ResourceTransferDragAdapter.java

/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.rubypeople.rdt.internal.ui.packageview;

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

import org.eclipse.core.resources.IResource;

import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.Transfer;

import org.eclipse.jface.util.Assert;
import org.eclipse.jface.util.TransferDragSourceListener;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.ui.part.ResourceTransfer;

/**
 * A drag adapter that transfers the current selection as </code> IResource</code>.
 * Only those elements in the selection are part of the transfer which can be
 * converted into an <code>IResource </code>.
 */
public class ResourceTransferDragAdapter extends DragSourceAdapter implements
		TransferDragSourceListener {

	private ISelectionProvider fProvider;

	/**
	 * Creates a new ResourceTransferDragAdapter for the given selection
	 * provider.
	 * 
	 * @param provider
	 *            the selection provider to access the viewer's selection
	 */
	public ResourceTransferDragAdapter(ISelectionProvider provider) {
		fProvider = provider;
		Assert.isNotNull(fProvider);
	}

	public Transfer getTransfer() {
		return ResourceTransfer.getInstance();
	}

	public void dragStart(DragSourceEvent event) {
		event.doit = convertSelection().size() > 0;
	}

	public void dragSetData(DragSourceEvent event) {
		List resources = convertSelection();
		event.data = resources.toArray(new IResource[resources.size()]);
	}

	public void dragFinished(DragSourceEvent event) {
		if (!event.doit)
			return;
	}

	private List convertSelection() {
		ISelection s = fProvider.getSelection();
		if (!(s instanceof IStructuredSelection))
			return Collections.EMPTY_LIST;
		IStructuredSelection selection = (IStructuredSelection) s;
		List result = new ArrayList(selection.size());
		for (Iterator iter = selection.iterator(); iter.hasNext();) {
			Object element = iter.next();
			if (element instanceof IResource) {
				result.add(element);
			}
		}
		return result;
	}
}