Displaying images on a JPanel from another thread

Question

Hello all,
I'm trying to write my first multithreaded program. I have a program with 2 threads. The first (ie main) thread sets up a gui and performs some calculations, and the second thread changes the background of the gui at intervals. I been having a couple of problems with loading images in the second thread.
In my main thread, I initialise and make runnable the second thread, which is the thread that changes the gui background:
ThreadChangeBackground myThread = new ThreadChangeBackground(graphicPanel);
new Thread(myThread).start(); I have tested the threads and they are working fine.
The problem is when I try to load images and show them. I've never worked with images before, so I don't know what the best way of loading them onto a GUI is.
This is the code for the second thread:
package Graphics;
import java.awt.*;
import javax.swing.*;
import java.awt.Container.*;
import java.awt.Toolkit.*;
public class ThreadChangeBackground implements Runnable
    JPanel changeable; //changeable = graphicPanel
    Image bgImage1;
    Image bgImage2;
    Image bgImage3;
    Image bgImage4;
    Image bgImage5;
    Image bgImage6;
    Image bgImage7;
    Image bgImage8;
    Image bgImage9;
    Image bgImage10;
    public ThreadChangeBackground(JPanel changeable)
        this.changeable = changeable;
    public void run()
        try
            bgImage1 = Toolkit.getDefaultToolkit().getImage("1");
            bgImage2 = Toolkit.getDefaultToolkit().getImage("2");
            bgImage3 = Toolkit.getDefaultToolkit().getImage("3");
            bgImage4 = Toolkit.getDefaultToolkit().getImage("4");
            bgImage5 = Toolkit.getDefaultToolkit().getImage("5");
            bgImage6 = Toolkit.getDefaultToolkit().getImage("6");
            bgImage7 = Toolkit.getDefaultToolkit().getImage("7");
            bgImage8 = Toolkit.getDefaultToolkit().getImage("8");
            bgImage9 = Toolkit.getDefaultToolkit().getImage("9");
            bgImage10 = Toolkit.getDefaultToolkit().getImage("10");
            //run this thread process 200 times
            for (int i = 1; i <= 200; i++)
                //load a new image every 3 seconds
                for (int imageCount = 1; imageCount <= 10; imageCount++)
                    loadImage(imageCount);
                    Thread.sleep(3000);
        catch (Exception e) {}
//the problem is here 
    private void loadImage(int imageNo)
        Graphics g = changeable.getGraphics();
        g.drawImage("bgImage" + imageNo, 400, 500, null);
}The API suggests using getGraphics() to get the graphics context of a component. This allows you to invoke operations on the returned graphics object to draw on the component. When I try to call drawImage() i get the following error message:
Graphics/ThreadChangeBackground.java [57:1] cannot resolve symbol
symbol  : method drawImage (java.lang.String,int,int,<nulltype>)
location: class java.awt.Graphics
        changeable.getGraphics().drawImage("bgImage"+ imageNo, 400, 500, null);
                              ^
1 error
Errors compiling ThreadChangeBackground.If I change the code and try to do this:         g.drawImage("bgImage" + imageNo, 400, 500, null); everything complies but the background of my gui does not change. Adding changeable.repaint() to the loadImage() method does not change the gui background.
I've got this far by reading the API (it's so big!), java textbooks and the java tutorial, but I really don't know what to do next.
Any help would really be appreciated!

Answer 1

These are all the drawImage methods in Graphics class:
abstract boolean drawImage(Image img, int x, int y, Color bgcolor, ImageObserver observer)
Draws as much of the specified image as is currently available.
abstract boolean drawImage(Image img, int x, int y, ImageObserver observer)
Draws as much of the specified image as is currently available.
abstract boolean drawImage(Image img, int x, int y, int width, int height, Color bgcolor, ImageObserver observer)
Draws as much of the specified image as has already been scaled to fit inside the specified rectangle.
abstract boolean drawImage(Image img, int x, int y, int width, int height, ImageObserver observer)
Draws as much of the specified image as has already been scaled to fit inside the specified rectangle.
abstract boolean drawImage(Image img, int dx1, int dy1, int dx2, int dy2, int sx1, int sy1, int sx2, int sy2, Color bgcolor, ImageObserver observer)
Draws as much of the specified area of the specified image as is currently available, scaling it on the fly to fit inside the specified area of the destination drawable surface.
abstract boolean drawImage(Image img, int dx1, int dy1, int dx2, int dy2, int sx1, int sy1, int sx2, int sy2, ImageObserver observer)
Draws as much of the specified area of the specified image as is currently available, scaling it on the fly to fit inside the specified area of the destination drawable surface.
Notice that NONE of them takes String as the first argument.
Your error:
Cannot resolve symbol method drawImage (java.lang.String,int,int,<nulltype>)
suggests that java is looking for drawImage method that takes String as its first argument - IT'S NOT IN THE GRAPHICS CLASS - that's the problem
M
suggests