✔ Nullpointerexception

[Carina]

Hallo ich bin Anfängerin in Java, habe große Probleme und versuche seit 2 Tagen eins zu lösen, komme aber leider nicht zur Lösung ich hoffe ihr könnt mir dabei helfen. Wenn ich das Programm ausführe spuckt mir Eclipse folgende Fehlermeldung:

Exception in thread "main" java.lang.NullPointerException
at de.hohenheim.controller.Fahrplan.getNodeNames(Fahrplan.java:39)
at de.hohenheim.controller.Fahrplan.open(Fahrplan.java:58)
at de.hohenheim.controller.Fahrplan.run(Fahrplan.java:26)
at de.hohenheim.controller.ControllerCanvas$4.handleEvent(ControllerCanvas.java:176)

ich füge mal die jeweiligen Stellen ein:

ControllerCanvas

public void handleEvent(Event arg0) {
				Fahrplan dialog = new Fahrplan();
				dialog.run();
			}
		});

Fahrplan

private String[] getNodeNames() {
		Object[] names = map.getNodes().keySet().toArray();
		String[] n = new String[names.length];
		for (int i = 0; i < names.length; i++) {
			n[i] = names[i].toString();
		}
		Arrays.sort(n);
		return n;


System.out.println("Button pressed, about to open modal dialog");
		        final Shell dialogShell = new Shell();
		        dialogShell.setLayout(new FormLayout());
		        {
		        	final Combo node_combo = new Combo(dialogShell, SWT.READ_ONLY);
		    		node_combo.setBounds(5, 45, 150, 25);
		    		String[] items = getNodeNames();
		    		node_combo.setItems(items);
		        }
	}

Ich würde mich riesig auf eine Antwort freuen

LG Carina

 

[sheel]

Hi

Java ist nicht Javascript. Thread verschoben.

Welche der gezeigten Zeilen ist Zeile 39?

 

[Carina]

private String[] getNodeNames() {
		Object[] names = map.getNodes().keySet().toArray();
		String[] n = new String[names.length];
		for (int i = 1; i < names.length; i++) {
			n[i] = names[i].toString();
		}
		Arrays.sort(n);
		return n;
	}

Hier die 2. zeile

 

[sheel]

Dann gibt es map, map.getNodes(), oder map.getNodes().keySet() nicht.
Ohne mehr Code kann man da schwer etwas sagen.
Was ist map? Sicher, dass es vorher erzeugt wird?

 

[Carina]

Ja das wird in einer anderen Klasse erzeugt, es stellt einen gleisbahn dar auf dem ich später einen Fahrplan simulieren soll. Der Inhalt der Nodemap Klasse sieht wie folgt aus :

import java.util.ArrayList;
import java.util.HashMap;
import org.eclipse.draw2d.Figure;
import org.eclipse.draw2d.LightweightSystem;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;


import de.hohenheim.view.mobile.AnimationFigure;
import de.hohenheim.view.path.PathFigure;
import de.hohenheim.view.node.NodeFigure;

public class NodeMap {
	
	/**
	 * This HashMap Contains all mobile objects, such as trains, ....
	 */
	HashMap<String, AnimationFigure> mobile_objects = new HashMap<String, AnimationFigure>();
	
	/**
	 * This HashMap Contains all paths of all rooms in the NodeMap. The paths are added automatically, when the methods of FigureFactory
	 * are used to create the Figures in the Map.
	 */
	HashMap<NodeFigure, ArrayList<PathFigure>> paths = new HashMap<NodeFigure, ArrayList<PathFigure>>();
	/**
	 * This HashMap Contains all rooms in the NodeMap. The paths are added automatically, when the methods of FigureFactory
	 * are used to create the Figures in the Map.
	 */
	HashMap<String, NodeFigure>  nodes = new HashMap<String, NodeFigure>();
	
	/**
	 * On this figure all rooms are drawn.
	 */
	NodeLayerFigure nodeLayer;
	/**
	 * On this figure all figures which can be animated must be drawn.
	 * It is a transparent layer for the animations.
	 */
	AnimationLayerFigure animationLayer;
		
	/**
	 * 
	 * @return Figure - The Layer where the rooms are drawn onto. 
	 */
	public Figure getNodeLayer() {
		return this.nodeLayer;
	}
	
	/**
	 * 
	 * @return Figure - The Figure where the animations are drawn (AnimationLayerFigure).
	 */
	public Figure getAnimationLayer() {
		return this.animationLayer;
	}
	
	/**
	 * Returns a HasMap with all movable objects inside this RoomMap. 
	 * @return HashMap
	 */
	public HashMap<String, AnimationFigure> getMobileObjects() {
		return this.mobile_objects;
	}
	
	/**
	 * Returns the HashMap which contains all paths of all rooms in this RoomMap.
	 * Key of the {@link HashMap} is the room (RoomFigure). Value is an {@link ArrayList} with all paths (PathFigure)
	 * which are connected to this room.
	 * @return {@link HashMap}
	 */
	public HashMap<NodeFigure, ArrayList<PathFigure>> getPaths() {
		return this.paths;
	}
	/**
	 * Returns the HashMap which contains all rooms in this RoomMap.
	 * Key of the {@link HashMap} is the name of the room as {@link String}. Value is an {@link ArrayList} with all paths ({@link PathFigure})
	 * which are connected to this room.
	 * @return {@link HashMap}
	 */
	public HashMap<String, NodeFigure> getNodes() {
		return this.nodes;
	}
	/**
	 * Constructor to create a new RoomMap	
	 * @param {@link String} roomName - the name of the RoomMap. The name is displayed in the titlebar. 
	 */
	public NodeMap(Canvas c) {
		nodeLayer = new NodeLayerFigure();
	    animationLayer = new AnimationLayerFigure();
	    createNodeContents(c);
	}
	
	/**
	 * Returns the default display. Perhaps we must use another later, 
	 * that is why we let it stay here...
	 * @return {@link Display}
	 */
	public Display getDisplay() {
		return Display.getDefault();
	}
	
	/**O
	 * Initializes the lightweightsystem and the layers for drawing.
	 * @param {@link Canvas} c - the canvas where the lightweight system runs on.  
	 */
	private void createNodeContents(Canvas c) {		
		LightweightSystem lws = new LightweightSystem(c);
		BackgroundLayerdPane layers = new BackgroundLayerdPane();
	    lws.setContents(layers);
	    layers.add(nodeLayer);
	    layers.add(animationLayer);
	}
}