| /******************************************************************************* |
| * Copyright (c) 2004, 2005 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; |
| |
| |
| /** |
| * A handler is the pluggable piece of a command that handles execution. Each |
| * command can have zero or more handlers associated with it (in general), of |
| * which only one will be active at any given moment in time. When the command |
| * is asked to execute, it will simply pass that request on to its active |
| * handler, if any. |
| * |
| * @see AbstractHandler |
| * @since 3.1 |
| */ |
| public interface IHandler { |
| |
| /** |
| * Registers an instance of <code>IHandlerListener</code> to listen for |
| * changes to properties of this instance. |
| * |
| * @param handlerListener |
| * the instance to register. Must not be <code>null</code>. If |
| * an attempt is made to register an instance which is already |
| * registered with this instance, no operation is performed. |
| */ |
| void addHandlerListener(IHandlerListener handlerListener); |
| |
| /** |
| * Disposes of this handler. This method is run once when the object is no |
| * longer referenced. This can be used as an opportunity to unhook listeners |
| * from other objects. |
| */ |
| public void dispose(); |
| |
| /** |
| * Executes with the map of parameter values by name. |
| * |
| * @param event |
| * An event containing all the information about the current |
| * state of the application; must not be <code>null</code>. |
| * @return the result of the execution. Reserved for future use, must be |
| * <code>null</code>. |
| * @throws ExecutionException |
| * if an exception occurred during execution. |
| */ |
| Object execute(ExecutionEvent event) throws ExecutionException; |
| |
| /** |
| * Returns whether this handler is capable of executing at this moment in |
| * time. |
| * |
| * @return <code>true</code> if the command is enabled; <code>false</code> |
| * otherwise. |
| */ |
| public boolean isEnabled(); |
| |
| /** |
| * Returns whether this handler is really capable of handling delegation. In |
| * the case of a handler that is a composition of other handlers, this reply |
| * is intended to indicate whether the handler is truly capable of receiving |
| * delegated responsibilities at this time. |
| * |
| * @return <code>true</code> if the handler is handled; <code>false</code> |
| * otherwise. |
| */ |
| public boolean isHandled(); |
| |
| /** |
| * Unregisters an instance of <code>IHandlerListener</code> listening for |
| * changes to properties of this instance. |
| * |
| * @param handlerListener |
| * the instance to unregister. Must not be <code>null</code>. |
| * If an attempt is made to unregister an instance which is not |
| * already registered with this instance, no operation is |
| * performed. |
| */ |
| void removeHandlerListener(IHandlerListener handlerListener); |
| } |