The classes IlvLinkImage and
IlvHyperEdge
differ in the following areas:
Orientation
Normal links (
IlvLinkImage
) have a flag that indicates whether they are oriented. If the
links are oriented, an arrowhead will be drawn. The orientation
flag is necessary because, if an arrowhead were always drawn,
then there would be no way of drawing a link between two nodes
that did not represent a flow direction.
Hyperedges are always oriented. Therefore,
an arrowhead is drawn at the target nodes and this arrowhead
cannot be switched off.
This feature is not a restriction. If you
want to draw a hyperedge between several nodes without an
arrowhead, create a hyperedge that has all these nodes as
sources, but has no target node.
You can also create a hyperedge that has
only target nodes, but no source node. In this case, an arrowhead
is drawn at all end nodes of the hyperedge.
You can see that hyperedges are much more
flexible than normal links.
If a hyperedge has exactly one source node
and one target node, then it will look like, and behave
approximately as, a normal oriented link.
If a hyperedge has exactly two source
nodes and zero target nodes, then it will look like a normal
unoriented link.
Changing end nodes of a link
To change the end nodes of an
IlvLinkImage
object, you must remove the
IlvLinkImage
from the graph. Then you must change the end nodes and reinsert
the link into the graph.
Changing the end nodes of an IlvHyperEdge object is more convenient. The
end nodes can be changed while the hyperedge remains in the
hypergraph. For example, you can add an empty hyperedge with zero
end nodes to the hypergraph. Then you can add source and target
nodes later. You must encapsulate all operations that change the
end nodes of a hyperedge into applyToObject sessions. See Modifying geometric properties of objects
in The Essential Features of
JViews Framework user documentation for more details.
The operations that can be carried out on
IlvHyperEdge
are shown in the following table.
Operations on IlvHyperEdge
Operation
|
Description
|
|---|---|
setFrom(nodeVector)
|
Removes
all old source nodes from the hyperedge and adds all nodes
contained in the input vector as new source nodes of the
hyperedge. |
setTo(nodeVector)
|
Removes
all old target nodes from the hyperedge and adds all nodes
contained in the input vector as new targets of the
hyperedge. |
addFrom(node)
|
Adds
the input node to the list of source nodes of the hyperedge.
|
addTo(node)
|
Adds
the input node to the list of target nodes of the hyperedge.
|
removeFrom(node)
|
Removes
the input node from the list of source nodes of the
hyperedge. |
removeTo(node)
|
Removes
the input node from the list of target nodes of the
hyperedge. |
The following code example shows how to
create an empty hyperedge, add it to the hypergraph, and then add
some source nodes.
Creating an empty hyperedge and adding
source nodes
IlvHyperGrapher grapher = new IlvHyperGrapher();
grapher.setMinHyperEdgeEndCount(0);
...
IlvHyperEdge edge = new IlvHyperEdge();
grapher.addHyperEdge(edge, false);
...
grapher.applyToObject(edge,
new IlvApplyObject() {
public void apply(IlvGraphic obj, Object arg) {
((IlvHyperEdge)obj).addFrom(node1);
((IlvHyperEdge)obj).addFrom(node2);
((IlvHyperEdge)obj).addFrom(node3);
}
}, arg, redraw);