Issue with a ServerManager class

I have an app client-server thing...which is nothing else but a real tracking device. I mean the client is on an android phone and it sends to the server the GPS data....reaching data to the server I wanna send it to another activity....

The data is received in a worker thread and it send to a main activity.

For that I've used a ServerManager class in which the worker thread stores the last GPS data received.

this is the worker thread:

Scanner is = new Scanner(new DataInputStream(
                this.clientSocket.getInputStream()));

        while (!stop) {
            while (is.hasNext()) {
                try {
                    longitude = is.next();
                                            latitude = is.next();
                                          // save last data
                    ServerManager.getInstance().setLastLatitude(latitude);
                    ServerManager.getInstance().setLastLongitude(longitude);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

This is my ServerManager class:

public class ServerManager {

String lastLatitude;
String lastLongitude;

// singleton
private static ServerManager instance = null;

private ServerManager() {

}

public static ServerManager getInstance() {
    if (instance == null)
        instance = new ServerManager();
    return instance;
}

public String getLastLatitude() {
    return lastLatitude;
}

public void setLastLatitude(String lastLatitude) {
    this.lastLatitude = lastLatitude;
}

public String getLastLongitude() {
    return lastLongitude;
}

public void setLastLongitude(String lastLongitude) {
    this.lastLongitude = lastLongitude;
}

}

And finally this is the activity that asks for those points from the ServerManager class:

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.server4);    

    mapView = (MapView) findViewById(R.id.mapview1);
    mapView.setBuiltInZoomControls(true);
    mc = mapView.getController();


   longitude=Integer.parseInt(ServerManager.getInstance().getLastLongitude());
   latitude=Integer.parseInt(ServerManager.getInstance().getLastLatitude());

  p=new GeoPoint(longitude,latitude);

   theRouteDraw(p);//here I draw those points on the map

   }

Question:

Why when I try to call this last activity I get this eror:

05-08 23:45:40.409: ERROR/AndroidRuntime(360): Uncaught handler: thread main exiting due to uncaught exception

05-08 23:45:40.459: ERROR/AndroidRuntime(360): java.lang.RuntimeException: Unable t开发者_Go百科o start activity ComponentInfo{com.server/com.server.Server4}: java.lang.NumberFormatException: unable to parse 'null' as integer

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.os.Handler.dispatchMessage(Handler.java:99)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.os.Looper.loop(Looper.java:123)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at 

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at java.lang.reflect.Method.invokeNative(Native Method)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at java.lang.reflect.Method.invoke(Method.java:521)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at dalvik.system.NativeStart.main(Native Method)
05-08 23:45:40.459: ERROR/AndroidRuntime(360): Caused by: java.lang.NumberFormatException: unable to parse 'null' as integer

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at java.lang.Integer.parseInt(Integer.java:347)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at java.lang.Integer.parseInt(Integer.java:323)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at com.server.Server4.onCreate(Server4.java:47)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)

05-08 23:45:40.459: ERROR/AndroidRuntime(360):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)

UPDATE:

My app is kind of a GPS tracker.It has a part that does real time tracking.What does that mean???..............It means that the client it moves...over a route and all this GPS data that describes his movement along a route is sent to a server.

Each time the location is changed the new data is sent to the server part.

The server receives those points in a worker thread.....and after that I pass them to a ServerManager class.

Now,when I call for that activity(the last code in my initial question) I want it to ask from ServerManager the last data he has.....And I want it to ask for it as long as the client moves....

U said that I should use a handler to sent the data from woker to activity....But I want otherwise....-the activity to as for the data as long as the worker receives new updates.

Do u understand now????

UPDATE2:

protected GeoPoint doInBackground(Void...voids){


        try{

   longitude=Integer.parseInt(ServerManager.getInstance().getLastLongitude());
   latitude=Integer.parseInt(ServerManager.getInstance().getLastLatitude());

   p=new GeoPoint(longitude,latitude);
   publishProgress(p);

        }

        catch(Exception e)

        {
            e.printStackTrace();
        }
        return p;
    }

This is my doInBackground method....I have no errors,but I wonder what loop should I use inside of it in order for it to ask for data as long as I'm in that activity...and stop asking for data as soon as I leave the activity????

So....What loop to use?

Finally,this is what came up thanks@MByD

public class Server4 extends MapActivity {

    private LocationManager lm;

    private LocationListener locationListener;

    private MyLocationOverlay myLocOverlay;


    private MapView mapView;

    private MapController mc;

    GeoPoint p;

    InitTask init_task;

    int latitude;
    int longitude;
    DBAdapter db;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.server4);

        mapView = (MapView) findViewById(R.id.mapview1);
        mapView.setBuiltInZoomControls(true);
        mc = mapView.getController();
    }

    public void onResume() {

         super.onResume();
         init_task = new InitTask();
        init_task.execute();
    }

    public class InitTask extends AsyncTask<Void, GeoPoint, Void> {

        GeoPoint p;

        protected Void doInBackground(Void... voids) {

            try {

                while (true) {
                    longitude = Integer.parseInt(ServerManager.getInstance()
                            .getLastLongitude());
                    latitude = Integer.parseInt(ServerManager.getInstance()
                            .getLastLatitude());

                    p = new GeoPoint(longitude, latitude);
                    publishProgress(p);
                    Thread.sleep(500);
                }

            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        protected void onProgressUpdate(GeoPoint... progress1) {

            theRouteDraw(progress1[0]);
            //initMyLocation();

        }

    }

    public void onPause(){

        init_task.cancel(true);
        super.onPause();

    }

    public void theRouteDraw(GeoPoint p1) {
        mc.animateTo(p1);
        mc.setZoom(13);
        mapView.invalidate();
        mapView.setSatellite(true);

    }

    /*private void initMyLocation() {
        myLocOverlay = new MyLocationOverlay(this, mapView);
        myLocOverlay.enableMyLocation();
        mapView.getOverlays().add(myLocOverlay);

    }*/

    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

}

You are trying to parse null here: longitude=Integer.parseInt(ServerManager.getInstance().getLastLongitude());

Because you receive null from getLastLongitude()

Seems like worker thread didn't call setLastLatitude yet...

Edit:

1. Use loop inside doInBackground() and add sleep(X) at the end of the loop where X is the interval between checks.

2. Call cancel on the thread at onPause() method (and move the creation to onResume() as well).

Example:

   try{
       while(keepGoing) // some boolean that is set to true
       {
           longitude=Integer.parseInt(ServerManager.getInstance().getLastLongitude());
           latitude=Integer.parseInt(ServerManager.getInstance().getLastLatitude());

           p=new GeoPoint(longitude,latitude);
           publishProgress(p);
           Thread.sleep(interval); // interval specifies the time to wait in ms.
       }
   }
   ...