DatabaseModelEventManager.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.motorolamobility.studio.android.db.core.event;

import java.util.ArrayList;
import java.util.List;

import com.motorolamobility.studio.android.db.core.ui.ITreeNode;

/**
 * Manager which notifies {@link IDatabaseModelListener} registered that a {@link DatabaseModelEvent} occurred. 
 * It is a singleton that needs to be called by the hierarchy of {@link ITreeNode} items when they modify the database model.
 */
public class DatabaseModelEventManager
{
    private static DatabaseModelEventManager _instance;

    private final List<IDatabaseModelListener> listeners = new ArrayList<IDatabaseModelListener>();

    private DatabaseModelEventManager()
    {
        //Singleton - avoid extensions and other means to construct an instance 
    }

    /**
     * @return single instance of {@link DatabaseModelEvent}
     */
    public synchronized static DatabaseModelEventManager getInstance()
    {
        if (_instance == null)
        {
            _instance = new DatabaseModelEventManager();
        }
        return _instance;
    }

    /**
     * Adds a new {@link IDatabaseModelListener} 
     * @param listener 
     */
    public void addListener(IDatabaseModelListener listener)
    {
        synchronized (listener)
        {
            listeners.add(listener);
        }
    }

    /**
     * Removes the {@link IDatabaseModelListener} 
     * @param listener
     */
    public void removeListeners(IDatabaseModelListener listener)
    {
        synchronized (listener)
        {
            listeners.remove(listener);
        }
    }

    /**
     * Fires/notifies/deliver the event to the listeners registered.  
     * @param node {@link ITreeNode} that needs to refresh the view based on the model
     * @param eventType
     */
    public void fireEvent(ITreeNode node, DatabaseModelEvent.EVENT_TYPE eventType)
    {
        DatabaseModelEvent databaseModelEvent = new DatabaseModelEvent(node, eventType);
        synchronized (listeners)
        {
            if (listeners != null)
            {
                for (IDatabaseModelListener listener : listeners)
                {
                    switch (eventType)
                    {
                        case ADD:
                            listener.handleNodeAdditionEvent(databaseModelEvent);
                            break;
                        case REMOVE:
                            listener.handleNodeRemovalEvent(databaseModelEvent);
                            break;
                        case UPDATE:
                            listener.handleNodeUpdateEvent(databaseModelEvent);
                            break;
                        case CLEAR:
                            listener.handleNodeClearEvent(databaseModelEvent);
                            break;
                        case EXPAND:
                            listener.handleNodeExpandEvent(databaseModelEvent);
                            break;
                        case SELECT:
                            listener.handleNodeSelectEvent(databaseModelEvent);
                            break;
                        default:
                            break;
                    }
                }
            }
        }
    }
}