how to use drawImage in an object

[Jeff Borland]

help!
im a teacher with a java class (1st time) and kids love using drawImage. now i want them to put it in individual classes. but now the drawImage doesnt work. any ideas? thanks, jeff
in an object
public void draw(Graphics g)
{
Image smallSub=getImage(getCodeBase(),"LittleHopper.jpg");
g.drawImage(smallSub,230+subX, 240+subY, this);
}
which is initialized, then called in main interface:
public void paint(Graphics g)
{

player.draw(g);
}

[Craig Wood]

    public void draw(Graphics g)
    {
        Image smallSub=getImage(getCodeBase(),"LittleHopper.jpg");
        g.drawImage(smallSub,230+subX, 240+subY, this);
    }

It is not efficient to load a new image with each call to draw.
Also, the getImage method returns immediately, not waiting for the image to finish loading. So if LittleHopper has any size to it you won't get anything to show up from the call to draw. Not right away anyway.

A more efficient way is to load the image only once, in or via a method call from either init (Applet) or a constructor (class, such as Player). Looks like you are working with an older sdk so I used MediaTracker in the example. Although you might get by fine without a MediaTracker it is an option and will ensure that the image is fully loaded before you attempt to render it.

/*  <applet code="DrawingImages" width="400" height="400"></applet>
 *  use: appletviewer DrawingImages.java
 */
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
 
public class DrawingImages extends Applet
{
    public void init()
    {
        setLayout(new BorderLayout());
        add(new ImageDrawingPanel());
    }
 
    public static void main(String[] qrgs)
    {
        Applet applet = new DrawingImages();
        Frame f = new Frame();
        f.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
        f.add(applet);
        f.setSize(400,400);
        f.setLocation(200,200);
        applet.init();
        applet.start();
        f.setVisible(true);
    }
}
 
class ImageDrawingPanel extends Panel
{
    Image image;
 
    public ImageDrawingPanel()
    {
        loadImage();
    }
 
    public void paint(Graphics g)
    {
        super.paint(g);
        int w = getWidth();
        int h = getHeight();
        draw1(g, w, h);
        draw2(g, w, h);
        draw3(g, w, h);
    }
 
    private void draw1(Graphics g, int w, int h)
    {
        g.drawImage(image, w/4, h/4, this);
    }
 
    private void draw2(Graphics g, int w, int h)
    {
        g.drawImage(image, w*3/4, h/2, this);
    }
 
    private void draw3(Graphics g, int w, int h)
    {
        g.drawImage(image, w*3/4, h*3/4, this);
    }
 
    private void loadImage()
    {
        String fileName = "images/dukeWaveRed.gif";
        MediaTracker tracker = new MediaTracker(this);
        image = Toolkit.getDefaultToolkit().getImage(fileName);
        tracker.addImage(image, 0);
        try
        {
            tracker.waitForID(0);
        }
        catch(InterruptedException ie)
        {
            System.out.println(ie.getMessage());
        }
    }
}

[Dirk Schreckmann]

Moving this to the Swing / JFC / AWT forum...

[Jeff Borland]

Craig Wood,
thanks so much for your reply. my problem is not w/ the image loading in a class (yes, normally i load my image in the init, i was just shrotening the code for demo purposes).
my problem is i have two classes and having the second one drawImages. for example
MAIN GAME - calls SUBMARINE
when another iteration of the game happens, i want the drawing done in a method of submarine like draw. It works fine for all none images (jpg,gif). is there a way to do this you know?
thanks so much for any help.
also thanks for your last reply, it was incredibly extensive.

[Craig Wood]

In the applet code below we could just as well load the single image in the ImageDrawingPanel class and send a reference along in each Duke constructor:

    private void loadDukes()
    {
        dukeList.add(new Duke(image, 10, 10));
    . . .
class Duke extends Panel
{
    Image image;
    int x,y;
 
    public Duke(Image image, int x, int y)
    {
        this.image = image;
        . . .

