Java Swing Timer Not Working

Question

I am trying to repaint my applet every second in order to show a race between a tortoise and a hare, but the swing timer in my applet doesn't seem to be working properly. Any help or advice would be much appreciated!

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.*;
import javax.swing.*;
import java.awt.Color;

public class Project2 extends Applet
{
int squaret = 1;
int squareh = 1; //initial location of tortoise and hare
int move;
String tmessage;
String hmessage;


Timer timer;

public void init()
{

    timer = new Timer(100, getNewValues); 
    timer.addActionListener(getNewValues);
    timer.start();



}

ActionListener getNewValues = new ActionListener() {

    public void actionPerformed(ActionEvent e) 
    {

        repaint();
    }
};

public void paint (Graphics g) 
{
    move = (int)(Math.random() * 10) + 1;

    if (move > 8)
    {   
        squaret -= 6;
        tmessage = "Tortoise slips!";

        if (squaret < 1)
            squaret = 1;

    }       
    else if (move > 6)
    {
        squaret += 1;
        tmessage = "Tortoise plods slowly along.";
        if (squaret > 49)
            squaret = 50;

        squareh -=2;
        hmessage = "Hare slips slightly.";
        if (squareh < 1)
            squareh = 1;

    }

    else if (move > 5)
    {
        squaret += 1;
        tmessage = "Tortoise plods slowly along.";
        if (squaret > 49)
            squaret = 50;

        squareh -=12;
        hmessage = "Hare makes a big slip.";
        if (squareh < 1)
            squareh = 1;

    }

    else if (move > 2)
    {
        squaret += 3;
        tmessage = "Tortoise plods along quickly.";
        if (squaret > 49)
            squaret = 50;

        squareh += 1;
        hmessage = "Hare makes a small hop.";
        if (squareh > 49)
            squareh = 50;

    }
    else 
    {
        squaret += 3;
        tmessage = "Tortoise plods along quickly.";
        if (squaret > 49)
            squaret = 50;

        squareh += 9;
        hmessage = "Hare makes a big hop.";
        if (squareh > 49)
            squareh = 50;
    }

    g.drawString("Start (Square 1)", 0, 70);
    g.drawString("Finish (Square 50)", 900, 70);


    //determine positions for each area
    //each box is ten wide and 150 tall

    final int WIDTH_OF_OVAL = 4;
    final int HEIGHT_OF_OVAL = 4;
    final int WIDTH_OF_SQUARE = 20;
    final int HEIGHT_OF_SQUARE = 20;
    g.setColor(Color.GREEN);
    g.fillOval(((WIDTH_OF_SQUARE - WIDTH_OF_OVAL) / 2) + WIDTH_OF_SQUARE * (squaret - 1), ((HEIGHT_OF_SQUARE - HEIGHT_OF_OVAL) / 2), WIDTH_OF_OVAL, HEIGHT_OF_OVAL);

    g.setColor(Color.YELLOW);
    g.fillOval(((WIDTH_OF_SQUARE - WIDTH_OF_OVAL) / 2) + WIDTH_OF_SQUARE * (squaret - 1), ((HEIGHT_OF_SQUARE - HEIGHT_OF_OVAL) / 2) + HEIGHT_OF_SQUARE, WIDTH_OF_OVAL, HEIGHT_OF_OVAL);

    //show messages
    g.setColor(Color.BLACK);
    g.drawString(tmessage, 10, 100);
    g.drawString(hmessage, 10, 120);

    g.drawLine(0, HEIGHT_OF_SQUARE, WIDTH_OF_SQUARE * 50, HEIGHT_OF_SQUARE); //draw horizontal middle line

    for (int i = 0; i < 50; i++) //draw vertical lines
    {
        int width = (i + 1) * WIDTH_OF_SQUARE;

        g.drawLine(width, 0, width, HEIGHT_OF_SQUARE * 2);
    }

    if (squaret > 49 && squareh > 49)
    {
        g.drawString("Tie!", 500, 60);
        timer.stop();
    }   
    else if (squaret > 49)
    {
        g.drawString("Turtle wins!", 500, 60);
        timer.stop();
    }
    else if (squareh > 49)
    {
        g.drawString("Hare wins!", 500, 60);
        timer.stop();
    }   
    else
    {

    }   

    update(g);


}

public static void main(String[] args) 
{

    Project2 panel = new Project2();
    JFrame application = new JFrame();

    application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    application.add(panel);
    application.setSize(2600, 300);
    application.setVisible(true);

    }
}

1) Why code an applet? If it is due to spec. by teacher, please refer them to [Why CS teachers should stop teaching Java applets](http://programmers.blogoverflow.com/2013/05/why-cs-teachers-should-stop-teaching-java-applets/). 2) Why AWT rather than Swing? See this answer on [Swing extras over AWT](http://stackoverflow.com/a/6255978/418556) for many good reasons to abandon using AWT components. If you need to support older AWT based APIs, see [Mixing Heavyweight and Lightweight Components](http://www.oracle.com/technetwork/articles/java/mixing-components-433992.html). — Andrew Thompson, Nov 29 '13 at 16:51

tenorsax · Answer 1 · 2013-11-29T16:40:32.940

2

Don't call update() from paint(). update() will eventually trigger paint() and thus you are creating an endless loop of repaints which results in StackOverflowError.

Some other concerns:

Assuming that you want to create an applet I'm not sure what you wanted to achieve with main() method that executes it as a normal application. Also not clear why choose Applet and not JApplet.

See Java Applets for more details and examples. In particular, see Methods for Milestones regarding the main.

edited Nov 29 '13 at 16:40

answered Nov 29 '13 at 16:29

tenorsax

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It works! Thanks so much! For some reason, however, when I run the applet, the animals move together in the race. Do you have any idea why that is? – user3049595 Nov 29 '13 at 16:36
Oh, nevermind. I just made a silly typo in the code. Thanks again for your help! – user3049595 Nov 29 '13 at 16:38

Java Swing Timer Not Working

1 Answers1