Student Student - 3 months ago 43
Android Question

getlastknownlocation always return null after I re-install the apk file via eclipse

Recently, I created a simple application to get the gps location and display on android phone.
At beginning I able to get the location after few try, but after i re-install the apk file, the getLastKnownLocation() always return a null value.

Development environment used:
- API 10 gingerbread 2.3.6
- GPS provider is used

below is the code i applied in my android project:

public class MyActivity extends MapActivity{
protected void onCreate(Bundle savedInstanceState) {


mapView = (MapView)findViewById(R.id.myTripMap);
mapController = mapView.getController();
mapView.setSatellite(false);
mapView.setStreetView(true);
mapView.displayZoomControls(false);
mapView.setBuiltInZoomControls(true);//
mapView.setClickable(true);
mapController.setZoom(14);


Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setAltitudeRequired(false);
criteria.setBearingRequired(false);
criteria.setCostAllowed(true);
criteria.setPowerRequirement(Criteria.POWER_LOW);
provider = locationManager.getBestProvider(criteria, true);
location = locationManager.getLastKnownLocation(provider);

updateMyCurrentLoc(location);

locationManager.requestLocationUpdates(provider, 2, 1,locationListener);



}


private final LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
updateMyCurrentLoc(location);
}

public void onProviderDisabled(String provider){
updateMyCurrentLoc(null);
}

public void onProviderEnabled(String provider){ }
public void onStatusChanged(String provider, int status,
Bundle extras){ }
};


private void updateMyCurrentLoc(Location location) {



if (location != null) {

// other codes to get the address and display
Toast.makeText(getBaseContext(), "provider used : "+provider).show(); //testing purpose
}
else {
str = "No location found";
Toast.makeText(getBaseContext(), str, Toast.LENGTH_SHORT).show();
}

}
}


Can anyone suggest a possible solution to solve the null value returned by getLastKnownLocation()?
Any helps will be appreciated. Thanks.

Answer

the getLastKnownLocation() this returns the last known location...after you re-install the app it will not have any last known location...so it will result in NPE...instead use below code

public Location getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            this.canGetLocation = true;
            if (isNetworkEnabled) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("Network", "Network Enabled");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("GPS", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

    return location;
}

It worked for me...should work for you too...

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