Question

I have implemented a GEF editor for a graph-like EMF model, with a remove command for a certain type of node in the graph. I think I’ve done all the necessary steps in order to make this set up work (vainolo‘s blog has been a great help).

However, when I’m deleting a model element, the view doesn’t get refreshed, i.e., the figure for the model element isn’t removed from the editor view, and I have no idea why. I’d be extremely grateful if somebody could have a look at my sources and point me to any problems (and possibly solutions :)). Many thanks in advance!

Below are what I think are the important classes for this issue. Please do let me know should I add further code/edit the code, etc. (I’ve left out code that I thought doesn’t help, e.g., getters and setters, class variables). Thanks!

DiagramEditPart

public class DiagramEditPart extends AbstractGraphicalEditPart {

    public DiagramEditPart(Diagram model) {
        this.setModel(model);
        adapter = new DiagramAdapter();
    }

    @Override protected IFigure createFigure() {
        Figure figure = new FreeformLayer();
        return figure;
      }

      @Override protected void createEditPolicies() {
        installEditPolicy(EditPolicy.LAYOUT_ROLE, new DiagramXYLayoutPolicy());
      }

      @Override protected List<EObject> getModelChildren() {
          List<EObject> allModelObjects = new ArrayList<EObject>();
          if (((Diagram) getModel()).getMyNodes() != null)
          allModelObjects.addAll(((Diagram) getModel()).getMyNodes());
          return allModelObjects;
      }

      @Override public void activate() {
          if(!isActive()) {
              ((Diagram) getModel()).eAdapters().add(adapter);
          }
          super.activate();
      }


      @Override public void deactivate() {
          if(isActive()) {
              ((Diagram) getModel()).eAdapters().remove(adapter);
          }
          super.deactivate();
      }

    public class DiagramAdapter implements Adapter {

          @Override public void notifyChanged(Notification notification) {
              switch (notification.getEventType()) {
            case Notification.REMOVE: refreshChildren();
                break;
            default:
                break;
            }
          }

          @Override public Notifier getTarget() {
              return (Diagram) getModel();
          }

          @Override public void setTarget(Notifier newTarget) {
              // Do nothing.
          }

          @Override public boolean isAdapterForType(Object type) {
              return type.equals(Diagram.class);
          } 

      }

}

MyNodeEditPart

public class MyNodeEditPart extends AbstractGraphicalEditPart {

    public MyNodeEditPart(MyNode model) {
         this.setModel(model);
         adapter = new MyNodeAdapter();
    }

    @Override protected IFigure createFigure() {
        return new MyNodeFigure();
    }

    @Override protected void createEditPolicies() {
        installEditPolicy(EditPolicy.COMPONENT_ROLE, new MyNodeComponentEditPolicy());
    }

    @Override protected void refreshVisuals() {
        MyNodeFigure figure = (MyNodeFigure) getFigure();
        DiagramEditPart parent = (DiagramEditPart) getParent();
        Dimension labelSize = figure.getLabel().getPreferredSize();
        Rectangle layout = new Rectangle((getParent().getChildren().indexOf(this) * 50), 
                (getParent().getChildren().indexOf(this) * 50), (labelSize.width + 20), 
                (labelSize.height + 20));
        parent.setLayoutConstraint(this, figure, layout);
    }

    public List<Edge> getModelSourceConnections() {
        if ((MyNode) getModel() != null && ((MyNode) getModel()).getDiagram() != null) {
            ArrayList<Edge> sourceConnections = new ArrayList<Edge>();
            for (Edge edge : ((MyNode) getModel()).getDiagram().getOutEdges(((MyNode) getModel()).getId())) {
                sourceConnections.add(edge);
            }
            return sourceConnections;
        }
        return null;
    }

    // + the same method for targetconnections

    @Override public void activate() {
        if (!isActive()) {
            ((MyNode) getModel()).eAdapters().add(adapter);
        }
        super.activate();
    }

