Callback method onLocationChanged() is not working on viewmodel

Question

I'm trying to get location information in ViewModel.

So I called requestLocationUpdates() by getting LocationManager at View.

I'm not sure requestLocationUpdates() works in viewmodel because callback method onLocationChanged() is not working.

I'm new on android so I don't know what's wrong in here. Because there was no error on this code.

I guess the error is occuring because callback method onLocationChanged() is not getting called at ViewModel.

How can make this work??

This is my code.

ViewModel Class

public class MAgencyViewModel extends ViewModel implements LocationListener {

    private final String TAG = "MAgencyViewModel";

    //이 클래스에서는 Model과 통신하여서 날씨 정보를 받아온다.
    private MutableLiveData<ShortWeather> sw;
    private MAgencyRepo maRepo;
    private GeoInfo gi;
    private GpsTransfer gpt;

//    public void init(GeoInfo gi) {
//        if (sw != null) {
//            return;
//        }
//
//        maRepo = MAgencyRepo.getInStance();
//        sw = maRepo.getWeather(gi); // this part is calling a weather api
//        Log.i(TAG, "API Connection finish");
//    }

    public LiveData<ShortWeather> getWeather() {
        return sw;
    }

    @SuppressLint("MissingPermission")
    //이부분은 권한 재확인 안하게 해주는 부분이다. 따로 재확인을 안하는 이유는 Activity단에서 이미 확인을 거쳤기 때문이다.
    public void locationUpdate(LocationManager lm) {
        Log.i(TAG, "locationUpdate()");
//        lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,this); //위치정보를 update하는 함수 이건 실제 기기용

        lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this); //After this nothing is happening
    }

    //여기서는 이제 위치 정보가 변경 되었을때 진입하는 부분
    @Override
    public void onLocationChanged(Location location) { //This CallBack method is not working
        Log.i(TAG, "onLocationChanged()");
    }

    //위치 정보 이용 권한 허가를 받지 못했을떄 호출 하는 부분
    public void defaultLocation() {


        //GpsTransfer 객체 생성
        gpt = new GpsTransfer();

        //GpsTransfer 위도와 경도를 원주로 설정
        gpt.setxLat(76);
        gpt.setyLon(122);
        gpt.transfer(gpt, 1);

        gi = new GeoInfo();

        gi.setLon(gpt.getyLon());
        gi.setLat(gpt.getxLat());

        getTime();

        if (sw != null) {
            return;
        }

        //해당 정보를 API를 호출
        maRepo = MAgencyRepo.getInStance();
        sw = maRepo.getWeather(gi); // this part is calling a weather api
        Log.i(TAG, "API Connection finish");
    }

    public void getTime() {

        SimpleDateFormat dateSdf = new SimpleDateFormat("yyyyMMdd"); //년월일 받아오는 부분
        SimpleDateFormat timeSdf = new SimpleDateFormat("HH"); //현재시간 받아오는 부분

        Calendar cal = Calendar.getInstance(); //현재시간을 받아온다.

        gi.setNowDate(dateSdf.format(cal.getTime())); //날짜 세팅
        gi.setNowTime(timeSdf.format(cal.getTime())); //시간 세팅

        /*
         * 하루 전체의 기상예보를 받아오려면 전날 23시에 266개의 날씨정보를 호출해와야 한다.
         * 따라서 호출 값은 현재 날짜보다 1일전으로 세팅해줘야 한다.
         * */

        cal.add(Calendar.DATE, -1); //1일전 날짜를 구하기 위해 현재 날짜에서 -1 시켜주는 부분
        gi.setCallDate(dateSdf.format(cal.getTime())); //1일전 값으로 호출값 생성


        Log.i(TAG, "DATE : " + gi.getNowDate());
        Log.i(TAG, "TIME : " + gi.getNowTime());
        Log.i(TAG, "CALL DATE : " + gi.getCallDate());

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}

Answer 1

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