org.eclipse.jface.databinding.viewers.ObservableMapCellLabelProvider.java Source code

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Here is the source code for org.eclipse.jface.databinding.viewers.ObservableMapCellLabelProvider.java

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/*******************************************************************************
 * Copyright (c) 2006, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Brad Reynolds - bugs 164247, 164134
 *     Matthew Hall - bug 302860
 *******************************************************************************/

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 {

    /**
     * Observable maps typically mapping from viewer elements to label values.
     * Subclasses may use these maps to provide custom labels.
     *
     * @since 1.4
     */
    protected IObservableMap<Object, Object>[] attributeMaps;

    private IMapChangeListener<Object, Object> mapChangeListener = new IMapChangeListener<Object, Object>() {
        @Override
        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 attribute map to track
     */
    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 attribute maps to track
     */
    @SuppressWarnings("unchecked")
    protected ObservableMapCellLabelProvider(IObservableMap<?, ?>[] attributeMaps) {
        System.arraycopy(attributeMaps, 0, this.attributeMaps = new IObservableMap[attributeMaps.length], 0,
                attributeMaps.length);
        for (IObservableMap<?, ?> attributeMap : attributeMaps) {
            attributeMap.addMapChangeListener(mapChangeListener);
        }
    }

    @Override
    public void dispose() {
        for (IObservableMap<?, ?> attributeMap : attributeMaps) {
            attributeMap.removeMapChangeListener(mapChangeListener);
        }
        super.dispose();
        this.attributeMaps = null;
        this.mapChangeListener = null;
    }

    /**
     * Updates the label of the cell with the value for the cell element. Note:
     * The value for the first map is always used, for all columns.
     *
     * @param cell
     *            The cell to be updated.
     */
    @Override
    public void update(ViewerCell cell) {
        Object element = cell.getElement();
        // Always use the value from the first map
        Object value = attributeMaps[0].get(element);
        cell.setText(value == null ? "" : value.toString()); //$NON-NLS-1$
    }
}