Java Swing and Thread sleeping

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I decided to make something fun as a break from reading programming books, and I have hit a snag. This is my first swing program, and am ready to wrap it up!

The problem: I clearly don't understand how threads work with Swing. I am writing a GUI for a black jack game, and I did all of the functionality first e.g. drawing a new card to the screen when the player hits, showing the dealer hit after the player decides to stay, etc. This all works.

When I added in the logic to check for a user bust when hitting, or who wins when the user decides to stay, the game instantly goes to the win/loss screen before drawing either: the card the user got that caused a bust, or; the cards that the dealer drew when hitting (if any).

I tried inserting Thread.sleep in various places, to no avail. The program would sleep before drawing the card, then end instantly as above (even though it was placed logically after the call to draw, and before the call to calculate a winner).

also I tried to follow the MVC paradigm here, just fyi.

P.S. my program runs on one thread, I do not explicitly instantiate another, but I vaguely remember reading that Swing spawns it's own thread for graphics stuff

Sorry for that long intro! Here is some code:

The Model class' pertinent methods

    void hit() {
    //run when button is clicked
    player.hand.add(deck.deck.get(0));
    deck.deck.remove(0);
}

boolean isBust() {
    if (player.getScore() > 21)
        return true;

    return false;

}

void dealerHit() {
    while (dealer.getScore() < 17) { //could implement soft 17 rules for more difficulty
        dealer.hand.add(deck.deck.get(0));

        setChanged();
        notifyObservers();
        deck.deck.remove(0);


        //Here was one attempt
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

boolean isWin() {

    //and another
    try {
        TimeUnit.SECONDS.sleep(1);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }

    if ((player.getScore() > dealer.getScore() && player.getScore() <= 21) || dealer.getScore() > 21)
        return true;

    return false;
}

void stay() {
    dealerHit();
    isWin();
}

View Class

void addHitListener(ActionListener HitListener) {
    hit.addActionListener(HitListener);
}

void addStartListener(ActionListener StartListener) {
    start.addActionListener(StartListener);
}

void addStayListener(ActionListener StayListener) {
    stay.addActionListener(StayListener);
}

void display() {
    JFrame myFrame = new JFrame("BlackJack");
    myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    myFrame.setContentPane(this);
    myFrame.setPreferredSize(new Dimension(700,550));

    myFrame.pack();
    myFrame.setVisible(true);
}

void addCards(Player p, Dealer d) {
    topPanel.remove(start);

    pcardPanel.add(playerlabel);
    dcardPanel.add(dealerlabel);        

    for (Card c : p.hand) {
        ImageIcon cc = new ImageIcon(c.img);
        JLabel cC = new JLabel(cc);

        //cC.setAlignmentX(alignmentX); use to get X alignment of card 1 & 2 for splits
        //cC.setAlignmentY(alignmentY); same for Y, then increment by .3f

        pcardPanel.add(cC);


    }

    for (Card c : d.hand)
        dcardPanel.add(new JLabel(new ImageIcon(c.img))); 

    topPanel.add(new JLabel("Options: "));
    topPanel.add(hit);                              
    topPanel.add(stay);                             

    validate();
    repaint();
}

void endGame(boolean isWin) {

    //I think I tried here, too

    removeAll();
    setBackground(new Color(0, 122, 0));

    if (isWin == true)
        add(new JLabel("You won!"));
    else
        add(new JLabel("You Lost"));

    validate();
    repaint();
}

public void hitPlayer(Player p) {
    JLabel hits = new JLabel(new ImageIcon(p.hand.get(p.hand.size()-1).img));
    //hits.setAlignmentY(alignmentY);

    pcardPanel.add(hits);

    validate();
    repaint();
}

public void hitDealer(Dealer d) {
    dcardPanel.add(new JLabel(new ImageIcon(d.hand.get(d.hand.size()-1).img)));
    validate();
    repaint();
}

Controller class:

public class Controller implements Observer {

BlackJack game;
Table t;

Controller(BlackJack game, Table t) {
    this.game = game;
    this.t = t;

    this.game.addObserver(this);
    this.t.addHitListener(new HitListener());
    this.t.addStartListener(new StartListener());
    this.t.addStayListener(new StayListener());

}

public void go() {
    t.display();
}

public void update(Observable obj, Object observed) {
    t.hitDealer(game.getDealer());
}

class HitListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {

        game.hit();

        t.hitPlayer(game.getPlayer());

        if (game.isBust() == true)
            t.endGame(false);

    }
}

class StartListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {
        t.addCards(game.getPlayer(), game.getDealer());
    }
}

class StayListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {
        game.stay();
        //doStay();

        if (game.isWin() == true)
            t.endGame(true);
        else
            t.endGame(false);
    }
}

I just had a thought, since I'm doing this in the actionPerformed methods, could that be why sleep seemed to affect the GUI thread, and not draw the card(s) then sleep. I bet that is it. But I'm going to eat dinner, hopefully someone smarter than myself can lend a hand! Thanks in advance

P.P.S. if there are any typos (I don't think there are) just know that it all compiles and works! And no warnings, if that helps

2

There are 2 answers

0
Michael Bar-Sinai On BEST ANSWER

Swing is indeed a single-thread library, like most UIs. There are also many optimizations to make it work fast. Case in point - most paintings are cached and displayed together. Even if this was not the case, you'd be relying on the speed of the system, which is not a good idea.

If you want a delayed action, you need to use swing's timer (not to be confused with the other timer class). That class has an action listener that goes off when the timer expires. In your case, you'd detect the win/bust condition, start the timer (e.g to fire in 2 seconds) and continue the drawing as usual.

1
Codebender On

This is a little too long for me to read and understand... But I guess your problem is because you are processing everything in the Event Dispatching Thread.

When you paint something on the GUI and then have more processing, the paint will actually reflect on the GUI only when the whole of the thread has finished processing. That's why you are not seeing your drawing before your Thread.sleep method.

Instead you should use SwingWorker to split your processing and GUI updating to different threads.

Look at this https://docs.oracle.com/javase/tutorial/uiswing/concurrency/worker.html