It’s a MathWorks-authored component, although it may (I’m not sure) be a wrapper around a third-party component. I’m not sure why it’s included as part of MATLAB rather than just SimBiology – perhaps there’s an idea that it might get reused across other products as well.

If anyone is thinking of using it, I would not rely on it to have a stable interface or behaviour across versions: MathWorks may well modify it based on requirements for SimBiology – which, as a leaf product, has much more scope to change rapidly than core MATLAB.

Overload the mxGraph class. Create a file, mymxGraph.java with the following code:

import java.awt.datatransfer.DataFlavor;
import com.mxgraph.view.mxGraph;
import com.mxgraph.swing.util.mxGraphTransferable;
 
// Modified mxGraph to fix dragging
public class mymxGraph extends mxGraph {
  static {
    try {
      //Set enableImageSupport to false if using Mac otherwise data translation error happens.
      com.mxgraph.swing.util.mxGraphTransferable.enableImageSupport = false;
      //Following code is suggested in:
      //https://github.com/jgraph/jgraphx/blob/master/src/com/mxgraph/swing/util/mxGraphTransferable.java
      mxGraphTransferable.dataFlavor = new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType + 
      "; class=com.mxgraph.swing.util.mxGraphTransferable", null, 
      new com.mxgraph.swing.util.mxGraphTransferable(null, null).getClass().getClassLoader()); 
    } catch (ClassNotFoundException e) {
      System.err.println("Caught Class Not Found Exception: " + e.getMessage());;
    }
  }
}

Next, compile the class (at Matlab command line). Note that I have the jgraphx.jar in the same folder as mymxGraph.java created above which is also my Current Folder in Matlab:

% Compile the java file being sure to include jgraphx.jar
system('javac mymxGraph.java -classpath jgraphx.jar')
% Create a jar
system('jar cf mymxGraph.jar mymxGraph.class')
% Add both mymxGraph and jgraphx to java path
javaaddpath('mymxGraph.jar');
javaaddpath('jgraphx.jar')
 
% Replace com.mxgraph.view.mxGraph with the new mymxGraph
graph = mymxGraph;
 
%Run the rest of the code above and cells should now be draggable.

I’m a java amateur so if anyone has improvements to suggest please post them.

Thanks

You don’t need to patch jgraphx’ sources.
From your code I see that you use jgraphx directly on Matlab’s command line (or in a .m file).
I wrote a Java program (where I put my code snippet in right at the beginning), compiled and packed it into a jar. From Matlab’s command line, I use that jar as a kind of library.

I’ve been trying to get this working.

Do i need to put this code in my own program or in the jgraphx sources and rebuild it?

I’ve tried running it from my program with no success. I use jgraphx directly from matlab so i rewrote the code snippet for matlab:

%Fix for movable vertices
tempobj = javaObject('com.mxgraph.swing.util.mxGraphTransferable',[], []);
mxGraphTransferable.dataFlavor = javaObject('java.awt.datatransfer.DataFlavor', ...
   [char(java.awt.datatransfer.DataFlavor.javaJVMLocalObjectMimeType)'; class = com.mxgraph.swing.util.mxGraphTransferable'], ...
   [], tempobj.getClass().getClassLoader())

What am I doing wrong?

Regards

People complained about not being able to move vertices if they start a java application built with mxGraph/JGraph. I experienced the same problem and investigated it. Here’s my solution how to get it working.
This article refers to Matlab R2013a and mxGraph 2.1.0.0 but it should also work with older versions of both.

Both Drag & Drop (which is needed for moving vertices around) and Cut & Paste rely on the mxGraphTransferHandler working correctly. The mxGraphTransferHandler in fact uses its own implementation of Transferable (java.awt.datatransfer.Transferable) called mxGraphTransferable. Have a look at the source code in jgraphx/src/com/mxgraph/swing/util/mxGraphTransferable.java. At the very end you’ll see a static initializer whose job is to construct a suitable DataFlavor (java.awt.datatransfer.DataFlavor). And here is the problem! If you start your mxGraph application from Java’s VM everything works fine. But if you start it from within Matlab’s JVM it cannot find the class com.mxgraph.swing.util.mxGraphTransferable and you’ll get a ClassNotFoundException. As you can see in the code this one is caught but nothing happens (// do nothing). So you do not notice that the Class Loader has a problem and keep wondering why moving vertices does not work (as me).

Now here comes the solution. By the way, I found it in the source code jgraphx/src/com/mxgraph/swing/util/mxGraphTransferable.java at the very top. There it says “Serialized Data Flavor. Use the following code to switch to local reference flavor: …”. In fact this did not work for me. “If you get a class not found exception, try the following instead: …” Et voila! Just insert their code

mxGraphTransferable.dataFlavor = new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType
+ "; class=com.mxgraph.swing.util.mxGraphTransferable", null,
new com.mxgraph.swing.util.mxGraphTransferable(null, null).getClass().getClassLoader());

at the beginning of your java code and moving vertices, Drag & Drop and Cut & Paste works!

Does anyone know what can be the problem?

Cheers

(Version R2008a, Windows Vista)