Question

following code , it crashes when I uncomment the ‘list etc and add overlay when I add the overlay to list it crashes. I can add a single overlay icon in the ‘oncreate and it doesn’t crash, but adding it to the ‘onlocationchanged’ it crashes

 public class MainActivity extends MapActivity implements LocationListener {


MyLocationOverlay myLocationOverlay;

public MapView mapView;
MapController mc;

OverlayItem overlayitem;
List<Overlay> mapOverlays;
HelloItemizedOverlay itemizedoverlay;
GeoPoint myLocationGeoPoint;



private MockGpsProvider mMockGpsProviderTask = null;
//mMockGpsProviderTask = new MockGpsProvider();

/* This method is called when use position will get changed */
public void onLocationChanged(Location location) {
    GeoPoint myLocationGeoPoint = new GeoPoint((int)(location.getLatitude() * 1e6) , (int)(location.getLongitude() * 1e6));

//  Toast.makeText(this, "changinglocation", Toast.LENGTH_SHORT).show();
    String message = String.format(
            "New Location \n Longitude: %1$s \n Latitude: %2$s",
            (int)(location.getLongitude()), (int)(location.getLatitude())
    );
    Toast.makeText(this, message, Toast.LENGTH_LONG).show();
   // mc.setCenter(myLocationGeoPoint);
   mc.animateTo(myLocationGeoPoint);        
  // mc.setZoom(11);
    //}
 //     mapOverlays = mapView.getOverlays();
 // Drawable drawable = this.getResources().getDrawable(R.drawable.androidmarker);

  overlayitem = new OverlayItem(myLocationGeoPoint, "Hola, Mundo!", "I'm in Mexico City!");
   itemizedoverlay.addOverlay(overlayitem);
   mapOverlays.add(itemizedoverlay);

}



public void onProviderDisabled(String provider) {
    Toast.makeText(this, "No mock data mofo", Toast.LENGTH_SHORT).show();

}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
int test()
{
    int i1=getIntent().getIntExtra("key", -1);
    return(i1);
}

@Override
protected boolean isRouteDisplayed() {
    return false;
}
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    MapView mapView = (MapView) findViewById(R.id.mapview);
    mc = mapView.getController();
mapView.setBuiltInZoomControls(true);
mapView.setSatellite(true);
mc.setZoom(19);

 List<Overlay> mapOverlays = mapView.getOverlays();
 Drawable drawable = this.getResources().getDrawable(R.drawable.androidmarker);
 HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable, this);

 GeoPoint point = new GeoPoint(19240000,-99120000);
 //GeoPoint point = new GeoPoint(19240000,test());

 //GeoPoint point = new GeoPoint(19240000,message);
 OverlayItem overlayitem = new OverlayItem(point, "Hola, Mundo!", "I'm in Mexico City!");
 itemizedoverlay.addOverlay(overlayitem);
 mapOverlays.add(itemizedoverlay);

//   LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
//   Criteria criteria = new Criteria();
//  criteria.setAccuracy( Criteria.ACCURACY_COARSE );
//  String provider = lm.getBestProvider( criteria, true );

//  if ( provider == null ) {
//      Toast.makeText(this, "No mock data mofo", Toast.LENGTH_SHORT).show();

//  }

       /** Setup GPS. */
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    if(locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){ 
        /// use real GPS provider if enabled on the device
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
    }
    else if(!locationManager.isProviderEnabled(MockGpsProvider.GPS_MOCK_PROVIDER)) {
        // otherwise enable the mock GPS provider
        locationManager.addTestProvider(MockGpsProvider.GPS_MOCK_PROVIDER, false, false,
                false, false, true, false, false, 0, 5);
        locationManager.setTestProviderEnabled(MockGpsProvider.GPS_MOCK_PROVIDER, true);
        Toast.makeText(this, "mock data enabled mofo", Toast.LENGTH_SHORT).show();
    }  
    if(locationManager.isProviderEnabled(MockGpsProvider.GPS_MOCK_PROVIDER)) {
        locationManager.requestLocationUpdates(MockGpsProvider.GPS_MOCK_PROVIDER, 0, 0, this);

        /** Load mock GPS data from file and create mock GPS provider. */
        try {
            // create a list of Strings that can dynamically grow
            List<String> data = new ArrayList<String>();

            /** read a CSV file containing WGS84 coordinates from the 'assets' folder
             * (The website http://www.gpsies.com offers downloadable tracks. Select
             * a track and download it as a CSV file. Then add it to your assets folder.)
             */         
            InputStream is = getAssets().open("mock_gps_data.csv");
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));

            // add each line in the file to the list
            String line = null;
            while ((line = reader.readLine()) != null) {
                data.add(line);
            }

            // convert to a simple array so we can pass it to the AsyncTask
            String[] coordinates = new String[data.size()];
            data.toArray(coordinates);

            // create new AsyncTask and pass the list of GPS coordinates
            mMockGpsProviderTask = new MockGpsProvider();
            mMockGpsProviderTask.execute(coordinates);
        } 
        catch (Exception e) {}
    }




        }
private class MockGpsProvider extends AsyncTask<String, Integer, Void> {
    public static final String LOG_TAG = "GpsMockProvider";
    public static final String GPS_MOCK_PROVIDER = "GpsMockProvider";

    /** Keeps track of the currently processed coordinate. */
    public Integer index = 0;

    @Override
    protected Void doInBackground(String... data) {         
        // process data
        for (String str : data) {
            // skip data if needed (see the Activity's savedInstanceState functionality)
            if(index < 5) {
                index++;
                continue;
            }               

            // let UI Thread know which coordinate we are processing
            publishProgress(index);

            // retrieve data from the current line of text
            Double latitude = null;
            Double longitude = null;
            Double altitude= null;
            try {
                String[] parts = str.split(",");
                latitude = Double.valueOf(parts[0]);
                longitude = Double.valueOf(parts[1]);
                altitude = Double.valueOf(parts[2]);
            }
            catch(NullPointerException e) { break; }        // no data available
            catch(Exception e) { continue; }                // empty or invalid line

            // translate to actual GPS location
            Location location = new Location(GPS_MOCK_PROVIDER);
            location.setLatitude(latitude);
            location.setLongitude(longitude);
            location.setAltitude(altitude);
            location.setTime(System.currentTimeMillis());

            // show debug message in log
            Log.d(LOG_TAG, location.toString());

            // provide the new location
            LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
            locationManager.setTestProviderLocation(GPS_MOCK_PROVIDER, location);

            // sleep for a while before providing next location
            try {
                Thread.sleep(200);

                // gracefully handle Thread interruption (important!)
                if(Thread.currentThread().isInterrupted())
                    throw new InterruptedException("");
            } catch (InterruptedException e) {
                break;
            }

            // keep track of processed locations
            index++;
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        Log.d(LOG_TAG, "onProgressUpdate():"+values[0]);
        mMockGpsProviderIndex = values[0];
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

Answer 1

You would declare all the variables used inside onLocationChanged() as global variables to avoid reallocating of memory and errors, the reason it works in onCreate() method is that it executes one time only while onLocationChanged() executes several times whenever the location is changed.

EDIT:

You didn’t add any request for location updates in your onCreate() method. Please see this link to follow best strategies of getting location updates.