Java SE (Java Platform, Standard Edition)

This is a followup to 9609185 wherein I ask for pointers to help me understand the source of focus-loss behaviour in my JTable's custom cell editor.

I have done some more investigations and it turns out that the focus loss is a more general problem with custom cell editors which call other windows. Even the color-picker demo in the JTable tutorial at http://download.oracle.com/javase/tutorial/uiswing/examples/components/index.html#TableDialogEditDemo has this problem, IF you add a text field or two to the layout BEFORE the table. The only reason the table in the demo doesn't lose the focus when the color-picker comes out is because the table is the only thing in the window!

Here is the demo code, augmented with two text fields, which are admittedly ugly here but which serve the desired purpose:

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import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.TableCellEditor;
import javax.swing.table.TableCellRenderer;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class TableDialogEditDemo extends JPanel {
    public class ColorEditor extends AbstractCellEditor
            implements TableCellEditor,
            ActionListener {
        Color currentColor;
        JButton button;
        JColorChooser colorChooser;
        JDialog dialog;
        protected static final String EDIT = "edit";

        public ColorEditor() {
            //Set up the editor (from the table's point of view), which is a button.
            //This button brings up the color chooser dialog, which is the editor from the user's point of view.
            button = new JButton();
            button.setActionCommand(EDIT);
            button.addActionListener(this);
            button.setBorderPainted(false);

            //Set up the dialog that the button brings up.
            colorChooser = new JColorChooser();
            dialog = JColorChooser.createDialog(button, "Pick a Color", true,  //modal
                    colorChooser, this,  //OK button handler
                    null); //no CANCEL button handler
        }

        /**
         * Handles events from the editor button and from the dialog's OK button.
         */
        public void actionPerformed(ActionEvent e) {
            if (EDIT.equals(e.getActionCommand())) {
                //The user has clicked the cell, so bring up the dialog.
                button.setBackground(currentColor);
                colorChooser.setColor(currentColor);
                dialog.setVisible(true);

                //Make the renderer reappear.
                fireEditingStopped();

            } else { //User pressed dialog's "OK" button
                currentColor = colorChooser.getColor();
            }
        }

        public Object getCellEditorValue() {
            return currentColor;
        }

        public Component getTableCellEditorComponent(JTable table,
                                                     Object value,
                                                     boolean isSelected,
                                                     int row,
                                                     int column) {
            currentColor = (Color) value;
            return button;
        }
    }

    public class ColorRenderer extends JLabel
            implements TableCellRenderer {
        Border unselectedBorder = null;
        Border selectedBorder = null;
        boolean isBordered = true;

        public ColorRenderer(boolean isBordered) {
            this.isBordered = isBordered;
            setOpaque(true);
        }

        public Component getTableCellRendererComponent(
                JTable table, Object color,
                boolean isSelected, boolean hasFocus,
                int row, int column) {
            Color newColor = (Color) color;
            setBackground(newColor);
            if (isBordered) {
                if (isSelected) {
                    if (selectedBorder == null) {
                        selectedBorder = BorderFactory.createMatteBorder(2, 5, 2, 5,
                                table.getSelectionBackground());
                    }
                    setBorder(selectedBorder);
                } else {
                    if (unselectedBorder == null) {
                        unselectedBorder = BorderFactory.createMatteBorder(2, 5, 2, 5,
                                table.getBackground());
                    }
                    setBorder(unselectedBorder);
                }
            }
            return this;
        }
    }

    public TableDialogEditDemo() {
        super(new GridLayout());

        JTextField tf1 = new JTextField("tf1");
        add(tf1);
        JTextField tf2 = new JTextField("tf2");
        add(tf2);

        JTable table = new JTable(new MyTableModel());
        table.setPreferredScrollableViewportSize(new Dimension(500, 70));
        table.setFillsViewportHeight(true);

        JScrollPane scrollPane = new JScrollPane(table);

        table.setDefaultRenderer(Color.class,
                new ColorRenderer(true));
        table.setDefaultEditor(Color.class,
                new ColorEditor());

        add(scrollPane);
    }

    class MyTableModel extends AbstractTableModel {
        private String[] columnNames = {"First Name",
                "Favorite Color",
                "Sport",
                "# of Years",
                "Vegetarian"};
        private Object[][] data = {
                {"Mary", new Color(153, 0, 153),
                        "Snowboarding", new Integer(5), new Boolean(false)},
                {"Alison", new Color(51, 51, 153),
                        "Rowing", new Integer(3), new Boolean(true)},
                {"Kathy", new Color(51, 102, 51),
                        "Knitting", new Integer(2), new Boolean(false)},
                {"Sharon", Color.red,
                        "Speed reading", new Integer(20), new Boolean(true)},
                {"Philip", Color.pink,
                        "Pool", new Integer(10), new Boolean(false)}
        };

        public int getColumnCount() {
            return columnNames.length;
        }

        public int getRowCount() {
            return data.length;
        }

        public String getColumnName(int col) {
            return columnNames[col];
        }

        public Object getValueAt(int row, int col) {
            return data[row][col];
        }

        public Class getColumnClass(int c) {
            return getValueAt(0, c).getClass();
        }

        public boolean isCellEditable(int row, int col) {
            if (col < 1) {
                return false;
            } else {
                return true;
            }
        }

        public void setValueAt(Object value, int row, int col) {
            data[row][col] = value;
            fireTableCellUpdated(row, col);
        }
    }

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TableDialogEditDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JComponent newContentPane = new TableDialogEditDemo();
        newContentPane.setOpaque(true);
        frame.setContentPane(newContentPane);

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

When you come back from choosing a color, tf1 is given the focus, instead of the table. This is because bringing the color picker window to the front causes a focus lost event for the cell editor component; it's temporary, as it should be, so why on earth is the system losing track of who has focus in the window??

I see the following in Window#getMostRecentFocusOwner():

  public Component getMostRecentFocusOwner()
  {
    if (isFocused())
    {
      return getFocusOwner();
    }
    else
    {
      Component mostRecent =
        KeyboardFocusManager.getMostRecentFocusOwner(this);
      if (mostRecent != null)
      {
        return mostRecent;
      }
      else
      {
        return (isFocusableWindow())
               ? getFocusTraversalPolicy().getInitialComponent(this)
               : null;
      }
    }
  }

My app has a custom focus traversal policy, so I'm able to see who is being called, and indeed, getInitialComponent() is being called. Clearly, the KeyboardFocusManager is actually losing track of the fact that the table was focussed at the point where control was transferred to the color picker! This strikes me as completely unreasonable, especially since, as noted, this is a temporary focus loss event, not a permanent one.

I'd be grateful for any wisdom in solving this, since similar behaviour to this little demo -- without focus loss, naturally -- is an essential part of my application.