Android Location Object Always Null

Question

I'm simply trying to write a method that returns Latitude and Longitude. I have an activity with a button and two text fields. The java class I am using extends AppCompatActivity and implements LocationListener When the button is pressed the following method is pressed:

public void startGPS(View view)
{

        // Here is the code to handle permissions - you should not need to edit this.
        if ( Build.VERSION.SDK_INT >= 23 &&
                ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[] { android.Manifest.permission.ACCESS_FINE_LOCATION, android.Manifest.permission.ACCESS_COARSE_LOCATION }, TAKE_PHOTO_PERMISSION);
        }

        Location location = locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 5000, 0, this);
}

Later on I try to print out my location in my onLocationChanged method but it was causing the app to crash. I ran it through the debugger and found that the location was always null .

I tried to this solution but it didn't work. Other examples are calling the function in onResume but I really need this to be in startGPS method.

Also, is there a chance that the error is just with my device? I'm running it on a Nexus 7 which doesn't seem to have any problems when I run Google Maps.

Answer 1

Because Android doesn't track location when no app is requesting it, in order to save battery. GetLastKnownLocation will almost always return null. If you want an assured non-null response, use requestLocationUpdates or requestSingleLocation. Both of those are asynchronous though, so they will call a callback when a location is found (actually figuring out a location can take from a few seconds to a minute or two, depending on the type of location provider, atmospheric conditions, line of sight issues, etc. If using GPS and inside it could actually never occur.)

Answer 2

If are trying to return the GPS Coordinates after pressing a button that chances are you don't already have an existing GPS location stored. You should be using requestLocationUpdates and not getLastKnownLocation .

locationManager.requestLocationUpdate(LocationManager.NETWORK_PROVIDER, 5000, 0, locationListener)

When you use requestLocationUpdate it will automatically call onLocationChanged for you so you don't need to call it in your code.

You can substitute LocationManager.NETWORK_PROVIDER for LocationManager.GPS_PROVIDER but as long as you have a WiFi connection you should be able to get coordinates.

Answer 3

If you are trying to use this inside try switching GPS_PROVIDER to NETWORK_PROVIDER ; this will work anywhere that the phone has service.