- Part 2

JTextArea Cell Editor TAB Key Traversal To Next Cell In JTable

January 28, 2010 by blogmeister·2 Comments

By default, pressing the TAB key in a JTextArea will insert a tab character instead of transferring focus to the next focusable component. But if your JTextArea is a cell editor within a JTable, and you want the TAB key to transfer to the next cell on an on, what I did was add a KeyListener to the JTextArea and capture the TAB key event when pressed, then calling the JTable changeSelection() method to transfer focus to the next cell.

If the focus was on the last column of a row, it will check if there is another row next to it. If there is, focus will be transferred to the next row on the first column and so on and so forth. Here is the source code for my TextAreaCellEditor class.

If you want the TextAreaCellEditor class to implement trapping the TAB key event, just supply a boolean parameter true to the constructor.

public class TextAreaCellEditor extends AbstractCellEditor implements TableCellEditor, KeyListener {
    private JTextArea textArea;
    private JScrollPane scrollPane;
    private JTable table;
    private boolean disableTabKey;
    public TextAreaCellEditor() {
        init();
    }
    public TextAreaCellEditor(boolean disableTabKey) {
        this.disableTabKey = disableTabKey;
        init();
    }
    private void init() {
        textArea = new JTextArea();
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        textArea.setRows(3);
        scrollPane = new JScrollPane(textArea);
        scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scrollPane.addFocusListener(new FocusAdapter() {
            @Override
            public void focusGained(FocusEvent fe) {
                textArea.requestFocusInWindow();
                textArea.selectAll();
            }
        });
        if (disableTabKey) textArea.addKeyListener(this);
    }
    @Override
    public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
        textArea.setText(value.toString());
        if (this.table == null) this.table = table;
        table.setRowHeight(textArea.getRows() * 20);
        return scrollPane;
    }
    @Override
    public Object getCellEditorValue() { return textArea.getText(); }
    @Override
    public void keyTyped(KeyEvent e) { }
    @Override
    public void keyPressed(KeyEvent ke) {
        System.out.println(table.getEditingRow() +","+table.getEditingColumn());
        // tab key will transfer focus to next cell
        if (disableTabKey && ke.getKeyCode() == KeyEvent.VK_TAB && !ke.isShiftDown()) {
            ke.consume();
            int column = table.getEditingColumn();
            int row = table.getEditingRow();
            if ((column + 1)  >= table.getColumnCount()) {
                // if column is last column, check if there is next row
                if ((row + 1) >= table.getRowCount()) row = -1;
                else {
                    row++;
                    column = 0;
                }
            } else column++;
            if (row > -1 && column > -1)
                table.changeSelection(row, column, false, false);
            return;
        }
    }
    @Override
    public void keyReleased(KeyEvent e) { }
}

public class TextAreaCellEditor extends AbstractCellEditor implements TableCellEditor, KeyListener {

private JTextArea textArea;

private JScrollPane scrollPane;

private JTable table;

private boolean disableTabKey;

public TextAreaCellEditor() {

init();

}

public TextAreaCellEditor(boolean disableTabKey) {

this.disableTabKey = disableTabKey;

init();

}

private void init() {

textArea = new JTextArea();

textArea.setLineWrap(true);

textArea.setWrapStyleWord(true);

textArea.setRows(3);

scrollPane = new JScrollPane(textArea);

scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

scrollPane.addFocusListener(new FocusAdapter() {

@Override

public void focusGained(FocusEvent fe) {

textArea.requestFocusInWindow();

textArea.selectAll();

}

});

if (disableTabKey) textArea.addKeyListener(this);

}

@Override

public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {

textArea.setText(value.toString());

if (this.table == null) this.table = table;

table.setRowHeight(textArea.getRows() * 20);

return scrollPane;

}

@Override

public Object getCellEditorValue() { return textArea.getText(); }

@Override

public void keyTyped(KeyEvent e) { }

@Override

public void keyPressed(KeyEvent ke) {

System.out.println(table.getEditingRow() +","+table.getEditingColumn());

// tab key will transfer focus to next cell

if (disableTabKey && ke.getKeyCode() == KeyEvent.VK_TAB && !ke.isShiftDown()) {

ke.consume();

int column = table.getEditingColumn();

int row = table.getEditingRow();

if ((column + 1) >= table.getColumnCount()) {

// if column is last column, check if there is next row

if ((row + 1) >= table.getRowCount()) row = -1;

else {

row++;

column = 0;

}

} else column++;

if (row > -1 && column > -1)

table.changeSelection(row, column, false, false);

return;

}

@Override

public void keyReleased(KeyEvent e) { }

}

Focus Traversal In JTable Using TAB Key

January 28, 2010 by blogmeister·3 Comments

Focus traversal from cell to cell in a JTable seems to be a very interesting topic. I scoured the internet looking for a solution and it was not easy. People suggested about focus traversal among others which did not work. One person in a forum mentioned overriding the changeSelection method of the JTable that made it work.

