bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ObservableMapCellLabelProvider.java

/*******************************************************************************
 * Copyright (c) 2006, 2009 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
 *     Brad Reynolds - bug 164247
 *     Brad Reynolds - bug 164134
 *******************************************************************************/

package org.eclipse.jface.databinding.viewers;

import java.util.Set;

import org.eclipse.core.databinding.observable.map.IMapChangeListener;
import org.eclipse.core.databinding.observable.map.IObservableMap;
import org.eclipse.core.databinding.observable.map.MapChangeEvent;
import org.eclipse.jface.viewers.CellLabelProvider;
import org.eclipse.jface.viewers.LabelProviderChangedEvent;
import org.eclipse.jface.viewers.ViewerCell;

/**
 * A label provider based on one or more observable maps that track attributes
 * that this label provider uses for display. The default behavior is to display
 * the first attribute's value. Clients may customize by subclassing and
 * overriding {@link #update(ViewerCell)}.
 * 
 * @since 1.3
 * 
 */
public class ObservableMapCellLabelProvider extends CellLabelProvider {

	private IObservableMap[] attributeMaps;

	private IMapChangeListener mapChangeListener = new IMapChangeListener() {
		public void handleMapChange(MapChangeEvent event) {
			Set affectedElements = event.diff.getChangedKeys();
			LabelProviderChangedEvent newEvent = new LabelProviderChangedEvent(
					ObservableMapCellLabelProvider.this, affectedElements
							.toArray());
			fireLabelProviderChanged(newEvent);
		}
	};

	/**
	 * Creates a new label provider that tracks changes to one attribute.
	 * 
	 * @param attributeMap
	 */
	public ObservableMapCellLabelProvider(IObservableMap attributeMap) {
		this(new IObservableMap[] { attributeMap });
	}

	/**
	 * Creates a new label provider that tracks changes to more than one
	 * attribute. This constructor should be used by subclasses that override
	 * {@link #update(ViewerCell)} and make use of more than one attribute.
	 * 
	 * @param attributeMaps
	 */
	protected ObservableMapCellLabelProvider(IObservableMap[] attributeMaps) {
		System.arraycopy(attributeMaps, 0,
				this.attributeMaps = new IObservableMap[attributeMaps.length],
				0, attributeMaps.length);
		for (int i = 0; i < attributeMaps.length; i++) {
			attributeMaps[i].addMapChangeListener(mapChangeListener);
		}
	}

	public void dispose() {
		for (int i = 0; i < attributeMaps.length; i++) {
			attributeMaps[i].removeMapChangeListener(mapChangeListener);
		}
		super.dispose();
		this.attributeMaps = null;
		this.mapChangeListener = null;
	}

	public void update(ViewerCell cell) {
		Object element = cell.getElement();
		Object value = attributeMaps[0].get(element);
		cell.setText(value == null ? "" : value.toString()); //$NON-NLS-1$
	}

}