Tab and back-tab out of a JTable

Question

Hi There,
I have been working for some time on improving the default behaviour of the tab key within editable JTables. It largely works as required now, but I'm stuck on getting back-tab to leave the table if on row 0, col 0. I register tab and back-tab action in the table's ActionMap that looks like this:     
     class TabAction extends AbstractAction {
          public void actionPerformed(ActionEvent e) {
               if (getRowCount() > 0) {
                    int row = getSelectedRow();
                    int column = getSelectedColumn();
                    if (row < 0 || column < 0) {
                         row = 0;
                         column = 0;
                    do {
                         if (++column >= getColumnCount()) {
                              row++;
                              column = 0;
                    } while (row < getRowCount() && ! isCellTabbable(row, column));
                    if (row < getRowCount()) {
                         changeSelection(row, column, false, false);
                    } else {
                         clearSelection();
                         transferFocus();
               } else {
                    transferFocus();
     class BackTabAction extends AbstractAction {
          public void actionPerformed(ActionEvent e) {
               if (getRowCount() > 0) {
                    int row = getSelectedRow();
                    int column = getSelectedColumn();
                    if (row < 0 || column < 0) {
                         row = getRowCount() - 1;
                         column = getColumnCount() - 1;
                    do {
                         if (--column < 0) {
                              row--;
                              column = getColumnCount() - 1;
                    } while (row >= 0 && ! isCellTabbable(row, column));
                    if (row >= 0) {
                         changeSelection(row, column, false, false);
                    } else {
                         clearSelection();
                         transferFocusBackward();
                         KeyboardFocusManager fm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
                            // fm.upFocusCycle(BTTTable_Editable.this);                         
                         // fm.focusPreviousComponent(BTTTable_Editable.this);
               } else {     
                    // transferFocusBackward();
                    // KeyboardFocusManager fm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
                       // fm.upFocusCycle(BTTTable_Editable.this);                         
                    // fm.focusPreviousComponent(BTTTable_Editable.this);
     }transferFocus() to go to the next screen component works fine - as long as I callsetFocusTraversalPolicyProvider(true); when I create the JTable.
But the backward traversal just doesn't work - instead it does nothing the first time you press back-tab on row 0 col 0, then if you press it again, focus goes onto the last row/col of the table.
As an alternative, I thought maybe I could call the Ctrl-back-tab action, but I can't find that registered in the action map - can anyone tell me how ctrl-back-tab is called and whether I can call that code directly?
Any ideas?
Thanks,
Tim

