How do I drag and drop a row in a JTable?

Question

How do you setup a JTable to be able to drag a row to a different index in the table. For example if I have 5 rows and I want to drag the 4th row to the 2nd position?

Answer 1

The following allows JTable re-ordering of a single dragged row:

  table.setDragEnabled(true);
  table.setDropMode(DropMode.INSERT_ROWS);
  table.setTransferHandler(new TableRowTransferHandler(table)); 

Your TableModel should implement the following to allow for re-ordering:

public interface Reorderable {
   public void reorder(int fromIndex, int toIndex);
}

This TransferHandler class handles the drag & drop, and calls reorder() on your TableModel when the gesture is completed.

/**
 * Handles drag & drop row reordering
 */
public class TableRowTransferHandler extends TransferHandler {
   private final DataFlavor localObjectFlavor = new ActivationDataFlavor(Integer.class, "application/x-java-Integer;class=java.lang.Integer", "Integer Row Index");
   private JTable           table             = null;

   public TableRowTransferHandler(JTable table) {
      this.table = table;
   }

   @Override
   protected Transferable createTransferable(JComponent c) {
      assert (c == table);
      return new DataHandler(new Integer(table.getSelectedRow()), localObjectFlavor.getMimeType());
   }

   @Override
   public boolean canImport(TransferHandler.TransferSupport info) {
      boolean b = info.getComponent() == table && info.isDrop() && info.isDataFlavorSupported(localObjectFlavor);
      table.setCursor(b ? DragSource.DefaultMoveDrop : DragSource.DefaultMoveNoDrop);
      return b;
   }

   @Override
   public int getSourceActions(JComponent c) {
      return TransferHandler.COPY_OR_MOVE;
   }

   @Override
   public boolean importData(TransferHandler.TransferSupport info) {
      JTable target = (JTable) info.getComponent();
      JTable.DropLocation dl = (JTable.DropLocation) info.getDropLocation();
      int index = dl.getRow();
      int max = table.getModel().getRowCount();
      if (index < 0 || index > max)
         index = max;
      target.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
      try {
         Integer rowFrom = (Integer) info.getTransferable().getTransferData(localObjectFlavor);
         if (rowFrom != -1 && rowFrom != index) {
            ((Reorderable)table.getModel()).reorder(rowFrom, index);
            if (index > rowFrom)
               index--;
            target.getSelectionModel().addSelectionInterval(index, index);
            return true;
         }
      } catch (Exception e) {
         e.printStackTrace();
      }
      return false;
   }

   @Override
   protected void exportDone(JComponent c, Transferable t, int act) {
      if ((act == TransferHandler.MOVE) || (act == TransferHandler.NONE)) {
         table.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
      }
   }

}

Answer 2

Check out the drag and drop section of the Java Tutorial. There are some examples on how to implement this for JTable.

Answer 3

I like Soley's modifications, but his code relies on an external library, and I'm not sure where he got it from, so I re-wrote it so that you don't need the TableUtil class...

 @Override
   public boolean importData(TransferHandler.TransferSupport info) {
     JTable target = (JTable) info.getComponent();
        JTable.DropLocation dl = (JTable.DropLocation) info.getDropLocation();
        int index = dl.getRow();
        int max = table.getModel().getRowCount();
        if (index < 0 || index > max) {
            index = max;
        }
        target.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));

        try {
            Integer rowFrom = (Integer) info.getTransferable().getTransferData(localObjectFlavor);
            if (rowFrom != -1 && rowFrom != index) {

                int[] rows = table.getSelectedRows();
                int iter = 0;
                for (int row : rows) {
                    if (index > row) {
                        index--;
                        ((Reorderable) table.getModel()).reorder(row - iter, index);
                    }

                    else {
                        ((Reorderable) table.getModel()).reorder(row, index);
                    }
                    index++;
                    iter++;
                }

                target.getSelectionModel().addSelectionInterval(index, index);

                return true;
            }

      } catch (Exception e) {
            String error = e.getMessage();
            JOptionPane.showMessageDialog(null, error, "Error", JOptionPane.ERROR_MESSAGE);
      }
      return false;
   }