animation not animating...

[Karen Nelson]

Hi,
I am trying to do a simple animation (like in HeadStart java p 384) but the panel is not redrawing. Here is the code bit:

 for(int i=1; i<=160; ++i) {
addKid();
graphPanel.repaint();
try { Thread.sleep(50); }
catch(Exception ex) {}
}
 

This code is attached to a button listener, and if I change the limit of hte loop to 1 and click the button repeatedly, everything looks fine (animated, that is). But when I do 160 steps, only the last step gets drawn (after a long pause for all the sleeps).

Any help would be greatly appreciated!
-Karen.

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import javax.swing.*;
 
public class AnimationTest extends JPanel implements ActionListener
{
    Ellipse2D.Double ball;
    int dx;
    int dy;
    BallMover mover;
 
    public AnimationTest()
    {
        ball = new Ellipse2D.Double(50, 50, 20, 20);
        dx = 3;
        dy = 2;
        mover = new BallMover(this);
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 =(Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        g2.setPaint(Color.red);
        g2.fill(ball);
    }
 
    public void advance()
    {
        checkBoundries();
        ball.x += dx;
        ball.y += dy;
        repaint();
    }
 
    private void checkBoundries()
    {
        if(ball.x + dx < 0 || ball.x + ball.width + dx > getWidth())
            dx *=-1;
        if(ball.y + dy < 0 || ball.y + ball.height + dy > getHeight())
            dy *= -1;
    }
 
    public static void main(String[] args)
    {
        AnimationTest test = new AnimationTest();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test.getUIPanel(), "North");
        f.getContentPane().add(test);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    public void actionPerformed(ActionEvent e)
    {
        JButton button = (JButton)e.getSource();
        String ac = button.getActionCommand();
        if(ac.equals("thread"))
            mover.start();
        if(ac.equals("modified"))
        {
            Thread thread = new Thread(new Runnable()
            {
                public void run()
                {
                    for(int i=1; i<=160; ++i) {
                        advance();
                        repaint();
                        try {
                            Thread.sleep(50);
                        } catch(Exception ex) {
                            System.out.println("hello world");
                        }
                    }
                }
            });
            thread.setPriority(Thread.NORM_PRIORITY);
            thread.start();
        }
    }
 
    private JPanel getUIPanel()
    {
        JButton modified = new JButton("modified");
        JButton thread = new JButton("thread");
        modified.setActionCommand("modified");
        thread.setActionCommand("thread");
        modified.addActionListener(this);
        thread.addActionListener(this);
        JPanel panel = new JPanel();
        panel.add(modified);
        panel.add(thread);
        return panel;
    }
}
 
class BallMover implements Runnable
{
    AnimationTest testPanel;
    Thread thread;
    int count;
 
    public BallMover(AnimationTest at)
    {
        testPanel = at;
    }
 
    public void start()
    {
        count = 0;
        thread = new Thread(this);
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
    }
 
    public void run()
    {
        while(count++ < 160)
        {
            try
            {
                Thread.sleep(50);
            }
            catch(InterruptedException ie)
            {
                System.err.println("interrupt: " + ie.getMessage());
                break;
            }
            testPanel.advance();
        }
    }
}