Need help on Java animation

Some design issues..

You have the following classes: Car, CarThread, CarViewer, CarComponent
In the code above (mine and yours), the implementation is a bit inflexible. I might have some better code later, but let me explain first a better idea.

The CarViewer is the main frame. Next is the CarComponent which can be added to a container to show a number of cars. The CarComponent should have an add method which allows the CarViewer to add cars. Thus the CarComponent holds a list of the Cars in it's component. Now you can choose to have every Car in a single thread or every CarComponent in a single thread. I think the later is preferable, since it's more scalable and less intensive. The Car class should only be concerned with drawing itself and keeping the position and the CarThread should only be concerned with the regular interval movement of the cars.

So in Java terms it should look like:

==CarViewer==
public static void main(String[] args);

==CarComponent==
private LinkedList<Car> cars;
private CarThread animation;

public void addCar(Car car);
public void removeCar(Car car);
public void startAnimation();
public void stopAnimation();

==Car==
private int x;
private int y;
private int width;
private int height;

public void move(int dx, int dy);

==CarThread==
public CarThread(LinkedList<Car> cars);
public void run();

Sth. like this.. I will start coding now, let me see if I can make some nice setup.

Mark

Thank you so much for that, Mark. You deserve my 350 points :)

Mark, if you have anything more to add, email me:

Dragon_316ca@yahoo.ca

Do you still want the code for the design i suggested?

Mark

Yeah sure.

Here the code:

===CarViewer===
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JFrame;

//Class is the visible frame. For now only
//consisting of a CarComponent and some buttons
//to start and stop animation.
class CarViewer extends JFrame implements ActionListener
{
    private final static int FRAME_WIDTH = 800;
    private final static int FRAME_HEIGHT = 400;

    private CarComponent carComponent;

    private JButton butStart;
    private JButton butStop;

    //Constructor
    public CarViewer()
    {
        //Frame properties
        this.setSize(FRAME_WIDTH, FRAME_HEIGHT);
        this.setTitle("Cars Example");
        this.setLayout(new BorderLayout());
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add CarComponent
        this.carComponent = new CarComponent();
        this.add(this.carComponent, BorderLayout.CENTER);

        //Add some cars
        this.carComponent.addCar(new Car(10, 10));
        this.carComponent.addCar(new Car(10, Car.HEIGHT+20));
        this.carComponent.addCar(new Car(10, Car.HEIGHT*2+30));
        this.carComponent.addCar(new Car(10, Car.HEIGHT*3+40));
        this.carComponent.addCar(new Car(10, Car.HEIGHT*4+50));
        this.carComponent.addCar(new Car(10, Car.HEIGHT*5+60));

        //Add buttons
        this.butStart = new JButton("Start");
        this.butStart.addActionListener(this);
        this.butStart.setActionCommand("start");
        this.butStop = new JButton("Stop");
        this.butStop.addActionListener(this);
        this.butStop.setActionCommand("stop");
        this.butStop.setEnabled(false);

        JPanel pnlButtons = new JPanel();
        pnlButtons.add(this.butStart);
        pnlButtons.add(this.butStop);
        this.add(pnlButtons, BorderLayout.NORTH);
    }

    //Handle actions
    public void actionPerformed(ActionEvent ae)
    {
        if("start".equals(ae.getActionCommand()))
        {
            this.butStop.setEnabled(true);
            this.butStart.setEnabled(false);

            this.carComponent.startAnimation();
        }
        else if("stop".equals(ae.getActionCommand()))
        {
            this.butStart.setEnabled(true);
            this.butStop.setEnabled(false);

            this.carComponent.stopAnimation();
        }
    }

    //Program entry
    public static void main(String[] args)
    {
        CarViewer carViewer = new CarViewer();
        carViewer.setVisible(true);
    }
}
===CarComponent===
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;
import java.util.LinkedList;

//Class for holding a number of cars. All tasks
//are delegated to the objects. This component
//starts and stops the CarThread.
class CarComponent extends JComponent
{
    private LinkedList<Car> cars;
    private CarThread carThread;

    //Constructor
    public CarComponent()
    {
        this.cars = new LinkedList<Car>();
        this.carThread = new CarThread(this);
    }

    //Paint component
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;

