Null Pointer in ISOMLayout

[Brian Michalk]

There is another unanswered thread here that appears to be about the same problem.

Exception in thread "main" java.lang.NullPointerException
    at edu.uci.ics.jung.algorithms.layout.ISOMLayout.adjustVertex(ISOMLayout.java:176)
    at edu.uci.ics.jung.algorithms.layout.ISOMLayout.adjust(ISOMLayout.java:139)
    at edu.uci.ics.jung.algorithms.layout.ISOMLayout.step(ISOMLayout.java:107)
    at edu.uci.ics.jung.algorithms.layout.LayoutDecorator.step(LayoutDecorator.java:58)
    at edu.uci.ics.jung.visualization.layout.ObservableCachingLayout.step(ObservableCachingLayout.java:59)
    at edu.uci.ics.jung.algorithms.layout.util.VisRunner.prerelax(VisRunner.java:62)
    at edu.uci.ics.jung.visualization.DefaultVisualizationModel.setGraphLayout(DefaultVisualizationModel.java:113)
    at edu.uci.ics.jung.visualization.DefaultVisualizationModel.<init>(DefaultVisualizationModel.java:74)
    at edu.uci.ics.jung.visualization.DefaultVisualizationModel.<init>(DefaultVisualizationModel.java:58)
    at edu.uci.ics.jung.visualization.BasicVisualizationServer.<init>(BasicVisualizationServer.java:139)
    at drawAlert(EricsAnalytics.java:244)

With the offending code:

    public static void drawAlert(DirectedSparseMultigraph<Node, String> g, String caption)
    {
        //The function transform describes how a vertex s should be colored when processed by the drawing algorithm
        Transformer<Node,Paint> vertexColor = new Transformer<Node,Paint>() {     
            public Paint transform(Node s)
            {
                return s.getColor();
            } 
        }; 
        Transformer<Node,String> stringLabeller = new Transformer<Node,String>() {
            public String transform(Node s)
            {
                return s.getName();
            }
        };
        Layout<Node, String> layout = new ISOMLayout<Node, String>(g);
        layout.setSize(new Dimension(500,500)); // sets the initial size of the space
        BasicVisualizationServer<Node, String> bvs = new BasicVisualizationServer<Node, String>(layout);
        bvs.setPreferredSize(new Dimension(500,500));
        bvs.getRenderContext().setVertexLabelTransformer(stringLabeller);
        bvs.getRenderContext().setVertexFillPaintTransformer(vertexColor);
        JFrame frame = new JFrame("Simple Graph View");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(bvs);
        frame.pack();
        frame.setVisible(true);
    }

It appears that at this point:

BasicVisualizationServer<Node, String> bvs = new BasicVisualizationServer<Node, String>(layout);

The error is thrown, and it appears to be a threading problem.  If I change the layout to circle layout, and step through, it will mostly complete.  But ISOMlayout always gives me problems.  I'm trying to draw about 500 nodes.  If I reduce my graph to a few nodes, it sometimes works correctly.

[Anonymous]

I am receiving the same Error. Did anyone come across any solution?

[Jens Einloft]

This error occurs in my project every time i try to create the layout with an empty graph (no nodes or edges).
Other layouts work without this error. I posted it a time ago, but no answer. If you need this layout, you have to fix the ISOMLayout or wait for an update. (Or add a pseudonode to the graph and after creating the BVS, remove him)