    @Override public void deactivate() {
        if (isActive()) {
            ((MyNode) getModel()).eAdapters().remove(adapter);
        }
        super.deactivate();
    }

    public class MyNodeAdapter implements Adapter {

        @Override
        public void notifyChanged(Notification notification) {
            refreshVisuals();
        }

        @Override
        public Notifier getTarget() {
            return (MyNode) getModel();
        }

        @Override
        public void setTarget(Notifier newTarget) {
            // Do nothing
        }

        @Override
        public boolean isAdapterForType(Object type) {
            return type.equals(MyNode.class);
        }

    }

}

MyNodeComponentEditPolicy

public class MyNodeComponentEditPolicy extends ComponentEditPolicy {

    @Override
    protected Command createDeleteCommand(GroupRequest deleteRequest) {
        DeleteMyNodeCommand nodeDeleteCommand = new DeleteMyNodeCommand((MyNode) getHost().getModel());
        return nodeDeleteCommand;
    }

}

DeleteMyNodeCommand

public class DeleteMyNodeCommand extends Command {

    public DeleteMyNodeCommand(MyNode model) {
        this.node = model;
        this.graph = node.getDiagram();
    }

    @Override public void execute() {
        getMyNode().setDiagram(null);
        System.out.println("Is the model still present in the graph? " + getGraph().getMyNodes().contains(getMyNode())); 
            // Returns false, i.e., graph doesn't contain model object at this point!
    }

    @Override public void undo() {
        getMyNode().setDiagram(getGraph());
    }

}

---

EDIT

Re execc’s comment: Yes, refreshChildren() is being called. I’ve tested this by overriding it and adding a simple System.err line, which is being displayed on the console on deletion of a node:

@Override
public void refreshChildren() {
    super.refreshChildren();
    System.err.println("refreshChildren() IS being called!");
}

---

EDIT 2

The funny (well…) thing is, when I close the editor and persist the model, then re-open the same file, the node isn’t painted anymore, and is not present in the model. But what does this mean? Am I working on a stale model? Or is refreshing/getting the model children not working properly?

---

EDIT 3

I’ve just found a peculiar thing, which might explain the isues I have? In the getModelChildren() method I call allModelObjects.addAll(((Diagram) getModel()).getMyNodes());, and getMyNodes() returns an unmodifiable EList. I found out when I tried to do something along the lines of ((Diagram) getModel()).getMyNodes().remove(getMyNode()) in the delete command, and it threw an UnsupportedOperationException… Hm.

---

EDIT 4

Er, somebody kill me please?
I’ve double-checked whether I’m handling the same Diagram object at all times, and while doing this I stumbled across a very embarassing thing:

The getModelChildren() method in DiagramEditPart in the last version read approx. like this:

@Override protected List<EObject> getModelChildren() {
    List<EObject> allModelObjects = new ArrayList<EObject>();
    EList<MyNode> nodes = ((Diagram) getModel()).getMyNodes();
    for (MyNode node : nodes) {
        if (node.getDiagram() != null); // ### D'Uh! ###
            allModelObjects.add(node);
    }
    return allModelObjects;
 }

I’d like to apologize for stealing everyone’s time! Your suggestions were very helpful, and indeed helped my to finally track down the bug!

I’ve also learned a number of lessons, amongst them: Always paste the original code, over-simplifaction may cloak your bugs! And I’ve learned a lot about EMF, Adapter, and GEF. Still:

Answer 1

There is one semi-colon too many in line 5 of the following part of the code, namely after the if statement: if (node.getDiagram() != null);:

1   @Override protected List<EObject> getModelChildren() {
2       List<EObject> allModelObjects = new ArrayList<EObject>();
3       EList<MyNode> nodes = ((Diagram) getModel()).getMyNodes();
4       for (MyNode node : nodes) {
5           if (node.getDiagram() != null); 
6               allModelObjects.add(node);
7       }
8       return allModelObjects;
9    }