NetLogoStandalone.java

import java.io.*;
import java.net.*;
import javax.swing.*;

import org.nlogo.lite.InterfaceComponent;

/**
 * This is an example which tries to load a model from a URL, using InterfaceComponent.openFromSource().
 * This model will fail to work correctly because it references an image that it cannot find.
 * 
 * The model in question 
 *   http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/Bug%20Hunt%20Camouflage.nlogo
 * contains a reference to an image, which is located at 
 *   http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/poppyfield.jpg
 * 
 * When the model tries to execute its setup() procedure, it fails to find the image and throws the error:
 *     error while observer running IMPORT-DRAWING in procedure CHANGE-ENVIRONMENT
 *       called by procedure SETUP
 *     import-drawing: poppyfield.jpg (No such file or directory)
 *     (halted running of setup)
 *     
 * If we try to set the context of the model by specifying 
 *   app.setPrefix(new URL("http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/"));
 * Then we get:
 *     error [etc]
 *     import-drawing: /Users/sfentress/eclipse/otrunk-nlogo41/http:/ccl.northwestern.edu/netlogo/models/models/Sample%20Models
 *          /Biology/Evolution/poppyfield.jpg (No such file or directory)
 *  i.e. it starts from within the context that we are running the application
 *  
 *  If, instead of specifying "poppyfield.jpg" as the background image of the model, we change the model so that
 *  we specify the entire url (http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/poppyfield.jpg)
 *  we get:
 *     error [etc]
 *     import-drawing: /netlogo/models/models/Sample%20Models/Biology/Evolution/poppyfield.jpg (No such file or directory)
 *     
 *     
 * @author sfentress
 *
 */
public class NetLogoStandalone {
    public static void main(String[] argv) {
        try
        {
            final javax.swing.JFrame frame = new javax.swing.JFrame();
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            final InterfaceComponent app = new InterfaceComponent(frame);
            
            java.awt.EventQueue.invokeAndWait
                ( new Runnable()
                    { public void run() {
                     frame.setSize(1000,800);
                     frame.add(app);
                        frame.setVisible(true);
                        try {
                        	String source = getStringFromUrl(new URL("http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/Bug%20Hunt%20Camouflage.nlogo"));

//        					app.setPrefix(new URL("http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Evolution/"));			// this does not seem to help
                        	
                        	app.openFromSource("Model", null, source);
                        }
                        catch(Exception ex) {
                          ex.printStackTrace();
                        }
                    } } ) ;
        }
        catch(Exception ex) {
            ex.printStackTrace();
        }
    }
    
    /**
     *  returns a string of the contents of the file at the url
     */
	private static String getStringFromUrl(URL url){
		try {
	        InputStream inputStream = url.openStream();
	        ByteArrayOutputStream bout = new ByteArrayOutputStream();
	        byte [] buffer = new byte[1024];
	        int len;
	        while((len = inputStream.read(buffer)) > 0) {
	        	bout.write(buffer, 0, len);
	        }
	        return bout.toString();
        } catch (IOException e) {
	        e.printStackTrace();
        }
        return null;
	}
}