Multiple animations(threads) in a JPanel

Question

I am trying to code a board game in Java.

I have 11 classes including Main. Board class which extends JPanel and draws the board image as well as the dice image. The class Player which extends JCoponent and implements Runnable(Thread). Every player instance is a pawn-animation that it is moving across the board. The player class draws the pawn on the board.

Pattern
How the code it looks like :

Board b=new Board(); 
Player p=new Player();
b.add(p);
JPanel panel=new JPanel();
panel.add(b);
add(panel); //adding the panel to the frame.

The problem is that I can't have more than one pawn simultaneously on the board. I have already tried to re-paint all the players (as non-animation) in another class but it didn't work. I also tried JLayeredPane but maybe I am doing something wrong. Unfortunately, I can't change the above pattern so don't make this suggestion.

Thank you in advance for your help.

P.S: I can't post any code because its huge.
P.P.S: more clarifications will be given, if you ask me.

EDIT: I reform my question. Is it possible to have two animations simultaneously on the same panel? if the answer is a yes ..how I can do that?

Answer 1

It's most likely possible to have many components moving all at once. Either use javax.swing.Timer ou SwingWorker for this to work.

Here is a quick example showing you this. It puts 16 pawns on a board and moves them randomly from one place to another.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestAnimation {

    private static final String PAWN_URL = "http://files.chesskidfiles.com/images_users/tiny_mce/BoundingOwl/bishop_happywhite.png";

    private Image pawn;

    private Map<Location, Pawn> pawnLocations = new HashMap<>();

    private Board board;

    private Timer timer;

    private JLayeredPane glassPane;

    public TestAnimation() {
        try {
            pawn = new ImageIcon(new URL(PAWN_URL)).getImage();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }

    private static class Location {
        public final int row;
        public final int col;

        public Location(int row, int col) {
            super();
            this.row = row;
            this.col = col;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + col;
            result = prime * result + row;
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) {
                return true;
            }
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            Location other = (Location) obj;
            return (col == other.col && row == other.row);
        }
    }

    private static class Cell extends JPanel {

        private final Location location;

        public Cell(Location location) {
            super(new BorderLayout());
            this.location = location;
            setOpaque(true);
            setBackground(((location.row + location.col) % 2) == 0 ? Color.WHITE : Color.BLACK);
        }

        @Override
        protected void addImpl(Component comp, Object constraints, int index) {
            while (getComponentCount() > 0) {
                remove(0);
            }
            super.addImpl(comp, constraints, index);
        }
    }

    private static class Board extends JPanel {

        private Map<Location, Cell> cells = new HashMap<>();

        public Board() {
            super(new GridLayout(8, 8));
            for (int i = 0; i < 8; i++) {
                for (int j = 0; j < 8; j++) {
                    Cell cell = new Cell(new Location(i, j));
                    add(cell);
                    cells.put(new Location(i, j), cell);
                }
            }
        }

        public void add(Pawn pawn, Location location) {
            cells.get(location).add(pawn);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

        public Cell getCell(Location location) {
            return cells.get(location);
        }
    }

    private class Pawn extends JComponent {
        public Pawn() {
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(pawn, 0, 0, getWidth(), getHeight(), this);
        }
    }

    protected void initUI() {
        JFrame frame = new JFrame(TestAnimation.class.getSimpleName());
        board = new Board();
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 2; j++) {
                Location location = new Location(i, j);
                Pawn aPawn = new Pawn();
                board.add(aPawn, location);
                pawnLocations.put(location, aPawn);
            }
        }
        for (int i = 0; i < 8; i++) {
            for (int j = 6; j < 8; j++) {
                Location location = new Location(i, j);
                Pawn aPawn = new Pawn();
                board.add(aPawn, location);
                pawnLocations.put(location, aPawn);
            }
        }
        timer = new Timer(7000, new Animation());
        timer.setInitialDelay(0);
        timer.setRepeats(true);
        timer.setCoalesce(false);
        glassPane = new JLayeredPane();
        glassPane.setOpaque(false);
        frame.add(board);
        frame.setGlassPane(glassPane);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
        timer.start();
        glassPane.setVisible(true);
    }

    public class Animation implements ActionListener {

        private Map<Location, Pawn> futureLocations;

        private Random random = new Random();

        private Timer subTimer;

        private List<Pawn> movingPawns;

        private Map<Pawn, Point> originalCoordinates = new HashMap<>();
        private Map<Pawn, Point> futureCoordinates = new HashMap<>();

        @Override
        public void actionPerformed(ActionEvent e) {
            futureLocations = new HashMap<>();
            movingPawns = new ArrayList<>();
            for (Pawn p : pawnLocations.values()) {
                int row = random.nextInt(8);
                int col = random.nextInt(8);
                Location location;
                while (futureLocations.containsKey((location = new Location(row, col)))) {
                    row = random.nextInt(8);
                    col = random.nextInt(8);
                }
                futureLocations.put(location, p);
                Cell futureCell = board.getCell(location);
                futureCoordinates.put(p, SwingUtilities.convertPoint(futureCell, 0, 0, glassPane));
                movingPawns.add(p);
            }
            for (Pawn p : movingPawns) {
                Point locationInGlassPane = SwingUtilities.convertPoint(p.getParent(), 0, 0, glassPane);
                glassPane.add(p);
                p.setLocation(locationInGlassPane);
                originalCoordinates.put(p, locationInGlassPane);
            }
            subTimer = new Timer(50, new AnimationSteps());
            subTimer.setInitialDelay(0);
            subTimer.setCoalesce(true);
            subTimer.setRepeats(true);
            subTimer.start();
        }

        public class AnimationSteps implements ActionListener {

            private int step = 0;

            @Override
            public void actionPerformed(ActionEvent e1) {
                if (step < 50 + 1) {
                    for (Pawn p : movingPawns) {
                        Point p1 = originalCoordinates.get(p);
                        Point p2 = futureCoordinates.get(p);
                        int x = (int) (p1.x + ((p2.x - p1.x) * (double) step / 50));
                        int y = (int) (p1.y + ((p2.y - p1.y) * (double) step / 50));
                        p.setLocation(x, y);
                    }
                } else {
                    for (Entry<Location, Pawn> e : futureLocations.entrySet()) {
                        board.add(e.getValue(), e.getKey());
                    }
                    board.revalidate();
                    subTimer.stop();
                    pawnLocations = futureLocations;
                }
                step++;

            }

        }
    }

    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException,
            UnsupportedLookAndFeelException {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new TestAnimation().initUI();
            }
        });
    }
}

Answer 2

Maybe your problem is trying to develop a program with a thread for each object, most popular games run with a single thread, two at most. The reason: It will be very complex to synchronize threads with each other, not to mention that your performance will be poor. Even the graphics engine in Java is single threaded and that means you won't have two threads drawing at the same time.