Onlocationchanged Callback Is Never Called

OnLocationChanged callback is never called

It looks like you setup should work, since it doesn't, I would make your example as simple as possible in order to troubleshoot. I would make your request look like

requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

This way you get ALL the updates possible. And comment out the part about getting the last known location. It's not needed yet.

Then in onLocationChanged(), just have

Log.v(TAG, "IN ON LOCATION CHANGE, lat=" + latitude + ", lon=" + longitude);

Comment out the rest so that you keep your listener active. This should give you a stream of updates on a real device. On the emulator, you'll need to use DDMS, and you'll get one GPS update each time you press send.

onLocationChanged() never called

Do you never get a location or only as you write in your comment "sometimes it gets location but not at the time of click."?

Might be that your code is faster than LocationManager, which might not yet have called onLocationChanged(). Change your code in order to get the last known location, or wait until your locListener was called:

locManager.requestLocationUpdates(
  LocationManager.GPS_PROVIDER, 1000, 1, locListener);
mobileLocation = locManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (mobileLocation != null) {

onLocationChanged is not called automatically

Problem seems to be solved.
In onCreate, I added:

Criteria crit = new Criteria();
crit.setAccuracy(Criteria.ACCURACY_FINE);
best = mgr.getBestProvider(crit, false);
mgr.requestLocationUpdates(best, 0, 1, locationListener);

onLocationChanged now looks like that:

@Override
public void onLocationChanged(Location location) {
    i++;
    nextPoint = overlay.getMyLocation();
    latitude = nextPoint.getLatitudeE6();
    longtitude = nextPoint.getLongitudeE6();
    lastPoint = new GeoPoint((int) latitude, (int) longtitude);
    Points.add(lastPoint);
    MapOverlay mapOverlay = new MapOverlay(Points.get(i - 1), Points.get(i));
    map.getOverlays().add(mapOverlay);
    mMapController.animateTo(Points.get(i));
    nextPoint = null;
    lastPoint = null;
}

Also, very important methods:

@Override
protected void onResume() {
    super.onResume();
    mgr.requestLocationUpdates(best, 10000, 1, locationListener);
}

@Override
protected void onPause() {
    super.onPause();
    mgr.removeUpdates(locationListener);
}

And also some new permissions:

<uses-permission android:name="android.permission.ACCESS_GPS" />
        <uses-permission android:name="android.permission.ACCESS_LOCATION" />
        <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
        <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
        <uses-permission android:name="android.permission.INTERNET" />

onLocationChanged() callback is never called until I turn on my device location tracker manually

If you want to track location on android you have to turn on tracker in settings. As far as I know there is no way to do it automatically.

So answering your question directly, there is no way to do it. Standard solution is to ask user to turn tracking on and open settings menu.

For example:

/**
 * Function to show settings alert dialog
 * */
public void showSettingsAlert(){
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

    // Setting Dialog Title
    alertDialog.setTitle("GPS is settings");

    // Setting Dialog Message
    alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

    // Setting Icon to Dialog
    //alertDialog.setIcon(R.drawable.delete);

    // On pressing Settings button
    alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,int which) {
            Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            mContext.startActivity(intent);
        }
    });

    // on pressing cancel button
    alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
        dialog.cancel();
        }
    });

    // Showing Alert Message
    alertDialog.show();
}

This is the link to the tutorial:
http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial/

Callback method onLocationChanged() is not working on viewmodel

In you view model

public class MAgencyViewModel extends AndroidViewModel {
    
    private LocationCallback locationCallback;
    public boolean requestingLocationUpdates;

    public MAgencyViewModel(Application app) {
        super(app);
        locationCallback = new LocationCallback() {
            @Override
            public void onLocationResult(LocationResult locationResult) {
                if (locationResult == null) {
                return;
                }
                for (Location location : locationResult.getLocations()) {
                    // Update UI with location data
                    // ...
                }
            }
        };
    }

    public void startLocationUpdates() {
        requestingLocationUpdates = true
        LocationServices.getFusedLocationProviderClient(getApplication())
           .requestLocationUpdates(locationRequest,
               locationCallback,
               Looper.getMainLooper());
    }

    public void stopLocationUpdates() {
        requestingLocationUpdates = false
        LocationServices.getFusedLocationProviderClient(getApplication())
        .removeLocationUpdates(locationCallback);
    }
}

Now in your Fragment/Activity override on pause and onresume

Then call the startlocation and stoplction in your viewmodel

@Override
protected void onPause() {
    super.onPause();
    viewModel.stopLocationUpdates();
}
@Override
protected void onResume() {
    super.onResume();
    if (viewModel.requestingLocationUpdates) {
    startLocationUpdates();
}

Notice setting and checking boolean requestingLocationUpdates if locationRequest is active

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