Using layout algorithms through the graph layout API

Programmer's documentation > Using graph layout algorithms > Getting started with graph layout > Using layout algorithms through the graph layout API

Explains how to use layout algorithms through the graph layout API.

Using layout algorithms on graphers

Explains how to use a layout algorithm on a grapher.

Running the sample application that uses the graph layout API

Illustrates an application that uses a graph layout on a grapher.

Using layout algorithms on graphers

Graphers (class IlvGrapher).store nodes and links and provide the minimal infrastructure that is necessary to perform a graph layout.

To use the layout algorithms provided by the graph layout package:

1. Create a grapher object ( IlvGrapher ) and fill it with nodes and links.

2. Create an instance of the layout algorithm (any subclass of IlvGraphLayout).

3. Declare a handle for the corresponding layout report. The layout report is an object in which the layout algorithm stores information about its behavior. For details, see Performing a layout.

4. Attach the grapher to the layout instance.

5. Modify the default settings for the layout parameters, if necessary.

6. Call the performLayout method inside a try block.

7. Read and display information from the layout report.

8. Catch the exceptions.

9. When the layout instance is no longer needed, detach the grapher from it.

Running the sample application that uses the graph layout API

You can use this application as an example to get started with the layout algorithms of the graph layout package.

The example uses the Tree layout, but most of the principles apply to any of the other layouts. The source code of the application is named Sample4.java and it is located at <installdir>/jviews-diagrammer/codefragments/graphlayout/sample4/src/Sample4.java.

To compile and run sample 4:

1. Go to the sample4 directory. On Microsoft® Windows® systems, you must open a Command Prompt window.

2. Set the CLASSPATH variable to the Rogue Wave JViews Diagrammer library and the current directory.

On Microsoft Windows systems	.;<installdir>\jviews-diagrammer\lib\jviews-diagrammer-all.jar;<installdir>\jviews-framework\lib\jviews-framework-all.jar
On UNIX® systems	.:<installdir>/jviews-diagrammer/lib/jviews-diagrammer-all.jar:<installdir>/jviews-framework/lib/jviews-framework-all.jar

3. Compile the application:

javac -d . src/Sample4.java

4. Run the application:

java Sample4

The Sample4.java file contains the following code:

// the JViews Graphic Framework

import ilog.views.*;

// the JViews Graph Layout Framework

import ilog.views.graphlayout.*;

// the JViews Tree Layout

import ilog.views.graphlayout.tree.*;

// the Java AWT package

import java.awt.*;

// the Java Swing package

import javax.swing.*;

public class Sample4

{

public static void main(String[] arg)

{

SwingUtilities.invokeLater(new Runnable() {

public void run() {

// Declare a handle for the layout instance

IlvTreeLayout layout = new IlvTreeLayout();

// Create the grapher instance

IlvGrapher grapher = new IlvGrapher();

// Create the manager view instance

IlvManagerView view = new IlvManagerView(grapher);

// Change view parameters.

view.setBackground(Color.white);

view.setKeepingAspectRatio(true);

// The name of the IVL file containing the graph data

String fileName = "data/Sample.ivl";

// Fill the grapher with nodes and links from a JViews IVL file.

// Alternatively, the nodes and links could be created

// programmatically.

try {

grapher.read(fileName);

} catch (Exception e) {

System.out.println("could not read " + fileName);

return;

}

// A Swing Frame to display

JFrame frame = new JFrame("Layout Sample");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

// Put the manager view inside the Swing Frame and show it.

frame.getContentPane().add(view);

frame.setSize(600, 600);

frame.setVisible(true);

// perform the layout in the AWT thread

performLayout(grapher, view, layout);

}

});

}

/**

* Perform the layout.

private static void performLayout(IlvGrapher grapher, IlvManagerView view,

IlvTreeLayout layout)

{

// Attach the grapher to the layout instance

layout.attach(grapher);

// Change some layout parameters

layout.setFlowDirection(IlvDirection.Bottom);

layout.setGlobalLinkStyle(IlvTreeLayout.ORTHOGONAL_STYLE);

try {

// Perform the layout and get the layout report

IlvGraphLayoutReport layoutReport = layout.performLayout();

int code = layoutReport.getCode();

// Print information from the layout report (optional)

System.out.println("Done in " +

layoutReport.getLayoutTime() +

" millisec., return code = " +

code + " (" +

layoutReport.codeToString(code) + ")");

}

// Catch the exceptions

catch (IlvGraphLayoutException e) {

System.out.println(e.getMessage());

}

finally {

// Fit the view to show the entire graph

view.fitTransformerToContent();

// Redraw the grapher

grapher.reDraw();

}

// Detach the grapher from the layout instance

layout.detach();

}

The sample Java™ application sample 4 produces the following graph.

Output from sample 4