Answer 1

Where's the rest of your code? What good does posting
the Actions do if we can't execute your code and see
how you've installed the Actions on the table? Who
knows where the mistake is. It may be in the posted
code or it may be in some other code.Well I assume the Action is registered okay because back-tab within the table works fine, and in fact using a debugger I can see that the focus request code (transferFocusBackward) is being called at the right time. I followed it into that code and it appears that it is picking up the tableCellEditor as the "previous" component which is "why" it isn't working right - not that that helps me to fix it.
Anyway, just to confirm, here is a complete standalone testcase:import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.KeyboardFocusManager;
import java.awt.event.ActionEvent;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
* <br>
* <br>
* Created on 14/11/2005 by Tim Ryan
public class TabTable extends JTable implements FocusListener {
     protected KeyStroke TAB = KeyStroke.getKeyStroke(KeyEvent.VK_TAB, 0);
     protected KeyStroke BACK_TAB = KeyStroke.getKeyStroke(KeyEvent.VK_TAB,
               InputEvent.SHIFT_DOWN_MASK);
     protected KeyStroke LEFT_ARROW = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0);
     protected KeyStroke RIGHT_ARROW = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0);
     public TabTable(Object[][] rowData, Object[] columnNames) {
          super(rowData, columnNames);
          initialise();
     public TabTable() {
          super();
          initialise();
     private void initialise() {
          addFocusListener(this);
          InputMap inMap = getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
          ActionMap actionMap = getActionMap();
          inMap.put(LEFT_ARROW, "None");
          inMap.put(RIGHT_ARROW, "None");
          actionMap.put(inMap.get(TAB), new TabAction());
          actionMap.put(inMap.get(BACK_TAB), new BackTabAction());
          setCellSelectionEnabled(true);
          putClientProperty("terminateEditOnFocusLost", Boolean.TRUE);
          setFocusTraversalPolicyProvider(true);
     public void focusGained(FocusEvent e) {
          if (getRowCount() > 0 && getSelectedRow() < 0) {
               editCellAt(0, 0);
               getEditorComponent().requestFocusInWindow();
     public void focusLost(FocusEvent e) {
     public void changeSelection(int row, int column, boolean toggle, boolean extend) {
          super.changeSelection(row, column, toggle, false);
          if (editCellAt(row, column)) {
               getEditorComponent().requestFocusInWindow();
      * This class handles the back-tab operation on the table.
      * It repeatedly steps the selection backwards until the focus
      * ends up on a cell that is allowable (see <code>isCellTabbable()</code>).
      * If already at the end of the table then focus is transferred out
      * to the previous component on the screen.
     class BackTabAction extends AbstractAction {
          public void actionPerformed(ActionEvent e) {
               if (getRowCount() > 0) {
                    int row = getSelectedRow();
                    int column = getSelectedColumn();
                    if (row < 0 || column < 0) {
                         row = getRowCount() - 1;
                         column = getColumnCount() - 1;
                    do {
                         if (--column < 0) {
                              row--;
                              column = getColumnCount() - 1;
                    } while (row >= 0 && ! isCellTabbable(row, column));
                    if (row >= 0) {
                         changeSelection(row, column, false, false);
                    } else {
                         clearSelection();
                         // transferFocusBackward();
                         KeyboardFocusManager.getCurrentKeyboardFocusManager().focusPreviousComponent();
               } else {
                    // transferFocusBackward();
                    KeyboardFocusManager.getCurrentKeyboardFocusManager().focusPreviousComponent();
      * This class handles the tab operation on the table.
      * It repeatedly steps the selection forwards until the focus ends
      * up on a cell that is allowable (see <code>isCellTabbable()</code>).
      * If already at the end of the table then focus is transferred out
      * to the next component on the screen.
     class TabAction extends AbstractAction {
          public void actionPerformed(ActionEvent e) {
               if (getRowCount() > 0) {
                    int row = getSelectedRow();
                    int column = getSelectedColumn();
                    if (row < 0 || column < 0) {
                         row = 0;
                         column = 0;
                    do {
                         if (++column >= getColumnCount()) {
                              row++;
                              column = 0;
                    } while (row < getRowCount() && ! isCellTabbable(row, column));
                    if (row < getRowCount()) {
                         changeSelection(row, column, false, false);
                    } else {
                         clearSelection();
                         transferFocus();
               } else {
                    transferFocus();
      * Some cells can be tabbed to, but are not actually editable.
      * @param row
      * @param column
      * @return
     private boolean isCellTabbable(int row, int column) {
          return (column % 2 == 0);
     public boolean isCellEditable(int row, int column) {
          return (column == 1 || column == 3);
      * @param args
     public static void main(String[] args) {
          JFrame frame = new JFrame("Tables test");
          frame.setName("TablesTest");
          frame.setSize(600, 400);
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JPanel panelMain = new JPanel(new GridBagLayout());
          frame.add(panelMain);
          Object[][] tableData = new Object[2][6];
          Object[] columnHeadings = new Object[] {"H0", "H1", "H2", "H3", "H4", "H5"};
          GridBagConstraints gbc = new GridBagConstraints();
          gbc.anchor = GridBagConstraints.NORTH;
          gbc.insets = new Insets(10, 10, 10, 10);
          JTextField field1 = new JTextField("left", 8);
          field1.setName("left");
          panelMain.add(field1, gbc);
          Dimension tableSize = new Dimension(300, 300);
          BTTTable table3 = new BTTTable_Editable(tableData, columnHeadings);
          table3.setName("Editable");
          JScrollPane scroll3 = new JScrollPane(table3);
          scroll3.setPreferredSize(tableSize);
          panelMain.add(scroll3, gbc);
          JTextField field2 = new JTextField("right", 8);
          field2.setName("right");
          gbc.gridwidth = GridBagConstraints.REMAINDER;
          panelMain.add(field2, gbc);
          frame.setVisible(true);
}I thought it might be the focusGained() code, but commenting that out makes no difference.
And here is the code I would use to go to the
previous component:
KeyboardFocusManager.getCurrentKeyboardFocusManager().
focusPreviousComponent();I tried that too, as you can see from my original post. It gives the same answer.
So the big question is why does the FocusManager think that the "previous" field to the table is an editor component within the table?
Regards,
Tim