Codename one GPS tracker

Question

I want to track the device with GPS signal. At the same time show latitude, longitude, altitude and speed.

I use this code and there is no result on the screen:

@Override
protected void onGpsTracker_ButtonAction(Component c, ActionEvent event) {
    try {
        int i = 0;
        Location loc = mylocLocationManager.getCurrentLocation();
        if(loc.getStatus()==LocationManager.AVAILABLE) {
        } else {
            Dialog.show("Error!", "Falla de señal", "OK", null);
        }
        mylocLocationManager.setLocationListener(new LocationListener() {
            public void locationUpdated(Location location) {
                gpsLocation= location;
                Component c = null;
                Label labelalt = (Label)findByName("altitudT", c);
                Label labellat = (Label)findByName("latitudT", c);
                Label labellng = (Label)findByName("longitudT", c);
                Label labeldist = (Label)findByName("distanciaT", c);
                Label labelspeed = (Label)findByName("speedT", c);
                altmax= location.getAltitude();
                double lat = location.getLatitude();
                double lng = location.getLongitude();
                float speed =  location.getVelocity();

                double alt = location.getAltitude();
                velprompos = velprompos + 1;
                totspeed = (int) (totspeed + speed);
                velopro = totspeed / velprompos;
                totalt = altmax - alt;

                velmax=speed;
                Coord lastLocation = new Coord(lat, lng);
                mapComponent.zoomTo(lastLocation, 15);

                prevdistance = totdistance;
                prevLon = currentLon;
                prevLat = currentLat;
                String Salt = String.valueOf(alt);
                labelalt.setText(Salt);
                String Slat = String.valueOf(lat);
                labellat.setText(Slat);
                String Slng = String.valueOf(lng);
                labellng.setText(Slng);
                String Sspeed = String.valueOf(speed);
                labelspeed.setText(Sspeed);

                //aca hay q pner dibujo lineas  
            }

            public void providerStateChanged(int newState) {
                //positionMethod();
            }
        });
    } catch (Exception ex) {
        ex.printStackTrace();
        gpsLocation = null;
    }
}     

The idea is to get the location when the device is moving, and show this results on some labels. Any help?

Answer 1

You are implementing couple of things wrongly.

1. Add @override to overriden methods like locationUpdated and providerStateChanged .

2. Don't re-declare Component c as and set it to null

3. Get your labels by calling them directly with find method and pass c as a parameter

4. revalidate or repaint your form after each update.

5. As a general advice, keep your variable declaration consistence, declare Number of Mangoes as numOfMangoes and not numberofmangoes nor numofmangoes nor Numberofmangoes.

   @Override
   protected void onGpsTracker_ButtonAction(Component c, ActionEvent event) {
       try {
           int i = 0;
           Location loc = mylocLocationManager.getCurrentLocation();
           if (loc.getStatus() == LocationManager.AVAILABLE) {
               System.out.println("Location available");
           } else {
               Dialog.show("Error!", "Falla de señal", "OK", null);
           }
           final LocationManager mylocLocationManager = LocationManager.getLocationManager();
           mylocLocationManager.setLocationListener(new LocationListener() {
               @Override
               public void locationUpdated(Location location) {
                   gpsLocation = location;
                   Label labelspeed = ;
                   altmax = location.getAltitude();
                   double lat = location.getLatitude();
                   double lng = location.getLongitude();
                   float speed = location.getVelocity();
   
                   double alt = location.getAltitude();
                   velprompos = velprompos + 1;
                   totspeed = (int) (totspeed + speed);
                   velopro = totspeed / velprompos;
                   totalt = altmax - alt;
   
                   velmax = speed;
                   Coord lastLocation = new Coord(lat, lng);
                   mapComponent.zoomTo(lastLocation, 15);
   
                   prevdistance = totdistance;
                   prevLon = currentLon;
                   prevLat = currentLat;
                   String Salt = String.valueOf(alt);
                   findAltitudT(c).setText(Salt);
                   String Slat = String.valueOf(lat);
                   findLatitudT(c).setText(Slat);
                   String Slng = String.valueOf(lng);
                   findLongitudT(c).setText(Slng);
                   String Sspeed = String.valueOf(speed);
                   findSpeedT(c).setText(Sspeed);
   
                   c.getComponentForm().revalidate();
                   //aca hay q pner dibujo lineas  
               }
   
               @Override
               public void providerStateChanged(int newState) {
                   //positionMethod();
               }
           });
   
       } catch (Exception ex) {
           ex.printStackTrace();
           gpsLocation = null;
       }
   }