tracker.java

package com.syntheticdreams.tracker;

/* This project makes use of many standard javax libraries, especially in reading the GPS.
** The microedition package in javax contains a number of mobile device related libraries, including the
** location package, which has methods specially designed for working with coordinates and 
** pulling them from a GPS.  The Blackberry supports the use of this package interfacing with its GPS (for 
** providers that have not locked the phone.  Verizon has, until recently, locked the GPS of many of its models
** from use by third party applications.)  The rest of our package importing is mainly for the user interface. */
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.system.*;
import javax.microedition.location.*;
import javax.microedition.location.Location.*;
import javax.microedition.location.Criteria.*;
import javax.microedition.io.*;
import java.util.*;

// The UiApplication is a class designed for presenting a user interface to the user and maintaining screens on a stack.  
// See Creating a Blackberry Game - Part 2 for more info (http://www.toniwestbrook.com/archives/71)
public class tracker extends UiApplication 
{
    // Our main method is always called first, starts the ball rolling
    public static void main(String[] args)
    {
        // Create a new instance of the main "tracker" class, pushes the main screen onto the stack
        tracker trackerApp = new tracker();

        // Enter the event dispatcher to intercept key and trackball events
        trackerApp.enterEventDispatcher();
    }

    public tracker() 
    {    
        // See startScreen class below, our main screen where the magic takes place.  Push it onto the stack so
        // the user sees it and the instance of the class starts running and processing.
        pushScreen(new startScreen());
    }
} 

// Our only screen to be pushed on the screen stack
final class startScreen extends MainScreen
{
    // A timer that will continually poll the GPS
    Timer updateTimer = new Timer(); 
        
    // The specific task for our timer where the dirty work takes place
    TimerTask updateTask = new TimerTask()
    {       
        // The run method is what is actually run by the timer every time it resets
        public void run()
        {
            LocationProvider lp; // LocationProvider does the actual work of reading coordinates from the GPS
            Location currentLoc; // Stores component information of our position
            Criteria cr = new Criteria(); // Settings for the GPS - we can read it at different accuracy levels
            HttpConnection httpConn;  // An HTTP socket connection class to send our results to a webserver
            String getStr; 

            // I basically set no requirements on any of the horizontal, vertical, or power consumption requirements below.  
            // The distance components are set in meters if you do want to establish accuracy - the less the accuracy, the 
            // quicker and more likely a successful read (I believe). 
            // You can also set power consumption, between low, medium, high (or no requirement)
            // There are also a number of other settings you can tweak such as minimum response time, if altitude is required,
            // speed required, etc.  It all depends on the exact application you're writing and how specific you need the info to
            // be.  For our purposes, a rough coordinate is good enough.
            cr.setCostAllowed(true);
            cr.setHorizontalAccuracy(javax.microedition.location.Criteria.NO_REQUIREMENT);
            cr.setVerticalAccuracy(javax.microedition.location.Criteria.NO_REQUIREMENT);
            cr.setPreferredPowerConsumption(javax.microedition.location.Criteria.NO_REQUIREMENT);

            try
            {
                // Get a new instance of the location provider using the criteria we established above.
                lp = LocationProvider.getInstance(cr);
 
                // Now populate our location object with our current location (with a 60 second timeout)
                currentLoc = lp.getLocation(60);
            }

            // If we hit the timeout or encountered some other error, report it.
            catch(LocationException e)
            {
                Dialog.alert("Error getting coordinates");
                return;
            }

            // If reading the GPS was interrupted, report it
            catch(InterruptedException e)
            {
                Dialog.alert("GPS Interrupted!");
                return;    
            }

            // If we made it here, we got a successful read.  I transmit it to a webserver via a simple querystring.
            try
            {
                // I build the querystring here             
                // set the "lat" querystring var with the latitude from getLatitude
                getStr = "lat=" + currentLoc.getQualifiedCoordinates().getLatitude();

                //lon with longitude
                getStr = getStr + "&lon=" + currentLoc.getQualifiedCoordinates().getLongitude();

                // alt with altitude
                getStr = getStr + "&alt=" + currentLoc.getQualifiedCoordinates().getAltitude();

                // vel with speed
                getStr = getStr + "&vel=" + currentLoc.getSpeed();

                // Now I establish an http connection the webserver running a server side script that can read the values from
                // the querystring and save them to a database.  In my case, I had a simple ASP page that wrote them to a MSSQL
                // database - this database being read by another webpage that printed said coordinates out on a google map.  
                // But you could do the same with PHP, PERL, or any other server side language of your choice.
                httpConn = (javax.microedition.io.HttpConnection) javax.microedition.io.Connector.open("http://www.yourwebsitehere.com/yourpage.asp?" + getStr);

                // Just an easy GET with a querystring.
                httpConn.setRequestMethod(HttpConnection.GET);

                // Set HTTP values
                httpConn.setRequestProperty("Connection","close");
                httpConn.setRequestProperty("Content-Length","0");

                // Make the request (e.g. send the data)
                httpConn.getResponseCode();

                // Close the socket
                httpConn.close();
            }

            // If there was an error contacting the webserver, post it
            catch (java.io.IOException e)
            {
                Dialog.alert("Error contacting web server");
                return;
            }
        }
    };

    // Our main screen's constructor
    public startScreen()
    {
        super();

        // Set the window's title
        LabelField title = new LabelField("GPS Tracker", LabelField.ELLIPSIS | LabelField.USE_ALL_WIDTH);
        setTitle(title);

        // Feel free to snazz up your program with your own messages or real time info from the GPS
        add(new RichTextField("Starting transmission..."));

        // Add the update task to the update timer, running it starting in 10 milliseconds, and then every
        // 240000 milliseconds (4 minutes)
        updateTimer.scheduleAtFixedRate(updateTask, 10, 240000);                   
    }
    
    // Cleanup on close
    public boolean onClose()
    {
       Dialog.alert("Transmission Ended!");
       System.exit(0);
       return true;    
    }
}