ListCellRenderer with JComboBox

Question

Hi,
I tried to implement a custom ListCellRenderer for a JComboBox:
public class StatusComboBoxRenderer implements ListCellRenderer {
     JLabel label;
     public StatusComboBoxRenderer() {
          super();
          this.label= new JLabel();
     public Component getListCellRendererComponent(
          JList list,
          Object value,
          int index,
          boolean isSelected,
          boolean cellHasFocus) {
          if (value != null){
                         label.setText(((Status)value).getStatus());
          return this.label;
}Now, at first it seems to work. Each entry is displayed correctly. But when I select an entrie, nothing is shown anymore. The functionality still is correct, the entry is selected. But the ComboBox doesn't display the entries anymore.
What could I have done wrong? Should I use something different than a label? It is just Text that is displayed.
And a second problem: I have to test for (value != null). That happens very often. Is this normal or does this seem to be a problem?
Marco

Answer 1

Hello,
i cant reproduce your problems, perhaps something with your Status class ?
If you want your label to show the selection(background) you have to set it opaque.
import javax.swing.*;
import java.awt.*;
public class StatusComboBoxRenderer implements ListCellRenderer {
     JLabel label;
     public StatusComboBoxRenderer() {
          super();
          this.label= new JLabel();
          this.label.setOpaque(true);
     public Component getListCellRendererComponent(
          JList list,
          Object value,
          int index,
          boolean isSelected,
          boolean cellHasFocus) {
          label.setText((String)value);
          if (isSelected) {
               label.setBackground(list.getSelectionBackground());
               label.setForeground(list.getSelectionForeground());
          } else {
               label.setBackground(list.getBackground());
               label.setForeground(list.getForeground());
          return this.label;
     public static void main(String[]args){
          JComboBox box=new JComboBox(new String[]{"A","B","C"});
          box.setRenderer(new StatusComboBoxRenderer());
          JFrame f =new JFrame();
          JPanel p=new JPanel();
          p.add(box);
          f.setBounds(0,0,200,200);
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          f.getContentPane().add(p);
          f.setVisible(true);
}Sun Tutorial: http://java.sun.com/docs/books/tutorial/uiswing/components/combobox.html#renderer
Regards,
Tim