Mobile Programming Pit Stop

Here’s a sample application that I created to use J2ME/JavaME Location API. The example should work with most modern phone which implements JSR-179. The application will display your current coordinates in Latitude, Longitude using GPS-enabled phone.

With simple modification, you can use LocationListener to estimate the speed of vehicle you’re travelling with this simple application.

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.location.*;

public class loctest extends MIDlet implements CommandListener
{
	private Display display;
	private Form form;
	private Command cmdExit,cmdOK;
	private StringItem si;

	public loctest()
	{

		display =Display.getDisplay(this);
		form = new Form("Location Api test");
		cmdExit = new Command("Exit",Command.EXIT,5);
		cmdOK = new Command("OK",Command.OK,1);
		si = new StringItem("Geo Location", "Click OK");
		form.append(si);
		form.addCommand(cmdOK);
		form.addCommand(cmdExit);
		form.setCommandListener(this);

	}

	public void startApp()
	{
		display.setCurrent(form);
	}

	public void pauseApp()
	{

	}

	public void destroyApp(boolean flag) {
		notifyDestroyed();
	}

	public void commandAction(Command c, Displayable d)
	{
		if (c == cmdOK){
			Retriever ret = new Retriever(this);
			ret.start();

		} else if (c == cmdExit) {
			destroyApp(false);
		}
	}

	public void displayString(String string)
	{
		si.setText(string);
	}
}

class Retriever extends Thread {

	private loctest midlet;

        public Retriever(loctest midlet)
		{
			/**
			  * Constructor
			  *
			  * EFFECTS: Initialise the server and store midlet information
			  *
			  * @param midlet The main application midlet
			  * @param server Forecast Server URL
			  *
			  */
			this.midlet = midlet;

	}

	public void run()
		{
			/**
			* Entry point of the thread
			*
			* EFFECTS: call to connect() method
			*/
			try {
							checkLocation();
						} catch (Exception ex)
						{
							ex.printStackTrace();
							midlet.displayString(ex.toString());
			}
		}

	public void checkLocation() throws Exception
	{
		String string;
		Location l;
		LocationProvider lp;
		Coordinates c;
		// Set criteria for selecting a location provider:
		// accurate to 500 meters horizontally
		Criteria cr= new Criteria();
		cr.setHorizontalAccuracy(500);

		// Get an instance of the provider
		lp= LocationProvider.getInstance(cr);

		// Request the location, setting a one-minute timeout
		l = lp.getLocation(60);
		c = l.getQualifiedCoordinates();

		if(c != null ) {
		  // Use coordinate information
		  double lat = c.getLatitude();
		  double lon = c.getLongitude();
		  string = "\nLatitude : " + lat + "\nLongitude : " + lon;

		} else {
			string ="Location API failed";
		}
		midlet.displayString(string);
	}
}

Please note that not all JSR-179 enabled phone supports this feature as some of those features depends on external factor such as the availability of GPS signal, type of your network and telco features.

Requirements
This application requires MIDP2.0/CLDC 1.1 with JSR 179 Location API enabled phone like Nokia N95

For more information, please refer to List of Mobile Phones that supports JSR-179 Location API

The sample application that I build here was compiled using Sun Java Wireless Toolkit 2.5.1

Download Sample Application
LocationTest.zip (8KB)

[tags]gps,java,j2me,javame,mobile,pda,jsr-179,midlet[/tags]

Random Posts

• Turn your Pocket PC PDA into iPhone with iContact
• Another Attack hits Mobilepit.com
• Compact MD5 class library for J2ME / JavaME app
• Pocket SharpMT – Free Pocket PC Blogging Client
• Create PC Bluetooth application easily with pybluez
• Generic AboutForm class for J2ME / JavaME application