How to change attributes of Objects of all windows in a MDI application

Question

Hi,
I have a MDI application to draw Object. In these MDI windows I can modify attributes of Object like color, size... Now I want to create an option, when the user change or modifies attribute of Objects in a window, so it allow to change attributes of objects in all windows. I don't know how I can do it, please help me. Thanks

Answer 1

Allow your objects to alias mutable attribute objects.
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
import java.util.List;
public class Example extends JPanel {
    private List bangles = new ArrayList();
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        for(Iterator j=bangles.iterator(); j.hasNext(); )
            ((Bangle)j.next()).paint(g2);
    public void addBangle(Bangle bangle) {
        bangles.add(bangle);
        repaint();
    public static void main(String[] args) {
        JFrame.setDefaultLookAndFeelDecorated(true);
        JDialog.setDefaultLookAndFeelDecorated(true);
        Example app = new Example();
        JFrame f = new JFrame("Example");
        Container cp = f.getContentPane();
        cp.add(app, BorderLayout.CENTER);
        cp.add(Controller.create(app), BorderLayout.NORTH);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(800,600);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
class Controller {
    private Shade shade1 = new Shade(Color.GREEN), shade2 = new Shade(Color.RED), currentShade=shade1;
    private Example modelView;
    public static JComponent create(Example modelView) {
        return new Controller(modelView).createUI();
    private Controller(final Example modelView) {
        this.modelView = modelView;
        modelView.addMouseListener(new MouseAdapter(){
            public void mousePressed(MouseEvent evt) {
                Rectangle shape = new Rectangle(evt.getX(), evt.getY(), 20, 20);
                modelView.addBangle(new Bangle(shape, currentShade));
    private JComponent createUI() {
        ButtonGroup bg = new ButtonGroup();
        final JToolBar tb = new JToolBar();
        final JRadioButton rb1 = createRadio("Shade 1", true,  shade1, bg, tb);
        final JRadioButton rb2 = createRadio("Shade 2", false, shade2, bg, tb);
        JButton btn = new JButton("Change color of selected shade");
        btn.setContentAreaFilled(false);
        btn.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt) {
                Color newColor = JColorChooser.showDialog(tb, "Choose new color", currentShade.getColor());
                if (newColor != null) {
                    currentShade.setColor(newColor);
                    if (currentShade == shade1)
                        rb1.setForeground(newColor);
                    else
                        rb2.setForeground(newColor);
        tb.add(btn);
        return tb;
    private JRadioButton createRadio(String text, boolean selected, final Shade shade, ButtonGroup bg, JToolBar tb) {
        JRadioButton rb = new JRadioButton(text, selected);
        rb.setContentAreaFilled(false);
        rb.setForeground(shade.getColor());
        rb.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt) {
                currentShade = shade;
        tb.add(rb);
        return rb;
class Bangle {
    private Shape shape;
    private Shade shade;
    public Bangle(Shape shape, Shade shade) {
        this.shape = shape;
        this.shade = shade;
    public void paint(Graphics2D g2) {
        g2.setColor(shade.getColor());
        g2.draw(shape);
class Shade {
    private Color color;
    public Shade(Color color) {
        this.color = color;
    public Color getColor() {
        return color;
    public void setColor(Color color) {
        this.color = color;
}