painting a particular button from a grid of buttons

Question

The following grid of buttons is defined as :

JButton button_x = new RoundButton();

Answer 1

The problem is the reliance on the GameState, ALL your round buttons use the same logic to paint themselves, that is, when the game is completed, they will all be painted WHITE

Instead, you should rely on the properties of the button. Set it up so that the colors are actually derived from the button itself.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class BadButton01 {

    public static void main(String[] args) {
        new BadButton01();
    }

    public BadButton01() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public static class GameState {

        private static boolean isComplete;

        public static boolean getIfComplete() {
            return isComplete;
        }

        public static void setComplete(boolean value) {
            isComplete = value;
        }

    }

    public class TestPane extends JPanel {

        private RoundButton[] btns = new RoundButton[]
        {
            new RoundButton("1"),
            new RoundButton("2"),
            new RoundButton("3"),
            new RoundButton("4"),
            new RoundButton("5"),
            new RoundButton("6"),
            new RoundButton("7"),
            new RoundButton("8"),
            new RoundButton("9")
        };

        public TestPane() {
            setLayout(new GridLayout(3, 3));
            for (RoundButton btn : btns) {
                add(btn);
            }
            btns[0].addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    GameState.setComplete(true);
                    btns[0].setBackground(Color.WHITE);
                    btns[1].setBackground(Color.WHITE);
                    btns[2].setBackground(Color.WHITE);
                    repaint();
                }
            });
        }

    }

    public class RoundButton extends JButton {

        public RoundButton(String label) {
            super(label);
            this.setContentAreaFilled(false);
            setBorderPainted(false);
            setFocusPainted(false);
            setOpaque(false);
            Dimension size = this.getPreferredSize();
            size.height = size.width = Math.max(size.height, size.width);
            this.setPreferredSize(size);
            setBackground(Color.GREEN);
        }

        @Override
        protected void paintComponent(Graphics g) {
//            if (!GameState.getIfComplete()) { // If the game is not complete or has just started
//                this.setBorder(null);
//                g.setColor(Color.BLACK);
//                g.fillRect(0, 0, this.getSize().width, this.getSize().height);
                if (this.getModel().isArmed()) {
                    g.setColor(Color.RED);
                } else {
//                    g.setColor(Color.GREEN);
                    g.setColor(getBackground());
                }
//            } else {
//                this.setBorder(null);
//                g.setColor(Color.BLACK);
//                g.fillRect(0, 0, this.getSize().width, this.getSize().height);
//                g.setColor(Color.WHITE);
//                g.fillOval(0, 0, this.getSize().width - 1, this.getSize().height - 1);
//                g.setColor(getBackground());
//            }
            g.fillOval(0, 0, this.getSize().width - 1, this.getSize().height - 1);
            super.paintComponent(g);
        }

    }

}