Why does my OnLocationChanged() never get called?

Question

What I am trying to do:

I am trying to develop an app that only requires the user's location at the start of one activity. So only when the user is within the activity, the location gets updated either by network or GPS. Accordingly, the user may choose an indoor map.

What is my problem:

However, I find that the app is always using the history location, and never updates the location. I suspect there must be something wrong with my

location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER)

But I am not sure where the problem is.

Related code snippet:

In my Activity, I have:

    locationDetector = new LocationDetector(MapSelectionActivity.this);
    // try to get the current location
    if (locationDetector.checkLocationServiceAvailability()) {
        location = locationDetector.getLocation();
        if (location != null) {
            latitude = location.getLatitude();
            longitude = location.getLongitude();
        }
        Log.d("MapSelectionActivity", latitude + " " + longitude);
        //locationDetector.stopLocalization(); // stop the localization to save the energy
    } else { // if no location service, requires the user to turn GPS on
        locationDetector.showSettingsAlert();
    }

My LocationDetector class is as follows:

public final class LocationDetector implements LocationListener {

    private final Context mContext;

    private boolean isNetworkEnabled = false;
    private boolean isGPSEnabled = false;
    private boolean canGetLocation = false;

    private Location location;
    private String providerUsed;

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; // 0 meters
    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = (long) (1000 * 60 * 0.5); // 0.5 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    // constructor
    public LocationDetector(Context context) {

        this.mContext = context;

        locationManager = (LocationManager) mContext.getSystemService(Context.LOCATION_SERVICE);
    }

    // NOTE call  checkLocationServiceAvailability(); first before calling this!
    public Location getLocation() {
// I SUSPECT SOMETHING IS WRONG HERE
        if (isNetworkEnabled) { // use network

            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
            Log.d("LocationDetector", "Using Network");
            if (locationManager != null) {
                location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            }

            providerUsed = "Network";

        } else if (isGPSEnabled) { // use GPS

            if (location == null) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("LocationDetector", "Using GPS");
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                }
            }

            providerUsed = "GPS";

        } else { // neither the network nor the GPS is on

            providerUsed = null;

            Toast.makeText(mContext, "Location service is unavaliable", Toast.LENGTH_SHORT).show();
        }

        return location;
    }

    // call this to restart requesting the detecting
    public void startLocalization() {

        if (locationManager != null) {
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
        }
    }

    // call this to stop the detecting to save power
    public void stopLocalization() {

        if (locationManager != null) {
            locationManager.removeUpdates(LocationDetector.this);
        }
    }

    // check location service availability
    public boolean checkLocationServiceAvailability() {

        // check GPS on or off
        isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        // check Internet access
        ConnectivityManager connectivityManager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = connectivityManager.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnected()) {
            isNetworkEnabled = true;
        } else {
            isNetworkEnabled = false;
        }

        if (isGPSEnabled || isNetworkEnabled) {
            canGetLocation = true;
        } else {
            canGetLocation = false;
        }

        return canGetLocation;
    }

    public String getLocationProvider() {

        return providerUsed;
    }

    // show alert dialog to direct the users to the settings
    public void showSettingsAlert() {

        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // make it uncancellable
        alertDialog.setCancelable(false);

        // Setting Dialog Title
        alertDialog.setTitle("Forgot to turn GPS on?");

        // Setting Dialog Message
        alertDialog.setMessage("Currently there is no Internet access.\n\nLocalization requires GPS when Internet is unavailiable.\n\nDo you want to enable GPS so as to proceed?");

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

                Toast.makeText(mContext, "After enabling GPS, press the physical 'Back' button to return", Toast.LENGTH_LONG).show();
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();

                Toast.makeText(mContext, "No location service, please choose map manually", Toast.LENGTH_LONG).show();
            }
        });

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

    @Override
    public void onLocationChanged(Location _location) {
// IT NEVER GETS CALLED
        location = _location;

        // update the text view
        MapSelectionActivity.coordinatesTextView.setText("(" + Math.round(location.getLatitude() * 1000) / 1000.0 + ", " + Math.round(location.getLongitude() * 1000) / 1000.0 + ")");

        // update the marker on Google Maps
        MapSelectionActivity.googleMap.clear();
        MapSelectionActivity.googleMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude(), location.getLongitude())).title("I am here!"));
        MapSelectionActivity.googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(location.getLatitude(), location.getLongitude()), 15)); // 15 is the approporiate zooming level

        // re-suggest the map
        int recommendedMapSequenceNumber = MapSelectionActivity.mapDatabase.getMapSequenceNumber(location.getLatitude(), location.getLongitude());
        MapSelectionActivity.recommendedMapTextView.setTextColor(Color.parseColor("red"));
        if (recommendedMapSequenceNumber == -1) { // the so-called nearest is still too far

            Toast.makeText(mContext, "Please manually select one to proceed", Toast.LENGTH_LONG).show();
            MapSelectionActivity.recommendedMapTextView.setText("No recommended maps");
            MapSelectionActivity.autoSelectButton.setEnabled(false);
        } else { // suggest a map

            Toast.makeText(mContext, "One suitable map found", Toast.LENGTH_SHORT).show();
            MapSelectionActivity.recommendedMapTextView.setText(MapSelectionActivity.mapDatabase.getMapName(recommendedMapSequenceNumber));
        }

        Toast.makeText(mContext, "New location detected", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

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

    }

}

I never see the Toast in onLocationChanged(), which means that it never gets called! Also from the map, I can see the position is not updated.

Solution

Since this seems to be a common issue with getting Android Locations, I'll put down a quick checklist of common fixes:

---

1. Check your manifest!

   One of the most common issues is that the right permissions were never given. If you are using GPS (with or without Network), use <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>, else use <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>. Google's FusedLocationApi requires ACCESS_FINE_LOCATION.

---

2. (For Android 6+) Check runtime permissions!

   Check for and request permissions! If you are never given permissions, you'll end up with crashes, or worse (if you are catching all exceptions), you'll end up with no indication of anything! It doesn't matter if the user grants you permission at the start of the app, always check to see if you have permissions for all calls. The user can easily go to their settings and revoke them.

---

3. Double check your code!

   Are you sure you are passing in the right listener? Did you add that BroadcastReceiver or IntentService to your manifest? Are you using PendingIntent.getService() on a BroadcastReceiver class, or getBroadcast() on an IntentService class? Are you sure you are not unregistering your listener somewhere else in your code immediately after requesting?

---

4. Check device settings!

   Obviously, make sure you have location services turned on.

   

   If you are using Network services, did you turn on "Scanning Always Available"? Do you have your location mode set to "Best" ("High Accuracy") or "Battery Saving" ("Network Only")?

   

   If you are using GPS, did you turn on "Best" ("High Accuracy") or "Device only" in location mode?

   

---

5. Double check your code!

   Yes, this is on here twice. Did you try using a LocationListener instead of a PendingIntent, or vice-versa, to ensure you actually implemented LocationManager properly? Are you sure that the location request isn't being removed in some part of the Activity or Service lifecycle that you didn't expect to happen?

---

6. Check your surroundings!

   Are you testing GPS on the first floor of a building in the middle of San Francisco? Are you testing Network locations in the middle of nowhere? Do you work in a secret underground bunker void of all radio signals, wondering why your device isn't getting location? Always double check your surroundings when trying to troubleshoot location problems!

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There could be many other less obvious reasons why location isn't working, but before searching out those esoteric fixes, just run through this quick checklist.