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/*******************************************************************************
* 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;
/**
*
* This class is a partial implementation of IHandler. 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()}.
*
*
* @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.
*
* 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 AbstractHandler in
* org.eclipse.ui.workbench, and clients should be wary of
* overriding this behaviour. If this method is overridden, then the first
* line of the method should be "super.fireHandlerChanged(handlerEvent);".
*
*
* @param handlerEvent
* the event describing changes to this instance. Must not be
* null.
*/
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 true
* @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 null
* @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 true
*/
public boolean isHandled() {
return true;
}
/**
*
* Returns true iff there is one or more IHandlerListeners attached to this
* AbstractHandler.
*
*
* 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 AbstractHandler in
* org.eclipse.ui.workbench, and clients should be wary of
* overriding this behaviour. If this method is overridden, then the return
* value should include "super.hasListeners() ||".
*
*
* @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);
}
}