thejavashop.net

I recently was asked to add a column to an existing JTable to display a list of data using a JComboBox. Each row has its own set of data to display. All examples of JComboBox usage within a JTable I could find was for a set of data to be displayed for every row.

In order to see the combobox when both clicking it (editing) and viewing I had to create both a TableCellEditor and a TableCellRenderer.

public class ComboEditor
    extends AbstractCellEditor
    implements TableCellEditor {
    private JComboBox cb = new JComboBox();

    public Component getTableCellEditorComponent(JTable table,
            Object value,
            boolean isSelected,
            int row,
            int column) {
        if (value instanceof String[]) {
            DefaultComboBoxModel m = new DefaultComboBoxModel((String[]) value);
            cb.setModel(m);
            return cb;
        } else {
            return null;
        }
    }

    public Object getCellEditorValue() {
        return cb.getSelectedItem();
    }
}

public class ComboCellRenderer extends DefaultTableCellRenderer {

    /** Creates a new instance of MusicCellRenderer */
    public ComboCellRenderer() {
        setOpaque(false);
        setHorizontalAlignment(SwingConstants.LEFT);
    }

    @Override
    public Component getTableCellRendererComponent(
            JTable table,
            Object value,
            boolean isSelected,
            boolean hasFocus,
            int row,
            int column) {

        if (value instanceof String[]) {
            //don't actually create a new one every time if you don't need to
            final JComboBox cb = new JComboBox(((String[]) value));
            cb.setEditable(false);
            cb.addActionListener(new ActionListener() {

                public void actionPerformed(ActionEvent e) {
                    cb.setSelectedIndex(0);
                }
            });
            setColors(cb, row, isSelected);
            cb.setOpaque(true);
            cb.setFont(table.getFont());
            return cb;
        } else {
            try {
                setText(value.toString());
            } catch (Exception e) {
                setText(null);
            }
        }
        setFont(table.getFont());
        setOpaque(true);
        setColors(this, row, isSelected);
        return this;
    }

I was able to see the comboboxes in the table couldn’t interact with them to get them to drop down. In order to do this I needed to make that column editable by overriding the isCellEditable method.

@Override
public boolean isCellEditable(int row, int col) {
    if (col == COLUMN_COMBO) {
         return true;
    }
    return false;
}

I hate posts that do not include runnable source so here you go.

Source

I am certainly going to tweak this code before I’m done for both memory usage and performance.