Change Preview Panel for JColorChooser

Question

The objective is to change the Preview section from this :

To something like this where the Preview area has a border, a solid box in the background and "Hello World" string which changes to the color selected for the Preview.

Started with this sample from java2 which simply shows the JColorChooser.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JColorChooser;
import javax.swing.JFrame;

public class ColorChooserSample {
  public static void main(String args[]) {
    JFrame f = new JFrame("JColorChooser Sample");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container content = f.getContentPane();
    final JButton button = new JButton("Pick to Change Background");

    ActionListener actionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        Color initialBackground = button.getBackground();
        JColorChooser jColorChooser = new JColorChooser();
        jColorChooser.setPreviewPanel(null);
        Color background = jColorChooser.showDialog(null,
            "JColorChooser Sample", initialBackground);
        if (background != null) {
          button.setBackground(background);
        }
      }
    };
    button.addActionListener(actionListener);
    content.add(button, BorderLayout.CENTER);
    f.setSize(300, 200);
    f.setVisible(true);
  }
}

Just to see if I can even affect the Preview area, I modified the original code from this :

    Color background = JColorChooser.showDialog(null,
        "JColorChooser Sample", initialBackground);

To this :

        JColorChooser jColorChooser = new JColorChooser();
        jColorChooser.setPreviewPanel(null);
        Color background = jColorChooser.showDialog(null,
            "JColorChooser Sample", initialBackground);

Basically this is to attempt to see if the Preview section could be null (blank) but it had no affect which has me wondering if the setPreviewPanel() is the correct call.

Also, after the code change this Warning appears : The static method showDialog(Component, String, Color) from the type JColorChooser should be accessed in a static way

Questions :

Are there any examples which alter the preview section of the Color Chooser?

Why did the null above not work.

If the Warning indicates that JColorChooser should be accessed in a static way, how would one actually make a setPreviewPanel() call?

Answer 1

There weren't many examples of modifying the JColorChooser preview panel. I found four examples. Along with the Javadoc for JColorChooser, I created a working example of a modified JColorChooser preview panel.

I modified the original JFrame / JPanel to change the background color of the JPanel, so it would be easier to see the result.

Here's the modified JColorChooser.

Here I changed the background color of the preview JPanel to yellow.

Which then changes the background color of the main JPanel to yellow.

Here's the code. I separated the code into bite-sized methods and classes, so I could concentrate on one part of the GUI data a time.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JColorChooser;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class ColorChooserSample implements Runnable{

    public static void main(String args[]) {
        SwingUtilities.invokeLater(
                new ColorChooserSample());
    }

    private JPanel panel;

    @Override
    public void run() {
        JFrame frame = new JFrame(
                "JColorChooser Sample");
        frame.setDefaultCloseOperation(
                JFrame.EXIT_ON_CLOSE);

        panel = new JPanel();
        panel.setPreferredSize(new Dimension(300, 200));
        JButton button = new JButton(
                "Pick to Change JPanel Background");
        button.addActionListener(new ColorListener());
        panel.add(button);

        frame.add(panel, BorderLayout.CENTER);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public void setJPanelBackground(Color color) {
        panel.setBackground(color);
        panel.repaint();
    }

    public class ColorListener implements 
            ActionListener, ChangeListener {

        private JColorChooser chooser;

        private JPanel previewPanel;

        @Override
        public void actionPerformed(
                ActionEvent actionEvent) {
            Color backgroundColor = showDialog(panel, 
                    "Set JPanel Background", 
                    panel.getBackground());
            setJPanelBackground(backgroundColor);
        }

        private Color showDialog(Component component, 
                String title, Color initialColor) 
                        throws HeadlessException {
            chooser = new JColorChooser(initialColor);
            chooser.getSelectionModel()
                .addChangeListener(this);

            // configuring color chooser panel
            previewPanel = new JPanel();
            previewPanel.setBackground(initialColor);
            JLabel label = new JLabel("Hello World!");
            previewPanel.add(label);
            chooser.setPreviewPanel(previewPanel);

            // creating dialog
            ColorTracker ok = new ColorTracker(chooser);
            JDialog dialog = JColorChooser.createDialog(
                    component, title, true, chooser, 
                    ok, null);
            dialog.setVisible(true);
            return ok.getColor();
        }

        @Override
        public void stateChanged(ChangeEvent event) {
            Color newColor = chooser.getColor();
            previewPanel.setBackground(newColor);
        }

    }

    private class ColorTracker implements ActionListener {

        private Color color;

        private JColorChooser chooser;

        public ColorTracker(JColorChooser chooser) {
            this.chooser = chooser;
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            color = chooser.getColor();
        }

        public Color getColor() {
            return color;
        }

    }

}