Dnd in JScrollPane broken in 1.4??

Question

Hello,
I have been trying to enable DnD in an application but have encountered many hurdles, including what appears to be broken DnD support for components within scroll panes. I've filed a bug report in Sun's database, but was hoping perhaps someone else has encountered this problem before.
The problem arises when the user performs a DnD operation, and drags an object over a scroll pane. This example program demonstrates the bug. Select a row in the table, then drag it over the empty portion of the scroll pane. You should see a stack trace thrown to the console.
Has anybody encountered this bug before, and if so, are there any known workarounds?
- Aaron
public class ViewportTransferHandlerDemo implements Runnable {
  public static void main(String[] args) {
    SwingUtilities.invokeLater(new ViewportTransferHandlerDemo());
  public void run() {
    JTable table = new JTable();
    table.setModel(new DefaultTableModel(new String[][] { { "Apple" }, { "Banana" }, { "Cherry" } }, new String[] { "Fruits" }));
    table.setDragEnabled(true);
    table.setTransferHandler(new TransferHandler() {
      protected Transferable createTransferable(JComponent c) {
        JTable t = (JTable) c;
        return new StringSelection((String) t.getValueAt(t.getSelectedRow(), 0));
      public boolean importData(JComponent comp, Transferable t) {
        JTable table = (JTable) comp;
        DefaultTableModel model = (DefaultTableModel) table.getModel();
        try {
          model.setValueAt(t.getTransferData(DataFlavor.stringFlavor), Math.max(0, table.getSelectedRow()), 0);
          return true;
        } catch (UnsupportedFlavorException e) {
          throw new RuntimeException(e);
        } catch (IOException e) {
          throw new RuntimeException(e);
      public int getSourceActions(JComponent c) {
        return COPY_OR_MOVE;
      public boolean canImport(JComponent comp, DataFlavor[] transferFlavors) {
        return true;
    JFrame frame = new JFrame();
    frame.getContentPane().setLayout(new BorderLayout());
    JScrollPane scrollPane = new JScrollPane();
    scrollPane.setViewportView(table);
    frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
    SwingUtilities.updateComponentTreeUI(frame);
    frame.pack();
    frame.show();
}

Answer 1

I always return true to keep the example super-simple.
The transferhandler is only assigned to the table. The table serves as both the drag source and the drop target. If you play with this example, you can drag from one row in the table to another row in the table, and it works O.K.
If i were concerned about making the example more robust, I would probably do some type checking in the canImport method, but for this example I just wanted to keep the line count down.