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Graphical Modeling Framework/Recipes

< Graphical Modeling Framework
Revision as of 11:26, 22 February 2008 by (Talk | contribs) (Recipe: HowTo reorder children in a GMF compartment with Drag & Drop)

Recipe: HowTo reorder children in a GMF compartment with Drag & Drop

Problem: You have created a node class which can contain other nodes. E.g. a class bookshelf that contains objects of the class book. Therefore you created a compartment. After adding books to the bookshelf in your editor, you want to rearrange the books by drag & drop. But it doesn't work...


In the xxxCompartmentEditPart class rewrite the createFigure() method:

	public IFigure createFigure() {
		ResizableCompartmentFigure rcf = (ResizableCompartmentFigure) super.createFigure();
		FlowLayout layout = new FlowLayout();


		return rcf;

In the createDefaultEditPolicies() method of the xxxCompartmentEditPart class add an EditPolicy:

installEditPolicy(EditPolicy.LAYOUT_ROLE, new CompartmentEditPolicy(;

Note: has to be the EStructuralFeature of the EList Attribute that contains the Objects which should be reordered.

Use the classes CompartmentEditPolicy and CompartmentRepositionEObjectCommand:

public class CompartmentEditPolicy
extends org.eclipse.gef.editpolicies.FlowLayoutEditPolicy

	private EStructuralFeature feature = null;

	protected Command createAddCommand(EditPart child, EditPart after) {
		int index = getHost().getChildren().indexOf(after);
		TransactionalEditingDomain editingDomain = ((IGraphicalEditPart) getHost()).getEditingDomain();
		AddCommand command = new AddCommand(editingDomain, new EObjectAdapter((View)getHost().getModel()),
				new EObjectAdapter((View)child.getModel()), index);
		return new ICommandProxy(command);

	protected EditPolicy createChildEditPolicy(EditPart child) {
		ResizableEditPolicyEx policy = new ResizableEditPolicyEx();
		return policy;

	protected Command createMoveChildCommand(EditPart child, EditPart after) {	

		int newIndex;
		int displacement;

		int childIndex = getHost().getChildren().indexOf(child);
		int afterIndex = getHost().getChildren().indexOf(after);	

		if(afterIndex == -1) {
			newIndex = getHost().getChildren().size()-1;			
			displacement = newIndex - childIndex;
		} else {		
			newIndex = afterIndex;
			displacement = afterIndex - childIndex;
			if (childIndex <= afterIndex) {

		TransactionalEditingDomain editingDomain = ((IGraphicalEditPart) getHost()).getEditingDomain();

		RepositionEObjectCommand command = new CompartmentRepositionEObjectCommand(child, editingDomain, "", 
				displacement, newIndex);	

		//TODO ev. reintroduce target feedback (actual problem: line is not deleted after dropping)

		return new ICommandProxy(command);

	protected Command getCreateCommand(CreateRequest request) {
		return null;

	protected Command getDeleteDependantCommand(Request request) {
		return null;

	protected Command getOrphanChildrenCommand(Request request) {
		return null;

	 * @param feature has to be an EList
	public CompartmentEditPolicy(EStructuralFeature feature) {
		this.feature = feature;

public class CompartmentRepositionEObjectCommand extends RepositionEObjectCommand {

	EditPart childToMove = null;
	int newIndex = 0;
	public CompartmentRepositionEObjectCommand(
			TransactionalEditingDomain editingDomain, String label,
			EList elements, EObject element, int displacement) {
		super(editingDomain, label, elements, element, displacement);
	public CompartmentRepositionEObjectCommand(EditPart childToMove,
			TransactionalEditingDomain editingDomain, String label,
			EList elements, EObject element, int displacement, int newIndex) {
		super(editingDomain, label, elements, element, displacement);
		this.childToMove = childToMove;
		this.newIndex = newIndex;
	public CommandResult doExecuteWithResult(
			IProgressMonitor progressMonitor, IAdaptable info)
			throws ExecutionException {
		CommandResult rs = super.doExecuteWithResult(progressMonitor, info);
		EditPart compartment = childToMove.getParent(); 
		ViewUtil.repositionChildAt((View)compartment.getModel(), (View)childToMove.getModel(), newIndex);
		return rs;

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