The version of JGraph that you downloaded uses a newer version of Java (11) than the one that Matlab supports (8). You need to either (1) find an earlier version of JGraph that uses Java 8 (or earlier), or alternatively (2) make Matlab use Java 11 (or later) run-time engine (JRE) . Among these two alternatives, #1 is safer and easier.

Warning: A Java exception occurred trying to load the com/mxgraph/view/mxGraph class:
Java exception occurred:
java.lang.UnsupportedClassVersionError: com/mxgraph/view/mxGraph has been compiled by a more recent version of
the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions
up to 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.mathworks.jmi.OpaqueJavaInterface.findClass(OpaqueJavaInterface.java:137)
Error using javaObjectEDT
No class com.mxgraph.view.mxGraph can be located on the Java class path

Perhaps you tried to access the class before you used javaaddpath to add the JAR file to the classpath. If Matlab fails to find a class, then it will not be able to access it even after adding to the classpath – the only solution is to restart Matlab and to remember to add the JAR file to the classpath before trying to access the class.

graph = com.mxgraph.view.mxGraph
Undefined variable "com" or class "com.mxgraph.view.mxGraph".

if i use

graph = javaObjectEDT('com.mxgraph.view.mxGraph');
Error using javaObjectEDT
No class com.mxgraph.view.mxGraph can be located on the Java class path

i checked the dynamic javapath and it has the mentioned jar file listed

codec = com.mxgraph.io.mxCodec;
mxUtils = com.mxgraph.util.mxUtils;

graph_xml = mxUtils.getXml(codec.encode(graph.getModel()))
mxUtils.writeFile(graph_xml,'test.xml' );

 

@Sam – thanks for the detailed feedback 🙂

PS – I don’t know if you’ve downloaded it yet, but the prerelease of R2015b does actually contain a new suite of functionality for graphs. There’s a new graph object, and it has lots of great functionality for graph-theoretic work, such as shortest paths and minimum spanning trees. It also contains graph layout and plotting functions – unfortunately, at the moment these are not even 1% as nice looking as JGraph. But I’m sure they’ll be improving that in future releases.

I’ve used JGraphX quite a bit within MATLAB UIs, and have a couple of suggestions based on my experience.

i) When you create the mxGraphComponent, I’d make sure to explicitly put it on the EDT, as you’ve done in your post for the mxGraph. In other words, rather than

graphComponent = com.mxgraph.swing.mxGraphComponent(graph);

I’d write

graphComponent = javaObjectEDT('com.mxgraph.swing.mxGraphComponent', graph);

That should make sure there are no threading issues.

ii) Rather than making a JPanel, adding the graphcomponent to the JPanel, and then using javacomponent to insert the JPanel into a figure as you do above, I would just make a regular MATLAB uipanel in the figure, and then use javacomponent to place the graphcomponent into the uipanel. A uipanel is basically a JPanel anyway, but again it has wrappers that will manage any threading issues that might arise.

iii) I’ve found that, by default, the graphcomponent contains several mouse listeners that interfere with callbacks that I’m trying to create. So I’ve found it useful to remove them all before creating my own. You can do this using something like the following code:

graphControl = graphComponent.getGraphControl;
mls  = graphControl.getMouseListeners;
mmls = graphControl.getMouseMotionListeners;
for i = 1:numel(mls)
    graphControl.removeMouseListener(mls(i))
end
for i = 1:numel(mmls)
    graphControl.removeMouseMotionListener(mmls(i))
end

iv) Instead of javax.swing.SwingUtilities.isRightMouseButton(eventData), you can just use eventData.getButton, which equals 1 for the left button or 3 for the right button. You can also use eventData.isShiftDown or eventData.isControlDown to detect key modifiers on the mouse click.

Hope that’s useful for people!

Sam