Or we could leave it as is and send a (potentially different) fileName string into each new Duke constructor. In this case we would also have to change moveDuke to keep the dukes inside their boundries:

    private void moveDuke()
    {
        int w = getWidth();
        int h = getHeight();
 
        for(int j = 0; j < dukeList.size(); j++)
        {
            Duke duke = (Duke)dukeList.get(j);
            int imageWidth = ((Duke)dukeList.get(j)).image.getWidth(this);
            int imageHeight = ((Duke)dukeList.get(j)).image.getHeight(this);
            int x = seed.nextInt(w - imageWidth);
            int y = seed.nextInt(h - imageHeight);
            duke.move(x, y);
        }
        repaint();
    }

/*  <applet code="DrawingImages" width="400" height="400"></applet>
 *  use: appletviewer DrawingImages.java
 */
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;
import java.util.List;
import javax.imageio.ImageIO;
 
public class DrawingImages extends Applet
{
    public void init()
    {
        ImageDrawingPanel panel = new ImageDrawingPanel();
        setLayout(new BorderLayout());
        add(panel.getUIPanel(), "North");
        add(panel);
    }
 
    public static void main(String[] qrgs)
    {
        Applet applet = new DrawingImages();
        Frame f = new Frame();
        f.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
        f.add(applet);
        f.setSize(400,400);
        f.setLocation(200,200);
        applet.init();
        applet.start();
        f.setVisible(true);
    }
}
 
class ImageDrawingPanel extends Panel
{
    List dukeList;
    Random seed;
 
    public ImageDrawingPanel()
    {
        dukeList = new ArrayList();
        seed = new Random();
        loadDukes();
        setBackground(Color.white);
    }
 
    public void paint(Graphics g)
    {
        super.paint(g);
        for(int j = 0; j < dukeList.size(); j++)
        {
            Duke duke = (Duke)dukeList.get(j);
            duke.draw(g);
        }
    }
 
    private void loadDukes()
    {
        dukeList.add(new Duke(10, 10));
        dukeList.add(new Duke(75, 150));
        dukeList.add(new Duke(220, 195));
        dukeList.add(new Duke(60, 200));
    }
 
    private void moveDuke()
    {
        int w = getWidth();
        int h = getHeight();
        int imageWidth = ((Duke)dukeList.get(0)).image.getWidth(this);
        int imageHeight = ((Duke)dukeList.get(0)).image.getHeight(this);
 
        for(int j = 0; j < dukeList.size(); j++)
        {
            Duke duke = (Duke)dukeList.get(j);
            int x = seed.nextInt(w - imageWidth);
            int y = seed.nextInt(h - imageHeight);
            duke.move(x, y);
        }
        repaint();
    }
 
    public Panel getUIPanel()
    {
        Button move = new Button("move duke");
        move.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                moveDuke();
            }
        });
        Panel panel = new Panel();
        panel.add(move);
        return panel;
    }
 }
 
class Duke extends Panel
{
    Image image;
    int x, y;
 
    public Duke(int x, int y)
    {
        this.x = x;
        this.y = y;
        loadImage();
    }
 
    public void move(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
 
    public void draw(Graphics g)
    {
        g.drawImage(image, x, y, this);
    }
 
    private void loadImage()
    {
        String fileName = "images/dukeWaveRed.gif";
        try
        {
            URL url = getClass().getResource(fileName);
            image = ImageIO.read(url);
        }
        catch(MalformedURLException mue)
        {
            System.out.println("URL help: " + mue.getMessage());
        }
        catch(IOException ioe)
        {
            System.out.println("io trouble: " +  ioe.getMessage());
        }
    }
}

[Jeff Borland]

ken,
thanks so much, thats works great...
im so psyched.
once again, forums have restored my faith in the goodness of man. sounds like an exaggeration, but it is full of truth.
thanks again,
my class will be very appreciative
below is the link of my class if you're curious:
http://www.drborland.com/deering/java/index.htm

[Jeff Borland]

Ken,
quick? i went to school today and found out imageio lib does not exist in sdk1.3 (the only thing that would load on all the comps).
can i just copy my folder from 1.4 onto those machines or is there a better way?
(so it gave an error importing the javax.imageio
thanks,
jeff