JComboBox in a JTable

[trinity jecob]

I have a Jcombobox which appears in a column of a JTable. The values are getting initialized when the table gets displayed. But the combo box doesn't displayed unless you don't click on the column containing the combo box.

Now I want to implement two more things in it

1. When I will traverse through the table with tab key and reach to the combo box column, the combo should get displayed without clcking with the mouse.
2. After getting displyed, if I typed some characters, the value in combo box starting with that character should get automatically displayed.

I tried trapping the focus & key event of the combo box but it's not working.
Please help.

Thanks in advance

[Craig Wood]

...the combo should get displayed without clcking with the mouse.
The default behavior with the tab key seems to close the combo popup and I wasn't able to find an easy way around it. I tried working with keyStrokes in InputMaps with no success. There may be a way to do this with ancestor InputMap/ActionMaps and keyStrokes. If not, you may have to write some plaf code. You can open it with either the space bar or the down arrow button once you have tabbed into it. And navigating with the arrow buttons works okay.
if I typed some characters, the value in combo box starting with that character should get automatically displayed
This is provided for us in the JComboBox class and is handled by its nested class DefaultKeySelectionManager (see source code). The code below uses it. If this doesn't meet your needs you can make your own class to implement the JComboBox.KeySelectionManager nested interface and set it on the comboBox editor component (indicated below).
Although I don't count this as completely successful (tab popup issue) it may be useful to you.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import javax.swing.table.*;
 
public class ComboTable {
JTable table;
    private JScrollPane getContent() {
        int rows = 4, cols = 3;
        String[] colIds = new String[cols];
        Object[][] data = new Object[rows][cols];
        String[] comboItems = { "a item", "b item", "c item", "d item" };
        for(int j = 0; j < rows; j++) {
            for(int k = 0; k < cols; k++) {
                if(j == 0)
                    colIds[k] = "column " + (k+1);
                if(j == 0 && k == 1)
                    data[j][k] = comboItems[0];
                else
                    data[j][k] = "row" + (j+1) + " col" + (k+1);
            }
        }
        table = new JTable(new DefaultTableModel(data, colIds));
        table.setCellSelectionEnabled(true);
        table.setSurrendersFocusOnKeystroke(true);
        TableColumn col = table.getColumnModel().getColumn(1);
        col.setCellRenderer(new ComboRenderer(comboItems));
        col.setCellEditor(new ComboEditor(comboItems));
        SelectionListener sl = new SelectionListener(table);
        table.getSelectionModel().addListSelectionListener(sl);
        table.getColumnModel().getSelectionModel().addListSelectionListener(sl);
        return new JScrollPane(table);
    }
 
    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(new ComboTable().getContent());
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class ComboRenderer implements TableCellRenderer {
    JLabel label;
    JComboBox comboBox;
    protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1);
 
    public ComboRenderer(String[] items) {
        label = new JLabel();
        label.setOpaque(true);
        label.setBorder(noFocusBorder);
        comboBox = new JComboBox(items);
        //comboBox.setKeySelectionManager(Your_Selection_Manager);
        Font font = UIManager.getFont("Table.font");
        label.setFont(font);
        comboBox.setFont(font);
    }
 
    /** Copied from DefaultTableCellRenderer source code */
    public Component getTableCellRendererComponent(JTable table,
                                                   Object value,
                                                   boolean isSelected,
                                                   boolean hasFocus,
                                                   int row, int column) {
        JComponent component;
        if(row == 0 && column == 1) {
            comboBox.setSelectedItem(value);
            component = comboBox;
        }
        else {
            label.setText((String)value);
            component = label;
        }
        if (isSelected) {
            component.setForeground(table.getSelectionForeground());
            component.setBackground(table.getSelectionBackground());
        } else {
            component.setForeground(table.getForeground());
            component.setBackground(table.getBackground());
        }
        if(component == label) {
            if(hasFocus) {
                label.setBorder(UIManager.getBorder("Table.focusCellHighlightBorder"));
                if (!isSelected && table.isCellEditable(row, column)) {
                    Color col = UIManager.getColor("Table.focusCellForeground");
                    if (col != null) {
                        label.setForeground(col);
                    }
                    col = UIManager.getColor("Table.focusCellBackground");
                    if (col != null) {
                        label.setBackground(col);
                    }
                }
            } else {
                label.setBorder(noFocusBorder);
            }
        }
        return component;
    }
}
 
class ComboEditor extends AbstractCellEditor implements TableCellEditor {
    JTextField textField;
    JComboBox comboBox;
    Component component;
 
    public ComboEditor(String[] items) {
        textField = new JTextField();
        comboBox = new JComboBox(items);
    }
 
    public Component getTableCellEditorComponent(JTable table,
                                                 Object value,
                                                 boolean isSelected,
                                                 int row, int column) {
        if(row == 0 && column == 1) {
            comboBox.setSelectedItem(value);
            component = comboBox;
        }
        else {
            textField.setText((String)value);
            component = textField;
        }
        return component;
    }
 
    public Object getCellEditorValue() {
        if(component == textField)
            return textField.getText();
        else
            return comboBox.getSelectedItem();
    }
}
 
class SelectionListener implements ListSelectionListener {
    JTable table;
 
    public SelectionListener(JTable table) {
        this.table = table;
    }
 
    public void valueChanged(ListSelectionEvent e) {
        if(!e.getValueIsAdjusting()) {
            int col = table.getSelectedColumn();
            int row = table.getSelectedRow();
            Component c;
            if(row == 0 && col == 1) {
                TableCellEditor editor = table.getCellEditor(row, col);
                c = editor.getTableCellEditorComponent(table,
                                                       table.getValueAt(row, col),
                                                       true, row, col);
                JComboBox combo = (JComboBox)c;
                table.editCellAt(row, col);
                combo.setPopupVisible(true);
            }
        }
    }
}