ActionHandler.java

1: /*******************************************************************************
   2:  * Copyright (c) 2004, 2006 IBM Corporation and others.
   3:  * All rights reserved. This program and the accompanying materials
   4:  * are made available under the terms of the Eclipse Public License v1.0
   5:  * which accompanies this distribution, and is available at
   6:  * http://www.eclipse.org/legal/epl-v10.html
   7:  *
   8:  * Contributors:
   9:  *     IBM Corporation - initial API and implementation
  10:  *******************************************************************************/
  11: package org.eclipse.jface.commands;
  12:
  13: import org.eclipse.core.commands.AbstractHandler;
  14: import org.eclipse.core.commands.ExecutionEvent;
  15: import org.eclipse.core.commands.ExecutionException;
  16: import org.eclipse.core.commands.HandlerEvent;
  17: import org.eclipse.core.commands.IHandlerListener;
  18: import org.eclipse.jface.action.IAction;
  19: import org.eclipse.jface.util.IPropertyChangeListener;
  20: import org.eclipse.jface.util.PropertyChangeEvent;
  21: import org.eclipse.swt.widgets.Event;
  22:
  23: /**
  24:  * <p>
  25:  * This class adapts instances of <code>IAction</code> to
  26:  * <code>IHandler</code>.
  27:  * </p>
  28:  *
  29:  * @since 3.1
  30:  */
  31:   public final class ActionHandler extends AbstractHandler {
  32:
  33:    /**
  34:     * The wrapped action. This value is never <code>null</code>.
  35:     */
  36:    private final IAction action;
  37:
  38:    /**
  39:     * The property change listener hooked on to the action. This is initialized
  40:     * when the first listener is attached to this handler, and is removed when
  41:     * the handler is disposed or the last listener is removed.
  42:     */
  43:    private IPropertyChangeListener propertyChangeListener;
  44:
  45:    /**
  46:     * Creates a new instance of this class given an instance of
  47:     * <code>IAction</code>.
  48:     *
  49:     * @param action
  50:     *            the action. Must not be <code>null</code>.
  51:     */
  52:       public ActionHandler(final IAction action) {
  53:           if (action == null) {
  54:            throw new NullPointerException();
  55:        }
  56:
  57:        this.action = action;
  58:    }
  59:
  60:       public final void addHandlerListener(final IHandlerListener handlerListener) {
  61:           if (!hasListeners()) {
  62:            attachListener();
  63:        }
  64:
  65:        super.addHandlerListener(handlerListener);
  66:    }
  67:
  68:    /**
  69:     * When a listener is attached to this handler, then this registers a
  70:     * listener with the underlying action.
  71:     *
  72:     * @since 3.1
  73:     */
  74:       private final void attachListener() {
  75:           if (propertyChangeListener == null) {
  76:               propertyChangeListener = new IPropertyChangeListener() {
  77:                public final void propertyChange(
  78:                           final PropertyChangeEvent propertyChangeEvent) {
  79:                    final String property = propertyChangeEvent.getProperty();
  80:                    fireHandlerChanged(new HandlerEvent(ActionHandler.this,
  81:                            IAction.ENABLED.equals(property), IAction.HANDLED
  82:                                    .equals(property)));
  83:                }
  84:            };
  85:        }
  86:
  87:        this.action.addPropertyChangeListener(propertyChangeListener);
  88:    }
  89:
  90:    /**
  91:     * When no more listeners are registered, then this is used to removed the
  92:     * property change listener from the underlying action.
  93:     */
  94:       private final void detachListener() {
  95:        this.action.removePropertyChangeListener(propertyChangeListener);
  96:        propertyChangeListener = null;
  97:    }
  98:
  99:    /**
100:     * Removes the property change listener from the action.
101:     *
102:     * @see org.eclipse.core.commands.IHandler#dispose()
103:     */
104:       public final void dispose() {
105:           if (hasListeners()) {
106:            action.removePropertyChangeListener(propertyChangeListener);
107:        }
108:    }
109:   
110:    public final Object execute(final ExecutionEvent event)
111:               throws ExecutionException {
112:        if ((action.getStyle() == IAction.AS_CHECK_BOX)
113:                   || (action.getStyle() == IAction.AS_RADIO_BUTTON)) {
114:            action.setChecked(!action.isChecked());
115:        }
116:        final Object trigger = event.getTrigger();
117:           try {
118:               if (trigger instanceof Event) {
119:                action.runWithEvent((Event) trigger);
120:            } else {
121:                action.runWithEvent(new Event());
122:            }
123:        } catch (Exception e) {
124:            throw new ExecutionException(
125:                    "While executing the action, an exception occurred", e); //$NON-NLS-1$
126:        }
127:        return null;
128:    }
129:
130:    /**
131:     * Returns the action associated with this handler
132:     *
133:     * @return the action associated with this handler (not null)
134:     * @since 3.1
135:     */
136:       public final IAction getAction() {
137:        return action;
138:    }
139:   
140:       public final boolean isEnabled() {
141:        return action.isEnabled();
142:    }
143:   
144:       public final boolean isHandled() {
145:        return action.isHandled();
146:    }
147:   
148:    public final void removeHandlerListener(
149:               final IHandlerListener handlerListener) {
150:        super.removeHandlerListener(handlerListener);
151:
152:           if (!hasListeners()) {
153:            detachListener();
154:        }
155:    }
156:   
157:       public final String toString() {
158:        final StringBuffer buffer = new StringBuffer();
159:
160:        buffer.append("ActionHandler("); //$NON-NLS-1$
161:        buffer.append(action);
162:        buffer.append(')');
163:
164:        return buffer.toString();
165:    }
166:}