        //Loop cars
        for(Car car : this.cars)
            car.draw(g2);
    }

    //Add car to list
    public void addCar(Car car)
    {
        this.cars.add(car);
    }

    //Remove car from list
    public void removeCar(Car car)
    {
        this.cars.remove(car);
    }

    //Returns list of cars
    public LinkedList<Car> getCars()
    {
        return this.cars;
    }

    //Start animation
    public void startAnimation()
    {
        this.carThread.startAnimation();
    }

    //Stop animation
    public void stopAnimation()
    {
        this.carThread.stopAnimation();
    }
}
===CarThread===
import java.util.LinkedList;

//Class is only concerned with moving the cars on
//a specific interval.
class CarThread implements Runnable
{
    private final static int INTERVAL = 60;

    private CarComponent carComponent;
    private boolean running;

    //Constructor
    public CarThread(CarComponent carComponent)
    {
        this.carComponent = carComponent;
        this.running = false;
    }

    //Thread loop
    public void run()
    {
        this.running = true;
        while(running)
        {
            try
            {
                //Move cars
                for(Car car : this.carComponent.getCars())
                {
                    car.move(5, 0);
                }

                //Repaint
                this.carComponent.repaint();

                //Sleep for INTERVAL ms
                Thread.sleep(INTERVAL);
            }
            catch (InterruptedException ie)
            {
                System.out.println("Interrupt exception. Animation will stop now.");
                this.running = false;
            }
        }
    }

    //Start thread
    public void startAnimation()
    {
        if(!this.running)
            new Thread(this).start();
    }

    //Stop thread
    public void stopAnimation()
    {
        this.running = false;
    }
}
===Car===
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;

//Class is only concerned with drawing the car.
class Car
{
    public final static int WIDTH = 120;
    public final static int HEIGHT = 70;

    private int x;
    private int y;

    //Constructor
    public Car(int x, int y)
    {
        this.x = x;
        this.y = y;
    }

    //Draw car
    public void draw(Graphics2D g2)
    {
        Rectangle body = new Rectangle(this.x, this.y, 120, 10);
        Rectangle window = new Rectangle(this.x + 30, this.y - 50, 15, 15);

        Ellipse2D.Double frontTire = new Ellipse2D.Double(this.x + 10, this.y + 10, 20, 20);
        Ellipse2D.Double rearTire = new Ellipse2D.Double(this.x + 85, this.y + 10, 20, 20);

        Point2D.Double r1 = new Point2D.Double(this.x, this.y - 35);
        Point2D.Double r2 = new Point2D.Double(this.x, this.y);
        Point2D.Double r3 = new Point2D.Double(this.x + 50, this.y);
        Point2D.Double r4 = new Point2D.Double(this.x + 50, this.y + 10);
        Point2D.Double r5 = new Point2D.Double(this.x + 35, this.y - 60);
        Point2D.Double r6 = new Point2D.Double(this.x + 50, this.y - 60);
        Point2D.Double r7 = new Point2D.Double(this.x + 50, this.y);

        Line2D.Double frontWindshield = new Line2D.Double(r1, r2);
        Line2D.Double roofTop = new Line2D.Double(r5, r6);
        Line2D.Double rearWindshield = new Line2D.Double(r6, r7);
        Line2D.Double anotherFront = new Line2D.Double(r1, r5);

        g2.draw(body);
        g2.draw(window);
        g2.draw(frontTire);
        g2.draw(rearTire);
        g2.draw(frontWindshield);
        g2.draw(roofTop);
        g2.draw(rearWindshield);
        g2.draw(anotherFront);
    }

    //Move car
    public void move(int dx, int dy)
    {
        this.x += dx;
        this.y += dy;
    }
}

I did not change the drawing of the car, so now they ride backwards, but it shouldn't be difficult to adjust now. This is a pretty flexible design if you ask me. I am pretty proud at this piece of code, if I might say so myself. :-)

Have fun.
Mark

How can you make the truck to move "in reverse"? Please tell me via email: Dragon_316ca@yahoo.ca

thanks

Use negative numbers for the move(int dx, int dy) method.

I believe it is not allowed to sent email if the question is posted on this forum.. since you would get questions without answers, being answered. :-)

Mark