Using a custom renderer for JComboBox

[Biliang Zhou]

Nice Friday, guys (a little chilly though...).

I have successfully created a custom renderer for a JComboBox (to change the background color of the pull-down menu, so this color agrees with the background color of the JPanel that is holding the JComboBox, which has been changed to light blue).

But I still have two problems:

First, the combobox lost the mouseover effect - the default renderer works like if you bring up the pulldown menu, and mouseover any item, that item will be highlighted. With my custom renderer, this effect is gone...

Second, is it possible to create a gradient effect on the JComboBox? Like the up-to-down or left-to-right gradient. I wonder whether I need a different look and feel scheme to achieve this...


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
package test;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;

import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class TestCustomRenderer extends JPanel{

JComboBox comboBox;

public TestCustomRenderer()
{
super(new BorderLayout());
this.setPreferredSize(new Dimension(200, 100));
this.add(get_comboBox(), BorderLayout.SOUTH);
this.setBackground(new Color(153, 204, 255));
}

private JComboBox get_comboBox()
{
comboBox = new JComboBox();
comboBox.addItem("Planning");
comboBox.addItem("Testing");
comboBox.setBackground(new Color(153, 204, 255));
ComboBoxRenderer renderer = new ComboBoxRenderer();
comboBox.setPreferredSize(new Dimension(80, 25));
comboBox.setRenderer(renderer);
return comboBox;
}

private static void createAndShowGUI()
{
JFrame frame = new JFrame("TestCustomRenderer");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JComponent newContentPane = new TestCustomRenderer();
newContentPane.setOpaque(true);
frame.setContentPane(newContentPane);

frame.pack();
frame.setVisible(true);
}

public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}

class ComboBoxRenderer extends BasicComboBoxRenderer
{
public ComboBoxRenderer() {
super();
setOpaque(true);
}

public Component getListCellRendererComponent(
JList list,
Object value,
int index,
boolean isSelected,
boolean cellHasFocus) {
setText(value.toString());
if(cellHasFocus)
{
setText("value");
}
else
{
setBackground(new Color(153, 204, 255));
}
return this;
}
}
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[ November 03, 2006: Message edited by: Biliang Zhou ]

[Michael Dunn]

try this for the combo backgrounds

    
import java.awt.*;
import javax.swing.*;
class TestCustomRenderer extends JPanel
{
  static Color oldColor;//<--------------
  JComboBox comboBox;
  public TestCustomRenderer()
  {
    super(new BorderLayout());
    this.setPreferredSize(new Dimension(200, 100));
    this.add(get_comboBox(), BorderLayout.SOUTH);
    this.setBackground(new Color(153, 204, 255));
  }
  private JComboBox get_comboBox()
  {
    comboBox = new JComboBox();
    comboBox.addItem("Planning");
    comboBox.addItem("Testing");
    ComboBoxRenderer renderer = new ComboBoxRenderer();
    comboBox.setPreferredSize(new Dimension(80, 25));
    comboBox.setRenderer(renderer);
    comboBox.setBackground(new Color(153, 204, 255));//<---for the button
    return comboBox;
  }
  private static void createAndShowGUI()
  {
    JFrame frame = new JFrame("TestCustomRenderer");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JComponent newContentPane = new TestCustomRenderer();
    newContentPane.setOpaque(true);
    frame.setContentPane(newContentPane);
    frame.pack();
    frame.setVisible(true);
  }
  public static void main(String[] args)
  {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        oldColor = UIManager.getColor("ComboBox.selectionBackground");//<---------------
        UIManager.put("ComboBox.selectionBackground",new javax.swing.plaf.ColorUIResource(new Color(153, 204, 255)));//<-----
        createAndShowGUI();
      }
    });
  }
  class ComboBoxRenderer extends javax.swing.plaf.basic.BasicComboBoxRenderer
  {
    public ComboBoxRenderer()
    {
      super();
      setOpaque(true);
    }
    public Component getListCellRendererComponent(JList list,Object value,int index,boolean isSelected,boolean cellHasFocus)
    {
      setText(value.toString());
      if(isSelected) setBackground(oldColor);
      else setBackground(new Color(153, 204, 255));
      return this;
    }
  }
}

here's a gradient button (not sure where this came from)

    
import javax.swing.*;
import java.awt.*;
class Testing extends JFrame
{
  public Testing()
  {
    setSize(150,100);
    setLocation(400,300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    JPanel panel = new JPanel();
    JButton button = new JButton("OK");
    JButton searchButton = new JButton("Search"){
      public void paintComponent(Graphics g)
      {
        setOpaque(false);
        Graphics2D g2d = (Graphics2D) g;
        Paint oldPaint = g2d.getPaint();
        Paint newPaint = new GradientPaint(0,0,Color.blue,0,15,Color.white,true);
        g2d.setPaint(newPaint);
        g2d.fillRect(0,0,getWidth(),getHeight());
        g2d.setPaint(oldPaint);
        super.paintComponent(g);
      }};
    searchButton.setContentAreaFilled(false);
    panel.add(button);
    panel.add(searchButton);
    getContentPane().add(panel);
  }
  public static void main(String[] args){new Testing().setVisible(true);}
}

[Biliang Zhou]

Thank you, Michael!

Now I can use the recursive algorithm you showed me yesterday to traverse through all the comboboxes and give them different background colors.

And the GradientPaint example is just easy to follow - basically we can use the GradientPaint(x1,y1,Color.blue,x2,y2,Color.white,true) to generate color patterns. It all depends the setting of the coordinates how the color pattern is going to "gradiate".