public void changeSelection(final int row, final int column, boolean toggle, boolean extend)  {
    super.changeSelection(row, column, toggle, extend);
    if (editCellAt(row, column)) {
        getEditorComponent().requestFocusInWindow();
    }
}

public void changeSelection(final int row, final int column, boolean toggle, boolean extend) {

super.changeSelection(row, column, toggle, extend);

if (editCellAt(row, column)) {

getEditorComponent().requestFocusInWindow();

}

That’s it. Whenever you press the TAB key if the JTable has focus, the focus will transfer to the next cell. If your cell has an editor associated to it and if the editor returned is a container like a JPanel, you can modify code in your cell editor class and add a FocusListener to the panel object while adding code in the focusGained() method and call requestFocusInWindow() to the Swing component that you want to receive focus.

panel.addFocusListener(new FocusAdapter() {
    @Override
    public void focusGained(FocusEvent fe) {
        textfield.requestFocusInWindow();
        textfield.selectAll();
    }
});

panel.addFocusListener(new FocusAdapter() {

@Override

public void focusGained(FocusEvent fe) {

textfield.requestFocusInWindow();

textfield.selectAll();

}

});

JComboBox CellEditor And “component must be showing on the screen to determine its location” Error

January 28, 2010 by blogmeister·2 Comments

If you use a JComboBox as a cell editor in a JTable and you get this error message “component must be showing on the screen to determine its location”, chances are your cell editor is inherited from DefaultCellEditor. Thomas Bang saved us all the trouble in trying to figure out how to make a workaround for this problem by creating a ComboBoxCellEditor class inheriting from AbstractCellEditor.

Pretty cool. This class actually did the trick.

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.Serializable;
import javax.swing.AbstractCellEditor;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.table.TableCellEditor;
public class ComboBoxPaneledCellEditor extends AbstractCellEditor implements ActionListener, TableCellEditor, Serializable {
    private JComboBox comboBox;
    public ComboBoxPaneledCellEditor(JComboBox comboBox) {
        this.comboBox = comboBox;
        this.comboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
        // hitting enter in the combo box should stop cellediting (see below)
        this.comboBox.addActionListener(this);
    }
    private void setValue(Object value) {
        comboBox.setSelectedItem(value);
    }
    @Override
    public void actionPerformed(java.awt.event.ActionEvent e) {
        // Selecting an item results in an actioncommand "comboBoxChanged".
        // We should ignore these ones.
        // Hitting enter results in an actioncommand "comboBoxEdited"
        if(e.getActionCommand().equals("comboBoxEdited")) {
            stopCellEditing();
        }
    }
    // Implementing CellEditor
    @Override
    public Object getCellEditorValue() {
        return comboBox.getSelectedItem();
    }
    @Override
    public boolean stopCellEditing() {
        if (comboBox.isEditable()) {
            // Notify the combo box that editing has stopped (e.g. User pressed F2)
            comboBox.actionPerformed(new ActionEvent(this, 0, ""));
        }
        fireEditingStopped();
        return true;
    }
    @Override
    public Component getTableCellEditorComponent(javax.swing.JTable table, Object value, boolean isSelected, int row, int column) {
        setValue(value);
        return comboBox;
    }
}

import java.awt.Component;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.Serializable;

import javax.swing.AbstractCellEditor;

import javax.swing.JComboBox;

import javax.swing.JComponent;

import javax.swing.table.TableCellEditor;

public class ComboBoxPaneledCellEditor extends AbstractCellEditor implements ActionListener, TableCellEditor, Serializable {

private JComboBox comboBox;

public ComboBoxPaneledCellEditor(JComboBox comboBox) {

this.comboBox = comboBox;

this.comboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);

// hitting enter in the combo box should stop cellediting (see below)

this.comboBox.addActionListener(this);

}

private void setValue(Object value) {

comboBox.setSelectedItem(value);

}

@Override

public void actionPerformed(java.awt.event.ActionEvent e) {

// Selecting an item results in an actioncommand "comboBoxChanged".

// We should ignore these ones.

// Hitting enter results in an actioncommand "comboBoxEdited"

if(e.getActionCommand().equals("comboBoxEdited")) {

stopCellEditing();

}

// Implementing CellEditor

@Override

public Object getCellEditorValue() {

return comboBox.getSelectedItem();

}

@Override

public boolean stopCellEditing() {

if (comboBox.isEditable()) {

// Notify the combo box that editing has stopped (e.g. User pressed F2)

comboBox.actionPerformed(new ActionEvent(this, 0, ""));

}

fireEditingStopped();

return true;

}

@Override

public Component getTableCellEditorComponent(javax.swing.JTable table, Object value, boolean isSelected, int row, int column) {

setValue(value);

return comboBox;

}

Tech Tips & Tricks

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Month: January 2010

JTextArea Cell Editor TAB Key Traversal To Next Cell In JTable

Focus Traversal In JTable Using TAB Key

JComboBox CellEditor And “component must be showing on the screen to determine its location” Error