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      panel.add(getVisitMedsComponent(), gbc);
      
      return panel;
   }
 
   private JScrollPane getHomeMedsComponent()
   {
      DefaultListModel listModel = new DefaultListModel();
      listModel.addElement("Home 1");
      listModel.addElement("Home 2");
      listModel.addElement("Home 3");
      listHome = new JList(listModel);
      listHome.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
      listHome.setDragEnabled(true);
      listHome.setTransferHandler(new ListDNDTransferHandler());
      return new JScrollPane(listHome);
   }
 
   private JScrollPane getVisitMedsComponent()
   {
      DefaultListModel listModel = new DefaultListModel();
      listModel.addElement("Visit 1");
      listModel.addElement("Visit 2");
      listModel.addElement("Visit 3");
      listVisit = new JList(listModel);
      listVisit.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
      listVisit.setDragEnabled(true);
      listVisit.setTransferHandler(new ListDNDTransferHandler());
      return new JScrollPane(listVisit);
   }
 
   public static void main(String[] args)
   {
      ListDND test = new ListDND();
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.getContentPane().add(test.getContent());
      f.setSize(600, 400);
      f.setLocation(200, 200);
      f.setVisible(true);
   }
   
}
 

And the TransferHandler:

    
package mytest;
 
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.IOException;
 
import javax.swing.DefaultListModel;
import javax.swing.JComponent;
import javax.swing.JList;
import javax.swing.TransferHandler;
 
class ListDNDTransferHandler extends TransferHandler
{
 
   /**
    * Perform the actual data import.
    */
   public boolean importData(JComponent comp, Transferable t)
   {
      System.out.println("ListDNDTransferHandler.importData 1");
      String data = null;
 
      // If we can't handle the import, bail now.
      // if (!canImport(info)) {
      if (!canImport(comp, t.getTransferDataFlavors()))
      {
         return false;
      }
 
      JList list = (JList) comp;
      DefaultListModel listModel = (DefaultListModel) list.getModel();
      // Fetch the data -- bail if this fails
      try
      {
          data = (String)t.getTransferData(DataFlavor.stringFlavor);
      }
      catch (UnsupportedFlavorException ufe)
      {
         System.out.println("importData: unsupported data flavor: " + ufe.getMessage());
         return false;
      }
      catch (IOException ioe)
      {
         System.out.println("importData: I/O exception: " + ioe.getMessage());
         return false;
      }
 
      String[] values = data.split("\n");
      int index = 0;
      for (int i = 0; i < values.length; i++)
      {
         listModel.add(index++, values[i]);
         list.clearSelection();
      }
      return true;
   }
 
   /**
    * Bundle up the data for export.
    */
   protected Transferable createTransferable(JComponent c)
   {
      JList list = (JList) c;
      String value = (String) list.getSelectedValue();
      return new StringSelection(value);
   }
 
   /**
    * The list handles both copy and move actions.
    */
   public int getSourceActions(JComponent c)
   {
      return MOVE;
   }
 
   /**
    * When the export is complete, remove the old list entry if the action was a
    * move.
    */
   protected void exportDone(JComponent c, Transferable t, int action)
   {
      if (action != MOVE)
      {
         return;
      }
      JList list = (JList) c;
      DefaultListModel model = (DefaultListModel) list.getModel();
      int index = list.getSelectedIndex();
      String data = "";
      try
      {
         data = (String)t.getTransferData(DataFlavor.stringFlavor);
      }
      catch (UnsupportedFlavorException e)
      {
         System.out.println("Exception: " + e.getMessage());
         e.printStackTrace();
      }
      catch (IOException e)
      {
         System.out.println("Exception: " + e.getMessage());
         e.printStackTrace();
      }
      String[] values = data.split("\n");
      for (int i = 0; i < values.length; i++)
      {
         model.remove(index);
      }
      list.clearSelection();
   }
 
   /**
    * We only support importing strings.
    */
   DataFlavor stringFlavor = DataFlavor.stringFlavor;
 
   public boolean canImport(JComponent comp, DataFlavor[] transferFlavors)
   {
      // we only import Strings
      for (int j = 0; j < transferFlavors.length; j++)
      {
         if (stringFlavor.equals(transferFlavors[j]))
         {
            return true;
         }
      }
      return false;
   }
}