JFrame Isn't Closable Despite frame.setDefaultCloseOperation()

Question

I am having a problem where the panel doesn't load in the JFrame and the JFrame itself doesn't set the default close operation, but performs setSize() and setVisible(). I have tried running the frame initialization in main, in the run() method, and in the frame's constructor and there is no difference. The MouseListeners don't seem to be functional, but there's no way to know for sure without the panel being added to the frame, which it isn't. My main goals of posting this question are to get the Frame to close when you click on the x, and to get the panel to be added to the frame again. I'm certain it is not a problem in gameState.buffer() or gameStae.paint(g). It's for a video game called When Pigs Fly. Here is the code:

Main class:

package when.pigs.fly;

public class Main {
    static Frame frame;
    public static void main(String[] args) {
        frame=new Frame();
        frame.panel.run();
    }
}

Frame class:

package when.pigs.fly;

import javax.swing.JFrame;

public class Frame extends JFrame{
    Panel panel;
    int windowWidth,windowHeight;
    public Frame(){
        super("When Pigs Fly");
        
        panel=new Panel();
        panel.setListeners();
        
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(1000,600);
        buffer();
        
        add(panel);
        setVisible(true);
    }
    
    public final void buffer(){
        windowWidth=getContentPane().getWidth();
        windowHeight=getContentPane().getHeight();
    }
}

Panel class:

package when.pigs.fly;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JPanel;
import static when.pigs.fly.GameState.gameState;
import static when.pigs.fly.Main.frame;

public class Panel extends JPanel implements MouseListener,MouseMotionListener{
    private long timeElapsed;
    int mouseX,mouseY;
    boolean mouseDown;
    
    public Panel(){
        gameState=new GameState(1);
    }
    
    public final void setListeners(){
        addMouseListener(this);
        addMouseMotionListener(this);
    }
    
    public void run(){
        boolean run=true;
        while(run){
            long timeAtStart=System.nanoTime();
            
            if(timeElapsed>=33333333){
                gameState.buffer();
                frame.buffer();
                timeElapsed-=33333333;
            }
            repaint();
            
            timeElapsed+=System.nanoTime()-timeAtStart;
        }
    }
    
    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        gameState.paint((Graphics2D)g);
    }
    
    @Override
    public void mouseClicked(MouseEvent me) {
        
    }

    @Override
    public void mousePressed(MouseEvent me) {
        mouseDown=true;
    }

    @Override
    public void mouseReleased(MouseEvent me) {
        mouseDown=false;
    }

    @Override
    public void mouseEntered(MouseEvent me) {}

    @Override
    public void mouseExited(MouseEvent me) {}

    @Override
    public void mouseDragged(MouseEvent me) {
        mouseX=me.getX();
        mouseY=me.getY();
    }

    @Override
    public void mouseMoved(MouseEvent me) {
        mouseX=me.getX();
        mouseY=me.getY();
    }

}

Answer 1

Suspicion abounds, but I suspect, based on your description, your run method is blocking the Event Dispatching Thread.

Swing is single thread and NOT thread safe. This means that you should not run long running or blocking code with in the context of the Event Dispatching Thread and you shouldn't update the UI or any state the UI relies on out side of the Event Dispatching Thread.

See Concurrency in Swing for more details.

A simple solution would be to use a Swing Timer, for example...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Timer timer;
        private int mouseX, mouseY;
        private boolean mouseDown;

        public TestPane() {
            MouseHandler handler = new MouseHandler();
            addMouseListener(handler);
            addMouseMotionListener(handler);
        }

        protected void start() {
            if (timer != null) {
                return;
            }
            timer = new Timer(5, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    // Check input
                    // Update game state
                    repaint();
                }
            });
            timer.start();
        }

        protected void stop() {
            if (timer == null) {
                return;
            }
            timer.stop();
            timer = null;
        }

        @Override
        public void addNotify() {
            super.addNotify();
            start();
        }

        @Override
        public void removeNotify() {
            super.removeNotify();
            stop();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(1000, 600);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int dotSize = 6;
            if (mouseDown) {
                g2d.setColor(Color.RED);
                g2d.fillOval(mouseX - dotSize, mouseY - dotSize, dotSize * 2, dotSize * 2);
            } else {
                g2d.setColor(Color.BLACK);
                g2d.drawOval(mouseX - dotSize, mouseY - dotSize, dotSize * 2, dotSize * 2);
            }
            g2d.dispose();
        }

        protected class MouseHandler extends MouseAdapter {

            @Override
            public void mousePressed(MouseEvent me) {
                mouseDown = true;
            }

            @Override
            public void mouseReleased(MouseEvent me) {
                mouseDown = false;
            }

            @Override
            public void mouseDragged(MouseEvent me) {
                mouseX = me.getX();
                mouseY = me.getY();
            }

            @Override
            public void mouseMoved(MouseEvent me) {
                mouseX = me.getX();
                mouseY = me.getY();
            }
        }

    }
}