| /******************************************************************************* |
| * Copyright (c) 2004, 2008 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.core.commands; |
| |
| import org.eclipse.core.commands.common.EventManager; |
| |
| /** |
| * <p> |
| * This class is a partial implementation of <code>IHandler</code>. This |
| * abstract implementation provides support for handler listeners. You should |
| * subclass from this method unless you want to implement your own listener |
| * support. Subclasses should call |
| * {@link AbstractHandler#fireHandlerChanged(HandlerEvent)}when the handler |
| * changes. Subclasses can also override {@link AbstractHandler#isEnabled()} and |
| * {@link AbstractHandler#isHandled()}. |
| * </p> |
| * |
| * @since 3.1 |
| */ |
| public abstract class AbstractHandler extends EventManager implements IHandler2 { |
| |
| /** |
| * Track this base class enabled state. |
| * |
| * @since 3.4 |
| */ |
| private boolean baseEnabled = true; |
| |
| /** |
| * @see IHandler#addHandlerListener(IHandlerListener) |
| */ |
| public void addHandlerListener(final IHandlerListener handlerListener) { |
| addListenerObject(handlerListener); |
| } |
| |
| /** |
| * The default implementation does nothing. Subclasses who attach listeners |
| * to other objects are encouraged to detach them in this method. |
| * |
| * @see org.eclipse.core.commands.IHandler#dispose() |
| */ |
| public void dispose() { |
| // Do nothing. |
| } |
| |
| /** |
| * Fires an event to all registered listeners describing changes to this |
| * instance. |
| * <p> |
| * Subclasses may extend the definition of this method (i.e., if a different |
| * type of listener can be attached to a subclass). This is used primarily |
| * for support of <code>AbstractHandler</code> in |
| * <code>org.eclipse.ui.workbench</code>, and clients should be wary of |
| * overriding this behaviour. If this method is overridden, then the first |
| * line of the method should be "<code>super.fireHandlerChanged(handlerEvent);</code>". |
| * </p> |
| * |
| * @param handlerEvent |
| * the event describing changes to this instance. Must not be |
| * <code>null</code>. |
| */ |
| protected void fireHandlerChanged(final HandlerEvent handlerEvent) { |
| if (handlerEvent == null) { |
| throw new NullPointerException(); |
| } |
| |
| final Object[] listeners = getListeners(); |
| for (int i = 0; i < listeners.length; i++) { |
| final IHandlerListener listener = (IHandlerListener) listeners[i]; |
| listener.handlerChanged(handlerEvent); |
| } |
| } |
| |
| /** |
| * Whether this handler is capable of executing at this time. Subclasses may |
| * override this method. If clients override this method they should also |
| * consider overriding {@link #setEnabled(Object)} so they can be notified |
| * about framework execution contexts. |
| * |
| * @return <code>true</code> |
| * @see #setEnabled(Object) |
| * @see #setBaseEnabled(boolean) |
| */ |
| public boolean isEnabled() { |
| return baseEnabled; |
| } |
| |
| /** |
| * Allow the default {@link #isEnabled()} to answer our enabled state. It |
| * will fire a HandlerEvent if necessary. If clients use this method they |
| * should also consider overriding {@link #setEnabled(Object)} so they can |
| * be notified about framework execution contexts. |
| * |
| * @param state |
| * the enabled state |
| * @since 3.4 |
| */ |
| protected void setBaseEnabled(boolean state) { |
| if (baseEnabled == state) { |
| return; |
| } |
| baseEnabled = state; |
| fireHandlerChanged(new HandlerEvent(this, true, false)); |
| } |
| |
| /** |
| * Called by the framework to allow the handler to update its enabled state |
| * by extracting the same information available at execution time. Clients |
| * may override if they need to extract information from the application |
| * context. |
| * |
| * @param evaluationContext |
| * the application context. May be <code>null</code> |
| * @since 3.4 |
| * @see #setBaseEnabled(boolean) |
| */ |
| public void setEnabled(Object evaluationContext) { |
| } |
| |
| /** |
| * Whether this handler is capable of handling delegated responsibilities at |
| * this time. Subclasses may override this method. |
| * |
| * @return <code>true</code> |
| */ |
| public boolean isHandled() { |
| return true; |
| } |
| |
| /** |
| * <p> |
| * Returns true iff there is one or more IHandlerListeners attached to this |
| * AbstractHandler. |
| * </p> |
| * <p> |
| * Subclasses may extend the definition of this method (i.e., if a different |
| * type of listener can be attached to a subclass). This is used primarily |
| * for support of <code>AbstractHandler</code> in |
| * <code>org.eclipse.ui.workbench</code>, and clients should be wary of |
| * overriding this behaviour. If this method is overridden, then the return |
| * value should include "<code>super.hasListeners() ||</code>". |
| * </p> |
| * |
| * @return true iff there is one or more IHandlerListeners attached to this |
| * AbstractHandler |
| */ |
| protected boolean hasListeners() { |
| return isListenerAttached(); |
| } |
| |
| /** |
| * @see IHandler#removeHandlerListener(IHandlerListener) |
| */ |
| public void removeHandlerListener(final IHandlerListener handlerListener) { |
| removeListenerObject(handlerListener); |
| } |
| } |