Concurrent modification exception with Swing; getNode() method not yet implemented

["Steven E. Noel" <snoel AT gmu.edu>]

I have a question that involves GraphStream within a Swing GUI.  I know that is slightly out of scope of GraphStream per se, but my investigations led to a final question that I think is relevant.

 

I followed the tutorial in integrating a GraphStream viewer in a Swing GUI (http://graphstream-project.org/doc/Tutorials/Graph-Visualisation_1.1/#integrating-the-viewer-in-your-gui) and everything was ok.  My problem was later getting a ConcurrentModificationException while trying to modify a graph in response to a Swing event.

 

My goal is to be able to handle Swing events (buttons, etc.) to dynamically update a GraphStream graph (modify styles, etc.).  I wrote a small test of that.  Here is an excerpt:

 

/* =============================== */

import java.util.Collection;

import org.graphstream.graph.Node;
import org.graphstream.ui.graphicGraph.GraphicGraph;
import org.graphstream.ui.swingViewer.Viewer;

public class ToggleGreen {
    javax.swing.JToggleButton button;
    public javax.swing.JToggleButton getButton() {return button;}
    public void setButton(javax.swing.JToggleButton button) {this.button = button;}

 

    private static GraphicGraph graph = null;
    public GraphicGraph getGraph() {return graph;}
    public void setGraph(GraphicGraph _graph) {graph = _graph;}

    ToggleGreen(Viewer networkViewer) {
        setGraph(networkViewer.getGraphicGraph());  

        button = new javax.swing.JToggleButton("Green",  false);
        button.addItemListener (new java.awt.event.ItemListener() {

            public void itemStateChanged(java.awt.event.ItemEvent event) {
                if (button.isSelected()) {
                    System.out.println("Green ON");
                    /* This throws 
                     *  Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationException
                     *   at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
                     *   at java.util.HashMap$KeyIterator.next(Unknown Source)
                     *  at org.graphstream.ui.graphicGraph.StyleGroupSet$ElementIterator.next(StyleGroupSet.java:1419)
                     *  at org.graphstream.ui.graphicGraph.StyleGroupSet$ElementIterator.next(StyleGroupSet.java:1403)
                     *  at ToggleGreen$1.itemStateChanged(ToggleGreen.java:33) */
                    for (Node node: getGraph().getEachNode()) {
                        node.addAttribute("ui.style", "fill-color:green;");
                    }

 

                    /* This throws
                     *  Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: not implemented !
                     *  at org.graphstream.ui.graphicGraph.GraphicGraph.getNode(GraphicGraph.java:1223)
                     *  at ToggleGreen$1.itemStateChanged(ToggleGreen.java:42) */
                    //Collection<Node> nodeSet = getGraph().getNodeSet();
                    //for (int i = 0; i < nodeSet.size(); i++) {
                    //    Node node = getGraph().getNode(i);
                    //    node.addAttribute("ui.style", "fill-color:green;");
                    //}
                }
            }
        });
    }
}
/* =============================== */

 

This class creates a JToggleButton, which I added to my GUI, along with a GraphStream viewer.  The instatiated viewer is passed into this class, giving a handle to the graph in the viewer.  The button event then attempts to add a green color to each graph node.

 

With the code above, this throws the concurrent modification exception (after painting a single node green).  I am somewhat new to Swing, but I see that this is a well-known problem with iterating over Java Collections within threads.  I tried various suggestions such as synchronized(), but was never successful in eliminating the concurrent modification exception.  As a sanity check, I tested that

 

    for (Node node: getGraph().getEachNode()) {

        node.addAttribute("ui.style", "fill-color:green;");

        }

 

works fine outside of the Swing thread.

 

Another suggestion I saw was to reference the list/array using its index rather than an iterator, which is commented out in the code example.  That is this:

 

    for (int i = 0; i < nodeSet.size(); i++) {

        Node node = getGraph().getNode(i);

        node.addAttribute("ui.style", "fill-color:green;");

    }

 

For this, I get "java.lang.RuntimeException: not implemented !"  Presumably this is coming from a GraphStream try/catch, indicating that the getNode() method is not yet implemented?

 

Thanks in advance for any suggestions.

 

Regards,

Steve