Need help creating custom ComboBoxEditor

[Matt Senecal]

Has anyone ever created a custom ComboBoxEditor to display JLabels w/ icons in a JComboBox? I'm looking at the methods in the ComboBoxEditor interface, but I'm not sure how to override getEditorComponent() to return what I want.

[Nathan Pruett]

You should be looking more at the setRenderer( ListCellRenderer ) method... The ListCellRenderer renders the choices in the pull down combo box list. The ComboBoxEditor renders the editing area in an editable combo box. If you do override ListCellRenderer to show an icon and text in a JLabel, then you can override ComboBoxEditor to be a JPanel that holds a JLabel with an icon and a JTextField to edit the text...

Here's a short program that shows this...

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
    
public class NewComboTest extends JFrame {
    
    private JComboBox cb;
    private static final Object[] comboContents = {
        "First", "Second", "Third", "Fourth", "Fifth"
    };
    
    public NewComboTest() {
        super( "New Combo Test" );
        cb = new JComboBox();
        cb.setRenderer( new NewComboRenderer() );
        cb.setEditor( new NewComboEditor() );
        cb.setEditable( true );
        for ( int i = 0; i < comboContents.length; i++ ) {
            cb.addItem( comboContents[ i ] );
        }
        JPanel p = new JPanel();
        p.add( cb );
        getContentPane().add( p );
        setSize( 300, 300 );
        setDefaultCloseOperation( EXIT_ON_CLOSE );
        setVisible( true );
    }
    
    public static void main( String[] arg ) {
        new NewComboTest();
    }
    
    private class NewComboEditor extends JPanel implements ComboBoxEditor {
        JTextField tf;
        JLabel l;
        public NewComboEditor() {
            tf = new JTextField( "" );
            tf.setBackground( Color.white );
            tf.setForeground( Color.red );
            l = new JLabel( new RedDot() );
            setBackground( Color.white );
            setForeground( Color.red );
            setLayout( new BorderLayout() );
            add( l, BorderLayout.WEST );
            add( tf, BorderLayout.CENTER );
        }
        
        public void addActionListener( ActionListener l ) {
            tf.addActionListener( l );
        }
        
        public Component getEditorComponent() {
            return this;
        }
        
        public Object getItem() {
            return tf.getText();
        }
        
        public void removeActionListener( ActionListener l ) {
            tf.removeActionListener( l );
        }
        
        public void selectAll() {
            tf.selectAll();
        }
        
        public void setItem( Object o ) {
            if ( o != null ) {
                tf.setText( o.toString() );
            }
            else {
                tf.setText( "" );
            }
        }
    }
    
    private class NewComboRenderer extends JLabel implements ListCellRenderer {
        public NewComboRenderer() {
            setOpaque( true );
        }
        
        public Component getListCellRendererComponent(
                JList list, Object value, int index, boolean isSelected, boolean cellHasFocus
        ) {
            setText( value.toString() );
            if ( value instanceof JLabel ) {
                setIcon( ( (JLabel)value ).getIcon() );
            }
            else {
                setIcon( new RedDot() );
            }
            setBackground( isSelected ? Color.red : Color.white );
            setForeground( isSelected ? Color.white : Color.red );
            return this;
        }
    }
    
    private class RedDot implements Icon {
        public int getIconHeight() {
            return 16;
        }
        
        public int getIconWidth() {
            return 16;
        }
        
        public void paintIcon( Component c, Graphics g, int x, int y ) {
            Color old = g.getColor();
            g.setColor( Color.red );
            g.fillOval( x, y, 15, 15 );
            g.setColor( old );
        }
    }
}

-Nate

[Matt Senecal]

Thanks for the great reply! You've been a big help.
---Matt