Question

At the outset: I know that what I am doing is bad design. I am trying this to get a better feel of Java – what is possible, what is not and why?

I have written the following code:

    import java.awt.*;
    import java.awt.event.*;

    import javax.swing.*;

    public class ButtonTest
    {
        public static void main(String[] args)
        {
            EventQueue.invokeLater(new Runnable()
            {
                @Override
                public void run()
                {
                    ButtonFrame frame = new ButtonFrame();
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setVisible(true);
                }
            });
        }
    }

    @SuppressWarnings("serial")
    class ButtonFrame extends JFrame
    {
        private final static int DEFAULT_WIDTH = 300;
        private final static int DEFAULT_HEIGHT = 200;
        private final JPanel buttonPanel;

        public ButtonFrame()
        {
            this.setTitle("Button Frame");
            this.setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

            PanelButton yellowButton = new PanelButton("Yellow", Color.YELLOW, this);
            PanelButton redButton = new PanelButton("Red", Color.RED, this);
            PanelButton blueButton = new PanelButton("Blue", Color.BLUE, this);

            this.buttonPanel = new JPanel();
            this.buttonPanel.add(yellowButton);
            this.buttonPanel.add(redButton);
            this.buttonPanel.add(blueButton);

            // add panel to frame
            this.add(this.buttonPanel);
        }
    }

    @SuppressWarnings("serial")
    class PanelButton extends JButton implements ActionListener
    {
        private final Color buttonColor;
        private final ButtonFrame containingFrame;

        public PanelButton(String title, Color buttonColor,
                ButtonFrame containingFrame)
        {
            super(title);
            this.buttonColor = buttonColor;
            this.containingFrame = containingFrame;
            this.addActionListener(this);
        }

        @Override
        public void actionPerformed(ActionEvent event)
        {
            this.containingFrame.setBackground(this.buttonColor);
        }
    }

But this is not working. I see from the debugger that actionPerformed() is being invoked and it has the expected values. I am not able to understand what is happening here. Can someone please help me?

Answer 1

You can skip passing the container and just do

@Override
public void actionPerformed(ActionEvent event)
{
    this.getParent().setBackground(buttonColor);
}