| Local Views | ||
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Local views provide an interactive means to concentrate on "parts of interest" in a diagram. The basic idea is to prepare only a small part of an entire diagram which is directly related to some node or edge of particular interest.
This feature is particularly useful when displaying large and complex graphs. It is possible to "focus" on a node or edge, e.g. by selection. The local view then displays the source and target node of an edge or the neighbors of a node, even if they are out of the display area of the entire graph.
Local views can be considered as multiple views of a common model graph with predefined filters for the most common usecases.
A local view can comprise the following filtered information, for example:
Class LocalViewCreator
is an abstract class whose implementations
create a local view (Graph2D) from a given model graph (Graph2D). Its central method is
updateViewGraph() which populates the local view graph,
applies an automatic layout and updates the
Graph2DView instances which display the local view.
The layouter which will be invoked upon updateViewGraph()
can be set using setLayouter().
By default an IncrementalHierarchicLayouter is used.
The yFiles API offers a number of predefined implementations for the most common use cases.
Node based view creator implementations:
LocalViewCreator.Neighborhood |
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| Description | Creates a local view including all nodes which can be reached within a given distance from the node in focus. Optionally, real end nodes of inter-edges can be shown. |
LocalViewCreator.CommonParentGroup |
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| Description | Creates a local view including all nodes within the same group. The container can be included in the view. |
LocalViewCreator.AncestorGroups |
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| Description | Shows the ancestors of the focused node in the hierarchy, i.e. its containing group node and the group node's ancestors. |
LocalViewCreator.FolderContents |
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| Description | Shows the contents of the focused folder node. |
Edge based view creator implementations:
LocalViewCreator.SourceAndTarget |
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| Description | Shows the source and target nodes of the focused edge. Optionally, real end nodes of an inter-edge can be shown. |
LocalViewCreator.EdgeGroup |
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| Description | Shows the source and target nodes of all edges of a given group. An edge group can be defined as all edges with a common source and/or target or by edge groups as defined in the section called “Edge/Port Grouping (Bus-Style Edge Routing)”. |
Abstract implementation:
LocalViewCreator.AbstractLocalViewCreator |
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| Description | Abstract view creator which offers convenience methods to create local views based on focused graph elements. All other predefined implementations inherit from this class. |
Class LocalViewCreator offers getters for the model graph as well as for the local view graph.
It is up to the implementation to set the graph instances. The above listed predefined implementations
set the model graph in the constructor and create the local view themselves. The local view graph
then has to be set to the Graph2DView instance which should
display the local view as shown in Example 6.48, “Setting up a local view”.
Example 6.48. Setting up a local view
// 'localView' is of type y.view.Graph2DView. // 'modelGraph' is of type y.view.Graph2D. AbstractLocalViewCreator creator = new LocalViewCreator.Neighborhood(modelGraph); localView.setGraph2D(creator.getViewGraph());
AbstractLocalViewCreator and the predefined implementations offer convenience methods to
create local views based on one or more graph elements which are focused. After setting the focused
element the new view is created by invocation of the method
updateViewGraph()
as shown in Example 6.49, “Creating a local view”.
void addFocusEdge(Edge edge) |
|
| Description | Handling focused edges. |
void addFocusNode(Node node ) |
|
| Description | Handling focused nodes. |
Example 6.49. Creating a local view
// 'creator' is of type y.view.LocalViewCreator.AbstractLocalViewCreator. // 'focusNode' is of type y.base.Node. creator.clearFocusNodes(); creator.addFocusNode(focusNode); creator.updateViewGraph();
In addition to creating a new local view programmatically, AbstractLocalViewCreator
offers the possibility to let the creation be triggered by hovering over a graph item or by selecting
a graph item. A selection trigger can be (de)activated automatically by using the add or remove methods.
A hover trigger has to be created by the method
createHoverTrigger()
and added as view mode to the Graph2DView instance which display the local view.
void addSelectionTrigger() |
|
| Description | Managing automatic triggers for hovering/selection. |
Technically, the local view graph is not a subset but a copy of the model graph. Thus, the node or edge
instance of the local view is different from the instance of the corresponding model.
LocalViewCreator therefore offers methods to get the model item for a given view item and
vice versa.
Node getModelNode(Node view) |
|
| Description | Mappings between model and view items. |
The tutorial demo application LocalViewDemo.java gives a detailed demonstration on how to use and set up the different predefined LocalViewCreator implementations. It also shows how to create a custom LocalViewCreator implementation based on the class AbstractLocalViewCreator.
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