SelectGraphVertices

import vtk.*;
/*
 * Java language example to select edges and vertices from a generated Graph.
 */
public class SelectGraphVertices {

  /**
     * All Java programs require a host class. in addition, 
     * these two instance variables provide access to the 
     * callback data used in this example. 
     */
  vtkGraphLayoutView view;
  vtkAnnotationLink link; 
  /*
     * The following static calls will load the respective 
     * vtkJava interface libraries on first reference to this
     * class. 
     */
  // Loading Native Libraries.
  // Now it works in eclipse without any issues.
  static {
    if (!vtkNativeLibrary.LoadAllNativeLibraries()) {
      for (vtkNativeLibrary lib : vtkNativeLibrary.values()) {
        if (!lib.IsLoaded()) {
          System.out.println(lib.GetLibraryName() + " not loaded");
        }
      }
    }
    vtkNativeLibrary.DisableOutputWindow(null);
  }
  /*
     * primary test driver, creates an instance of this class 
     * and then runs the example function. 
     */
  public static void main(String[] args) {

    SelectGraphVertices me = new SelectGraphVertices();
    me.doit();
  }
  /*
     * doit creates local objects and instantiates instance variables
     */
  public void doit() {
    vtkRandomGraphSource source = new vtkRandomGraphSource();
    source.Update();

    view =  new vtkGraphLayoutView();
    view.AddRepresentationFromInputConnection(source.GetOutputPort());
    /*
         * This was described as vtkRenderedGraphRepresentation in the python example, 
         * but the java type returns it as vtkDataRepresentation. 
         */
    vtkDataRepresentation rep = view.GetRepresentation(0);

    /*
        * The vtkDataRepresentation should already have a vtkAnnotationLink,
        * so we just want to grab it and add an observer with our callback function attached
        * Note that Java callbacks use the this "pointer" to anchor vtk objects used by the callback 
        * to establish references to required vtkobjects. 
        */
    link = rep.GetAnnotationLink();
    link.AddObserver("AnnotationChangedEvent", this,  "selectionCallback");

    view.GetRenderWindow().SetSize(600, 600);
    view.ResetCamera();
    view.Render();
    view.GetInteractor().Start();

  }
  /*
     * The Java callback signature has no parameters. This complicates some
     * vtk processes by eliminating the eventid and user data normally available
     * to C++ logic.
     */
  public void  selectionCallback() {
    // In C++ there is some extra data passed to the callback, but in Python
    // the callback data is lost...

    // There can be two selection nodes, but which one is vertices and which is edges
    // does not seem to be guaranteed...
    System.out.println("in selection callback");

    vtkSelection sel = link.GetCurrentSelection();
    vtkSelectionNode node0 = sel.GetNode(0);
    int node0_field_type = node0.GetFieldType();

    vtkIdTypeArray sel_list0 = (vtkIdTypeArray)(link.GetCurrentSelection().GetNode(0).GetSelectionList());

    vtkSelectionNode node1 = sel.GetNode(1);
    int node1_field_type = node1.GetFieldType();

    vtkIdTypeArray sel_list1 = (vtkIdTypeArray)(link.GetCurrentSelection().GetNode(1).GetSelectionList());

    if (sel_list0.GetNumberOfTuples() > 0) {
      printFieldType(node0_field_type);
      for (int ii = 0; ii < sel_list0.GetNumberOfTuples(); ii++){
        System.out.print( "\t" + sel_list0.GetValue(ii));
      }
      System.out.println(" - on list 0." );
    }
    if (sel_list1.GetNumberOfTuples() > 0) {
      printFieldType(node1_field_type);
      for (int ii = 0; ii < sel_list1.GetNumberOfTuples(); ii++){
        System.out.print( "\t" + sel_list1.GetValue(ii));
      }
      System.out.println(" - on list 1." );
    }
    System.out.println( "- - -");

  }

  public void printFieldType(int field_type) {
    if (field_type == 3) 
      System.out.print("Vertices Selected:");
    else if (field_type == 4)
      System.out.print ("Edges Selected:");
    else
      System.out.print ("Unknown type:");
  }

}