Name: sl110371 Date: 07/31/2000


java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, mixed mode)

I submitted this against 1.2, but it vanished without trace. It's
still in 1.3, so I'm submitting it again.

DefaultListSelectionModel.removeIndexInterval(int, int) does not fire a
ListSelectionEvent when it removes selected indices. JTable uses a
DefaultListSelectionModel to model row selection. This means that when a
selected row is removed from a JTable's TableModel, no ListSelectionEvent is
generated to notify listeners of the change in selection.

The following code demonstrates the problem:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;

public class ListModelTest extends JFrame
{
   private JButton deleteButton = new JButton("Delete Row");
   private JLabel rowText = new JLabel("none");
   private JLabel columnText = new JLabel("none");

   private void setupSelectionModels(final ListSelectionModel rowModel, final
ListSelectionModel columnModel)
   {
      // Listen for changes in the row selection and update our interface in
      // response:

      rowModel.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
      rowModel.addListSelectionListener(new ListSelectionListener() {
         public void valueChanged(ListSelectionEvent e)
         {
            if (rowModel.isSelectionEmpty())
            {
               //
               // Bug:
               //
               // Even though the row selection vanishes after we hit the
               // delete button, we never arrive here.
               //

               rowText.setText("none");
               deleteButton.setEnabled(false);
            }
            else
            {
               rowText.setText("" + rowModel.getMinSelectionIndex());
               deleteButton.setEnabled(true);
            }
         }
      });

      // Listen for changes in the column selection:

      columnModel.addListSelectionListener(new ListSelectionListener() {
         public void valueChanged(ListSelectionEvent e)
         {
            if (columnModel.isSelectionEmpty())
            {
               //
               // We never arrive here either (but probably not a bug).
               //

               columnText.setText("none");
            }
            else
            {
               char minColumn = (char) ('A' +
                  columnModel.getMinSelectionIndex());
               char maxColumn = (char) ('A' +
                  columnModel.getMaxSelectionIndex());
               String text = "" + minColumn;
               if (minColumn != maxColumn)
                  text += "..." + maxColumn;
               columnText.setText(text);
            }
         }
      });
   }

   /**
    * Setup <i>deleteButton</i> to delete the the minimum selected row
    * of <i>table</i>
    */

   private void setupDeleteButton(JButton deleteButton, final JTable table)
   {
      deleteButton.setEnabled(false);

      deleteButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e)
         {
            int row = table.getSelectionModel().getMinSelectionIndex();
            if (row == -1)
            {
               // We shouldn't ever arrive here because our row selection
               // listener disables the delete button when there is no
               // selection.

               System.out.println("Arrrrgh! No row to delete!");
            }
            else
            {
               // This is where the trouble starts. Removing the selected row
               // changes the selection, but it doesn't notify the selection
               // listeners.

               ((DefaultTableModel) table.getModel()).removeRow(row);
            }
         }
      });
   }

   /**
    * Interface.
    */

   public ListModelTest()
   {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e)
         {
            System.exit(0);
         }
      });

      JLabel columnLabel = new JLabel("Selected Column: ");
      JLabel rowLabel = new JLabel("Selected Row: ");
      rowLabel.setPreferredSize(columnLabel.getPreferredSize());
      JTable table = new JTable(100, 5);
      table.setCellSelectionEnabled(true);
      JScrollPane tablePane = new JScrollPane(table);

tablePane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
      setupSelectionModels(table.getSelectionModel(),
table.getColumnModel().getSelectionModel());
      setupDeleteButton(deleteButton, table);

      // layout:

      Box b1 = Box.createVerticalBox();
      Box b2 = Box.createHorizontalBox();
      Box b3 = Box.createHorizontalBox();
      Box b4 = Box.createHorizontalBox();

      getContentPane().add(tablePane);
      getContentPane().add(b1, BorderLayout.SOUTH);
      b1.add(b2);
      b1.add(b3);
      b1.add(b4);
      b2.add(rowLabel);
      b2.add(Box.createHorizontalStrut(5));
      b2.add(rowText);
      b2.add(Box.createHorizontalGlue());
      b3.add(columnLabel);
      b3.add(Box.createHorizontalStrut(5));
      b3.add(columnText);
      b3.add(Box.createHorizontalGlue());
      b4.add(Box.createHorizontalGlue());
      b4.add(deleteButton);
      setBounds(new Rectangle(20, 20, 300, 200));
   }

   /**
    * Go.
    */

   public static void main(String[] argv)
   {
      new ListModelTest().show();
   }
}

The offending code is in DefaultListSelectionModel:

    /**
     * Remove the indices in the interval index0,index1 (inclusive) from
     * the selection model. This is typically called to sync the selection
     * model width a corresponding change in the data model. Note
     * that (as always) index0 need not be <= index1.
     */
   public void removeIndexInterval(int index0, int index1)
   {
      int rmMinIndex = Math.min(index0, index1);
      int rmMaxIndex = Math.max(index0, index1);
      int gapLength = (rmMaxIndex - rmMinIndex) + 1;

      /* Shift the entire bitset to the left to close the index0, index1
       * gap.
       */
      for(int i = rmMinIndex; i <= maxIndex; i++) {
         setState(i, value.get(i + gapLength));
      }

      // Woops... just stomped on part of the selection and didn't
      // notify anyone.
   }

This _is_ a bug. DefaultListSelectionModel is incomplete in the formal
sense: It is impossible to track the state of a DefaultListSelectionModel
by observation.
(Review ID: 107799)
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