SWT XML Sprite Sheet Utility

[Lance Colton]

I'm trying to create a class, which will take a path to an Image, and an XML file which defines sub-images within the image, and return each sub image as SWT Image objects.

It basically should work like this

String xml = "data/menu.png.xml";
String image = "data/menu.png";
final XMLSpriteSheet testSheet = new XMLSpriteSheet(display, image, xml);
GC.drawImage(testSheet.getSprite("play.png"), 0, 0);

with the XML Sprite sheet looking like this

public class XMLSpriteSheet {	
	/** The sprite sheet. */
	private Image sheet;
	
	/** The xml file. */
	private File xml;
	
	/** stores sprite data */
	private LinkedList<HashMap<String, String>> spriteSheet;
	
	/** stores sub-images */
	private HashMap<String, Image> sprites;
	
	/**
	 * Instantiates a new xML sprite sheet.
	 *
	 * @param sheet the sprite sheet
	 * @param xml the xml file
	 */
	public XMLSpriteSheet(Display display, String sheet, String xml) {
		this.sheet   = new Image(display, sheet);
		this.xml     = new File(xml);
		
		spriteSheet = new LinkedList<HashMap<String, String>>();
		sprites     = new HashMap<String, Image>();
		
		processXML();
		populateSpriteList(display);
	}

	private void processXML() {
            //processes the XML
	}
	
	private void populateSpriteList(Display display) {
		for( HashMap<String, String> map : spriteSheet ) {
			int width  = Integer.parseInt(map.get("width"));
			int height = Integer.parseInt(map.get("height"));
			int x = Integer.parseInt(map.get("x"));
			int y = Integer.parseInt(map.get("y"));
			String name = map.get("name");
			
			/** create our image */
			Image image = new Image(display, width, height);
			GC gc = new GC(image);
			gc.drawImage(sheet, x, y, width, height, 0, 0, width, height);
			gc.dispose();
			
			sprites.put(name, image);
		}
	}
	
	public Image getSprite(String name) {
		return( sprites.get("name") );
	}
}

I think the problem is SWT doesn't like for the display object to be passed to an outside class, is there any way to resolve this?

The stack trace:

Exception in thread "main" java.lang.IllegalArgumentException: Argument cannot be null
	at org.eclipse.swt.SWT.error(SWT.java:4064)
	at org.eclipse.swt.SWT.error(SWT.java:3998)
	at org.eclipse.swt.SWT.error(SWT.java:3969)
	at org.eclipse.swt.graphics.GC.drawImage(GC.java:724)
	at org.derpdrive.game.XMLTest$1.paintControl(XMLTest.java:25)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:223)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1282)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1267)
	at org.eclipse.swt.widgets.Control.gtk_expose_event(Control.java:2783)
	at org.eclipse.swt.widgets.Composite.gtk_expose_event(Composite.java:701)
	at org.eclipse.swt.widgets.Canvas.gtk_expose_event(Canvas.java:167)
	at org.eclipse.swt.widgets.Shell.gtk_expose_event(Shell.java:1204)
	at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:1739)
	at org.eclipse.swt.widgets.Control.windowProc(Control.java:4796)
	at org.eclipse.swt.widgets.Display.windowProc(Display.java:4360)
	at org.eclipse.swt.internal.gtk.OS._gtk_main_do_event(Native Method)
	at org.eclipse.swt.internal.gtk.OS.gtk_main_do_event(OS.java:8168)
	at org.eclipse.swt.widgets.Display.eventProc(Display.java:1238)
	at org.eclipse.swt.internal.gtk.OS._g_main_context_iteration(Native Method)
	at org.eclipse.swt.internal.gtk.OS.g_main_context_iteration(OS.java:2229)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3159)
	at org.derpdrive.game.XMLTest.main(XMLTest.java:30)

The is the result of me trying to draw a returned image to a Canvas in a Shell with the same Display.

[Rob Spoor]

Are you sure that sprites.containsKey("play.png") returns true? In other words, that sprites.get("play.png") does not return null?
You are calling sprites.get("name") - using the String literal "name" instead of the parameter name. As a results, the returned Image probably is null.

[Lance Colton]

Rob Spoor wrote:Are you sure that sprites.containsKey("play.png") returns true? In other words, that sprites.get("play.png") does not return null?
You are calling sprites.get("name") - using the String literal "name" instead of the parameter name. As a results, the returned Image probably is null.

Yes, each name in the <String, Image> HashMap is there, however the Image objects are all null. something is wrong with the image construction through GC, and I think it might have something to do with the Display object that had to be passed.

let me post the entire source code,

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.LinkedList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Display;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class XMLSpriteSheet {	
	/** The sprite sheet. */
	private Image sheet;
	
	/** The xml file. */
	private File xml;
	
	/** stores sprite data */
	private LinkedList<HashMap<String, String>> spriteSheet;
	
	/** stores sub-images */
	private HashMap<String, Image> sprites;
	
	/**
	 * Instantiates a new xML sprite sheet.
	 *
	 * @param sheet the sprite sheet
	 * @param xml the xml file
	 */
	public XMLSpriteSheet(Display display, String sheet, String xml) {
		this.sheet   = new Image(display, sheet);
		this.xml     = new File(xml);
		
		spriteSheet = new LinkedList<HashMap<String, String>>();
		sprites     = new HashMap<String, Image>();
		
		processXML();
		populateSpriteList(display);
	}

	/**
	 * Process the xml file.
	 */
	private void processXML() {
		try {
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document doc = db.parse(xml);
			doc.getDocumentElement().normalize();
			NodeList nodeList = doc.getElementsByTagName("sprite");
			
			for( int i = 0; i < nodeList.getLength(); i++ ) {
				Node node = nodeList.item(i);
				Element element = (Element)node;
				
				HashMap<String, String> data = new HashMap<String, String>();
				data.put("name", element.getAttribute("name"));
				data.put("x", element.getAttribute("x"));
				data.put("y", element.getAttribute("y"));
				data.put("width", element.getAttribute("width"));
				data.put("height", element.getAttribute("height"));
				
				spriteSheet.add(data);
			}
			
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	private void populateSpriteList(Display display) {
		for( HashMap<String, String> map : spriteSheet ) {
			int width  = Integer.parseInt(map.get("width"));
			int height = Integer.parseInt(map.get("height"));
			int x = Integer.parseInt(map.get("x"));
			int y = Integer.parseInt(map.get("y"));
			String name = map.get("name");
			
//			int srcWidth  = sheet.getBounds().width;
//			int srcHeight = sheet.getBounds().height;
			
			/** The problem is somewhere below this. */
			Image image = new Image(display, width, height);
			GC gc = new GC(image);
			gc.drawImage(sheet, x, y, width, height, 0, 0, width, height);
			gc.dispose();

			sprites.put(name, image);
		}
	}
	
	public Image getSprite(String name) {
		return( sprites.get("name") );
	}
}

Here is the XML:
<?xml version="1.0"?> <sheet> <sprite name="play.png" x="0" y="0" width="241" height="92" /> <sprite name="quit.png" x="0" y="92" width="241" height="92" /> <sprite name="pointer_cat.png" x="0" y="225" width="79" height="82" /> </sheet>

[Rob Spoor]

But you're not calling sprites.get("play.png"), you're calling sprites.get("name").

[Lance Colton]

Rob Spoor wrote:But you're not calling sprites.get("play.png"), you're calling sprites.get("name").

There are no words, to express, how retarded I feel for that XD

Thank you so much, it works perfectly now.

[Rob Spoor]

It's the kind of mistake everybody makes at least once. But you're welcome