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/*******************************************************************************
 * Copyright (c) 2005, 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.jface.commands;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.eclipse.core.commands.IStateListener;
import org.eclipse.core.commands.State;
import org.eclipse.jface.menus.IMenuStateIds;

/**
 * 

* A piece of boolean state grouped with other boolean states. Of these states, * only one may have a value of {@link Boolean#TRUE} at any given point in time. * The values of all other states must be {@link Boolean#FALSE}. *

*

* If this state is registered using {@link IMenuStateIds#STYLE}, then it will * control the presentation of the command if displayed in the menus, tool bars * or status line. *

*

* Clients may instantiate or extend this interface. *

* * @since 1.0 */ public class RadioState extends ToggleState { /** * The manager of radio groups within the application. This ensures that * only one member of a radio group is active at any one time, and tracks * group memberships. */ private static final class RadioStateManager { /** * A group of radio states with the same identifier. */ private static final class RadioGroup implements IStateListener { /** * The active state. If there is no active state, then this value is * null. */ private RadioState active = null; /** * The current members in this group. If there are no members, then * this value is nlistenerull. */ private Set members = null; /** * Activates a memeber. This checks to see if there are any other * active members. If there are, they are deactivated. * * @param state * The state that should become active; must not be * null. */ private final void activateMember(final RadioState state) { if (active!=null && active != state) { active.setValue(Boolean.FALSE); } active = state; } /** * Adds a member to this radio group. If the state being added is * active, then it replaces the currently active group memeber as * the active state. * * @param state * The state to add; must not be null. */ private final void addMember(final RadioState state) { if (members == null) { members = new HashSet(5); } members.add(state); state.addListener(this); final Object value = state.getValue(); if (value instanceof Boolean) { if (((Boolean) value).booleanValue()) { activateMember(state); } } } public final void handleStateChange(final State state, final Object oldValue) { final Object newValue = state.getValue(); if (newValue instanceof Boolean) { if (((Boolean) newValue).booleanValue()) { activateMember((RadioState) state); } } } /** * Removes a member from this radio group. If the state was the * active state, then there will be no active state. * * @param state * The state to remove; must not be null. */ private final void removeMember(final RadioState state) { state.removeListener(this); if (active == state) { active = null; } if (members == null) { return; } members.remove(state); } } /** * The map of radio states indexed by identifier (String). * The radio states is either a single RadioState * instance or a Collection of RadioState * instances. */ private static Map radioStatesById = null; /** * Activates a particular state within a given group. * * @param identifier * The identifier of the group to which the state belongs; * must not be null. * @param state * The state to activate; must not be null. */ private static final void activateGroup(final String identifier, final RadioState state) { if (radioStatesById == null) { return; } final Object currentValue = radioStatesById.get(identifier); if (currentValue instanceof RadioGroup) { final RadioGroup radioGroup = (RadioGroup) currentValue; radioGroup.activateMember(state); } } /** * Registers a piece of state with the radio manager. * * @param identifier * The identifier of the radio group; must not be * null. * @param state * The state to register; must not be null. */ private static final void registerState(final String identifier, final RadioState state) { if (radioStatesById == null) { radioStatesById = new HashMap(); } final Object currentValue = radioStatesById.get(identifier); final RadioGroup radioGroup; if (currentValue instanceof RadioGroup) { radioGroup = (RadioGroup) currentValue; } else { radioGroup = new RadioGroup(); radioStatesById.put(identifier, radioGroup); } radioGroup.addMember(state); } /** * Unregisters a piece of state from the radio manager. * * @param identifier * The identifier of the radio group; must not be * null. * @param state * The state to unregister; must not be null. */ private static final void unregisterState(final String identifier, final RadioState state) { if (radioStatesById == null) { return; } final Object currentValue = radioStatesById.get(identifier); if (currentValue instanceof RadioGroup) { final RadioGroup radioGroup = (RadioGroup) currentValue; radioGroup.removeMember(state); } } } /** * The identifier of the radio group to which this state belongs. This value * may be null if this state doesn't really belong to a group * (yet). */ private String radioGroupIdentifier = null; /** * Unregisters this state from the manager, which detaches the listeners. */ public void dispose() { setRadioGroupIdentifier(null); } /** * Sets the identifier of the radio group for this piece of state. If the * identifier is cleared, then the state is unregistered. * * @param identifier * The identifier of the radio group for this state; may be * null if the identifier is being cleared. * */ public final void setRadioGroupIdentifier(final String identifier) { if (identifier == null) { RadioStateManager.unregisterState(radioGroupIdentifier, this); radioGroupIdentifier = null; } else { radioGroupIdentifier = identifier; RadioStateManager.registerState(identifier, this); } } /** * Sets the value for this object. This notifies the radio state manager of * the change. * * @param value * The new value; should be a Boolean. */ public void setValue(final Object value) { if (!(value instanceof Boolean)) { throw new IllegalArgumentException( "RadioState takes a Boolean as a value"); //$NON-NLS-1$ } if (((Boolean) value).booleanValue() && (radioGroupIdentifier != null)) { RadioStateManager.activateGroup(radioGroupIdentifier, this); } super.setValue(value); } }




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