Loading image in Java J2ME

Question

I have a problem with loading image with java 2ME. I have a image file "picture.png" in location drive "C:". After that I wrote my like this to show image from this location.

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class ImageMidlet extends MIDlet implements CommandListener{
    private Display display;
    private Command exitCommand;
    private Command backCommand;
    private Command okCommand;
    private Form form;

    private ImageItem imageItem;
    private Image image;

    public ImageMidlet(){
        display = Display.getDisplay(this);
        form=new Form("");
        exitCommand = new Command("Exit", Command.EXIT, 1);
        backCommand = new Command("Back", Command.BACK, 2);
        okCommand = new Command("OK", Command.OK, 3);

        try {
            image=Image.createImage("/picture.png");
            imageItem=new ImageItem(null,image,ImageItem.LAYOUT_NEWLINE_BEFORE,"");
        }
        catch(IOException ex){

        }
        form.append(imageItem);
        form.addCommand(okCommand);
        form.addCommand(exitCommand);
        form.addCommand(backCommand);
        form.setCommandListener(this);

        display.setCurrent(form);

    }

    public void commandAction(Command c,Displayable d){

    }

    public void startApp() {
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {
    }
}

It shows me this error:

Unable to create MIDlet Test.ImageMidlet
java.lang.NullPointerException
     at javax.microedition.lcdui.Form.append(Form.java:638)
     at Test.ImageMidlet.<init>(ImageMidlet.java:39)
     at java.lang.Class.runCustomCode(+0)
     at com.sun.midp.midlet.MIDletState.createMIDlet(+34)
     at com.sun.midp.midlet.Selector.run(Selector.java:151)

I am starting learn to develop, so please guide to do this.

Answer 1

Image.createImage(String name) loads the given image as a resource. Resources are loaded with Class.getResourceAsStream(name), which looks up the resources from classpath, not from your file system root.

You should put the image file in your classpath, which is usually the final application .jar file. Usually a folder called resources or res is created under the project, where the images are placed. The contents of this folder are then copied to the .jar file. In development phase you should be able to append your resource folder to the classpath with a command-line parameter (java -cp resources in Java SE) or with a similar IDE setting.

If you are really interested in loading the images from actual file system, you can use optional FileConnection API (http://developers.sun.com/mobility/apis/articles/fileconnection/). The handset support for this API is limited though. For static images the classpath is the way to go.