GraphicalCommandHandler.java example

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/*****************************************************************************
 * Copyright (c) 2010 CEA LIST.
 *
 * 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Patrick Tessier (CEA LIST) Patrick.tessier@cea.fr - Initial API and implementation
 *
 *****************************************************************************/
package org.eclipse.papyrus.uml.diagram.common.handlers;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.emf.transaction.TransactionalEditingDomain;
import org.eclipse.gef.commands.Command;
import org.eclipse.gmf.runtime.diagram.ui.editparts.IGraphicalEditPart;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.papyrus.commands.wrappers.GEFtoEMFCommandWrapper;
import org.eclipse.papyrus.infra.core.services.ServiceException;
import org.eclipse.papyrus.infra.core.utils.ServiceUtilsForActionHandlers;
import org.eclipse.papyrus.uml.diagram.common.Activator;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;

/**
 * This abstract command handler: - calculates the current selection -
 * calculates the visibility and enablement based on command executability -
 * executes the command in Papyrus command stack
 * 
 */
public abstract class GraphicalCommandHandler extends AbstractHandler {

	protected abstract Command getCommand() throws ExecutionException;

	/**
	 * Iterate over current selection and build a list of the {@link IGraphicalEditPart} contained in the selection.
	 * 
	 * @return the currently selected {@link IGraphicalEditPart}
	 */
	protected List<IGraphicalEditPart> getSelectedElements() {
		List<IGraphicalEditPart> editparts = new ArrayList<IGraphicalEditPart>();

		// Get current selection
		IWorkbenchWindow activeWorkbenchWindow = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
		Object selection = (activeWorkbenchWindow != null) ? activeWorkbenchWindow.getSelectionService().getSelection() : null;

		// Treat non-null selected object (try to adapt and return EObject)
		if(selection != null) {

			if(selection instanceof IStructuredSelection) {

				IStructuredSelection structuredSelection = (IStructuredSelection)selection;

				Iterator<?> it = structuredSelection.iterator();
				while(it.hasNext()) {
					Object object = it.next();
					if(object instanceof IGraphicalEditPart) {
						editparts.add((IGraphicalEditPart)object);
					}
				}

			} else if(selection instanceof IGraphicalEditPart) {
				editparts.add((IGraphicalEditPart)selection);
			}
		}

		return editparts;
	}

	/**
	 * 
	 * @see org.eclipse.core.commands.AbstractHandler#execute(org.eclipse.core.commands.ExecutionEvent)
	 * 
	 * @param event
	 * @return null
	 * @throws ExecutionException
	 */
	public Object execute(ExecutionEvent event) throws ExecutionException {

		TransactionalEditingDomain editingDomain = getEditingDomain();
		Command command = getCommand();
		if(editingDomain != null && command != null) {
			editingDomain.getCommandStack().execute(new GEFtoEMFCommandWrapper(command));
		}

		return null;
	}

	/**
	 * 
	 * @see org.eclipse.core.commands.AbstractHandler#isEnabled()
	 * 
	 * @return true is the command can be executed
	 */
	@Override
	public boolean isEnabled() {

		try {
			Command command = getCommand();
			if(command != null && command.canExecute()) {
				return true;
			}
		} catch (ExecutionException e) {
			Activator.log.error(e);
		}

		return false;
	}

	/**
	 * 
	 * @return true if the command can be executed
	 */
	public boolean isVisible() {
		return isEnabled();
	}

	/**
	 * Retrieves the TransactionalEditingDomain
	 * 
	 * @return the editing domain (can be null)
	 */
	protected TransactionalEditingDomain getEditingDomain() {
		ServiceUtilsForActionHandlers serviceUtils = new ServiceUtilsForActionHandlers();
		TransactionalEditingDomain editingDomain = null;
		try {
			editingDomain = serviceUtils.getTransactionalEditingDomain();

		} catch (ServiceException e) {
			Activator.log.error(e);
		}

		return editingDomain;
	}
}