JUNG Graph: TreeLayout for SparseMultigraph

0
votes

I am new to Jung. I need to visualize a tree containing severel nodes. It all works fine using a graph of type DelegateForest and a TreeLayout. However, when adding edges, the code runs into an exception, if edges are being added to the graph that are already in the tree. Exception is: "Exception in thread "main" java.lang.IllegalArgumentException: Tree must not already contain child x". In other words, if an edge is added that contains vertices, which are already in the graph, the above exception is thrown. The following example code demonstrates this:

Forest<Integer, String> g2 = new DelegateForest<Integer, String>();
g2.addVertex((Integer) 1);
g2.addVertex((Integer) 2);
g2.addVertex((Integer) 3);
g2.addVertex((Integer) 4);
g2.addVertex((Integer) 5);
g2.addEdge("Edge-1-3", 1, 3);
g2.addEdge("Edge-2-3-P", 2, 3); 
g2.addEdge("Edge-4-3-P", 4, 3); 
g2.addEdge("Edge-4-5-P", 4, 5); 
g2.addEdge("Edge-3-5-P", 3, 5);

Layout<Integer, String> layout = new TreeLayout<Integer, String>(g2);

VisualizationViewer<Integer, String> vv = new VisualizationViewer<Integer, String>(layout);
vv.setPreferredSize(new Dimension(800, 600));
vv.getRenderContext().setVertexLabelTransformer(new ToStringLabeller());
vv.getRenderContext().setEdgeLabelTransformer(new ToStringLabeller());
vv.getRenderer().getVertexLabelRenderer().setPosition(Position.CNTR);

JFrame frame = new JFrame("Simple Graph View");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(vv);
frame.pack();
frame.setVisible(true);

The exception is thrown on the line "g2.addEdge("Edge-3-5-P", 3, 5);"

So I understand that I have to use the graph type SparseMultigraph. Unfortunately, there is no layout that looks like the TreeLayout that one can use with the SparseMultigraph. Can you give me a hint on how to solve my problem?

Many thanks in advance!

2
javagraphjung
You can't use a TreeLayout for a graph that is not a tree (and when you add the edge 3-5, the graph is no longer a tree). You may consider a different layout, like SpringLayout or FRLayout... - Marco13

2 Answers

0
votes

The above comment is correct. That said, you can extract a spanning tree from the graph, lay that out with TreeLayout, and then use those positions to last out the entire Graph. The minimumspanningtree layout demo demonstrates this.

0
votes

this exception occur when you add child to one parent and same child to another parent, as in your case

g2.addEdge("Edge-4-5-P", 4, 5); g2.addEdge("Edge-3-5-P", 3, 5);

try to add unique child. specifically in TreeLayout. try another Layout, but i have not tried another layout yet.