| /******************************************************************************* |
| * Copyright (c) 2007 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.eclipse.ui.internal; |
| |
| import org.eclipse.core.expressions.Expression; |
| import org.eclipse.jface.util.IPropertyChangeListener; |
| import org.eclipse.jface.util.PropertyChangeEvent; |
| import org.eclipse.ui.PlatformUI; |
| import org.eclipse.ui.services.IEvaluationReference; |
| import org.eclipse.ui.services.IEvaluationService; |
| |
| /** |
| * This internal class serves as a foundation for any handler that would like |
| * its enabled state controlled by core expressions and the IEvaluationService. |
| * |
| * @since 3.3 |
| */ |
| public abstract class AbstractEvaluationHandler extends AbstractEnabledHandler { |
| private final static String PROP_ENABLED = "enabled"; //$NON-NLS-1$ |
| private IEvaluationService evaluationService; |
| private IPropertyChangeListener enablementListener; |
| private IEvaluationReference enablementRef; |
| |
| protected IEvaluationService getEvaluationService() { |
| if (evaluationService == null) { |
| evaluationService = (IEvaluationService) PlatformUI.getWorkbench() |
| .getService(IEvaluationService.class); |
| } |
| return evaluationService; |
| } |
| |
| protected void registerEnablement() { |
| enablementRef = getEvaluationService().addEvaluationListener( |
| getEnabledWhenExpression(), getEnablementListener(), |
| PROP_ENABLED); |
| } |
| |
| protected abstract Expression getEnabledWhenExpression(); |
| |
| /** |
| * @return |
| */ |
| private IPropertyChangeListener getEnablementListener() { |
| if (enablementListener == null) { |
| enablementListener = new IPropertyChangeListener() { |
| public void propertyChange(PropertyChangeEvent event) { |
| if (event.getProperty() == PROP_ENABLED) { |
| if (event.getNewValue() instanceof Boolean) { |
| setEnabled(((Boolean) event.getNewValue()) |
| .booleanValue()); |
| } else { |
| setEnabled(false); |
| } |
| } |
| } |
| }; |
| } |
| return enablementListener; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.eclipse.core.commands.AbstractHandler#dispose() |
| */ |
| public void dispose() { |
| if (enablementRef != null) { |
| evaluationService.removeEvaluationListener(enablementRef); |
| enablementRef = null; |
| enablementListener = null; |
| evaluationService = null; |
| } |
| super.dispose(); |
| } |
| } |