1 /******************************************************************************* 2 * Copyright (c) 2005, 2015 IBM Corporation and others. 3 * 4 * This program and the accompanying materials 5 * are made available under the terms of the Eclipse Public License 2.0 6 * which accompanies this distribution, and is available at 7 * https://www.eclipse.org/legal/epl-2.0/ 8 * 9 * SPDX-License-Identifier: EPL-2.0 10 * 11 * Contributors: 12 * IBM Corporation - initial API and implementation 13 *******************************************************************************/ 14 15 package org.eclipse.core.commands; 16 17 import java.util.HashMap; 18 import java.util.Map; 19 import java.util.Set; 20 21 /** 22 * <p> 23 * An abstract implementation of {@link IObjectWithState}. This provides basic 24 * handling for adding and remove state. When state is added, the handler 25 * attaches itself as a listener and fire a handleStateChange event to notify 26 * this handler. When state is removed, the handler removes itself as a 27 * listener. 28 * </p> 29 * <p> 30 * Clients may extend this class. 31 * </p> 32 * 33 * @since 3.2 34 */ 35 public abstract class AbstractHandlerWithState extends AbstractHandler implements IObjectWithState, IStateListener { 36 37 /** 38 * The map of states currently held by this handler. If this handler has no 39 * state (generally, when inactive), then this will be <code>null</code>. 40 */ 41 private Map<String, State> states; 42 43 private static final String[] EMPTY = new String[0]; 44 45 /** 46 * <p> 47 * Adds a state to this handler. This will add this handler as a listener to 48 * the state, and then fire a handleStateChange so that the handler can 49 * respond to the incoming state. 50 * </p> 51 * <p> 52 * Clients may extend this method, but they should call this super method 53 * first before doing anything else. 54 * </p> 55 * 56 * @param stateId 57 * The identifier indicating the type of state being added; must 58 * not be <code>null</code>. 59 * @param state 60 * The state to add; must not be <code>null</code>. 61 */ 62 @Override addState(final String stateId, final State state)63 public void addState(final String stateId, final State state) { 64 if (state == null) { 65 throw new NullPointerException("Cannot add a null state"); //$NON-NLS-1$ 66 } 67 68 if (states == null) { 69 states = new HashMap<>(3); 70 } 71 states.put(stateId, state); 72 state.addListener(this); 73 handleStateChange(state, null); 74 } 75 76 @Override getState(final String stateId)77 public final State getState(final String stateId) { 78 if ((states == null) || (states.isEmpty())) { 79 return null; 80 } 81 82 return states.get(stateId); 83 } 84 85 @Override getStateIds()86 public final String[] getStateIds() { 87 if ((states == null) || (states.isEmpty())) { 88 return EMPTY; 89 } 90 91 final Set<String> stateIds = states.keySet(); 92 return stateIds.toArray(new String[stateIds.size()]); 93 } 94 95 /** 96 * <p> 97 * Removes a state from this handler. This will remove this handler as a 98 * listener to the state. No event is fired to notify the handler of this 99 * change. 100 * </p> 101 * <p> 102 * Clients may extend this method, but they should call this super method 103 * first before doing anything else. 104 * </p> 105 * 106 * @param stateId 107 * The identifier of the state to remove; must not be 108 * <code>null</code>. 109 */ 110 @Override removeState(final String stateId)111 public void removeState(final String stateId) { 112 if (stateId == null) { 113 throw new NullPointerException("Cannot remove a null state"); //$NON-NLS-1$ 114 } 115 if (states == null) { 116 return; 117 } 118 final State state = states.get(stateId); 119 if (state != null) { 120 state.removeListener(this); 121 if (states != null) { 122 states.remove(stateId); 123 if (states.isEmpty()) { 124 states = null; 125 } 126 } 127 } 128 } 129 } 130