Action.java

/**
 * 
 * Funf: Open Sensing Framework
 * Copyright (C) 2010-2011 Nadav Aharony, Wei Pan, Alex Pentland.
 * Acknowledgments: Alan Gardner
 * Contact: nadav@media.mit.edu
 * 
 * Author(s): Pararth Shah (pararthshah717@gmail.com)
 * 
 * This file is part of Funf.
 * 
 * Funf is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 * 
 * Funf is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with Funf. If not, see <http://www.gnu.org/licenses/>.
 * 
 */
package edu.mit.media.funf.action;

import java.lang.Runnable;

import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;

public class Action implements Runnable {
    
    private Looper looper = null;
    private Handler handler = null;
    
    Action() {
    }
        
    protected Handler getHandler() {
        return handler;
    }
    
    public void setHandler(Handler handler) {
        if (this.handler != null) {
            exitHandler();
        }
        this.handler = handler;
    }
    
    @Override
    public final void run() {
        if (isLongRunningAction()) {
            ensureHandlerExists();
            if (Looper.myLooper() != getHandler().getLooper()) {
                getHandler().post(this);
                return;
            }
        }
        execute();
    }
    
    /**
     * Override this function to include the action-specific code.
     */
    protected void execute() {
        // Perform action here
    }
    
    protected boolean isLongRunningAction() {
        return false;
    }
    
    protected void ensureHandlerExists() {
        if (handler == null) {
            synchronized (this) {
                if (looper == null) {
                    HandlerThread thread = new HandlerThread("Action[" + getClass().getName() + "]");
                    thread.start();
                    looper = thread.getLooper();
                    handler = new Handler(looper);
                }
            }
        }
    }
    
    protected void exitHandler() {
        if (handler != null) {
            synchronized (this) {
                if (looper != null) {
                    looper.quit();
                    looper = null;
                    handler = null;                    
                }
            }
        }   
    }
    
}