Question

The following is the condensed code of my applet game:

import java.applet.Applet;
import java.awt.event.*;
import java.awt.*;

public class Game extends Applet implements KeyListener, Runnable {
    Button options = new Button("Options");
    Thread thread = new Thread(this);

    public void init() {
        addKeyListener(this);
        thread.start();
    }

    public void paint(Graphics graphics) {
        // draw stuff
    }

    public void run() {
        try {
            while (true) {
                thread.sleep(40);
                repaint();
            }
        } catch (InterruptedException exception) {}
    }

    public void keyPressed(KeyEvent keyEvent) {
        switch (keyEvent.getKeyCode()) {
        case KeyEvent.VK_ESCAPE:
            // pause game
            add(options);
        }
    }

    public void keyReleased(KeyEvent keyEvent) {}
    public void keyTyped(KeyEvent keyEvent) {}
}

My game runs as it’s expected to. However when the user presses Esc I want to pause the game and display an options button.

The problem is that when I press Esc it pauses the game as expected. However it doesn’t display the button on the screen. I’ve tried to search for a solution to no avail. What exactly is happening?

Answer 1

Works perfectly fine for me…

public class TestApplet02 extends Applet implements KeyListener, Runnable {

    Button options = new Button("Options");
    Thread thread = new Thread(this);
    int y = 0;

    public void init() {
        thread.start();
    }

    @Override
    public void start() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                setLayout(new BorderLayout());
                addKeyListener(TestApplet02.this);
            }
        });
    }

    public void paint(Graphics graphics) {
        super.paint(graphics);
        Graphics2D g2d = (Graphics2D) graphics;
        y++;
        if (y > getHeight()) {
            y = 0;
        }
        g2d.drawLine(0, y, getWidth(), y);
    }

    public void run() {
        try {
            while (true) {
                thread.sleep(40);
                SwingUtilities.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        repaint();
                    }
                });
            }
        } catch (InterruptedException exception) {
        }
    }

    public void keyPressed(KeyEvent keyEvent) {
        switch (keyEvent.getKeyCode()) {
            case KeyEvent.VK_ESCAPE:
                // pause game
                add(options);
                invalidate();
                revalidate();
        }
    }

    public void keyReleased(KeyEvent keyEvent) {
    }

    public void keyTyped(KeyEvent keyEvent) {
    }
}

From the link TrashGod provided…

In an applet, the GUI-creation task must be launched from the init
method using invokeAndWait; otherwise, init may return before the GUI
is created, which may cause problems for a web browser launching an
applet. In any other kind of program, scheduling the GUI-creation task
is usually the last thing the initial thread does, so it doesn’t
matter whether it uses invokeLater or invokeAndWait.

UPDATED

The major issues I had were:

In you’re escape key handler, if direction is 0, the pause option will never activate…

case KeyEvent.VK_ESCAPE:
    direction = -direction;

    if (direction < 0) {
        add(options);
    } else {
        remove(options);
    }

The other thing I had to was call revalidate…

invalidate();
revalidate();
repaint();