Getting the number of satellites from Location object

I'm using a GPS provider and L开发者_StackOverflow社区ocationListener.onLocationChanged(Location location) to receive location fixes.

Documentation says, that Location.getExtras() contains next key/value pair:

satellites - the number of satellites used to derive the fix

but on practice I'm getting an empty extra object - there is no any data there.

Does it means that I'm getting the A-GPS fixes and not GPS?

To get the number of satellites used by the GPS engine you need to implement android.location.GpsStatus.Listener and implement its method onGpsStatusChanged().

Example...

public void onGpsStatusChanged(int event) {
    int satellites = 0;
    int satellitesInFix = 0;
    int timetofix = locationManager.getGpsStatus(null).getTimeToFirstFix();
    Log.i(TAG, "Time to first fix = " + timetofix);
    for (GpsSatellite sat : locationManager.getGpsStatus(null).getSatellites()) {
        if(sat.usedInFix()) {
            satellitesInFix++;              
        }
        satellites++;
    }
    Log.i(TAG, satellites + " Used In Last Fix ("+satellitesInFix+")"); 
}

I use Location.getExtras().getInt("satellites"), and it give the number of satellites in use.

Since Android API 24 GpsStatus is deprecated and one should use GnssStatus. Let us have an activity or a service processing Gps data and a LocationManager already created.

private GnssStatus.Callback gnssCallback;

public void initCallbacks() {
    ....
    gnssCallback = new GnssStatus.Callback() {
        @Override
        public void onSatelliteStatusChanged(@NonNull GnssStatus status) {
            final int satelliteCount = status.getSatelliteCount();
            int usedCount = 0;
            for (int i = 0; i < satelliteCount; ++i)
                if (status.usedInFix(i))
                    ++usedCount;
            Log.d("MyServiceTag", "satellites count = " + satelliteCount + ", used = " + usedCount);
        }
    };
    locationManager.registerGnssStatusCallback(gnssCallback, new Handler(Looper.myLooper()));
    ....
}

public void deinitCallbacks() {
    ....
    locationManager.unregisterGnssStatusCallback(gnssCallback);
    ....
}

initCallbacks() should be called after locationManager initialization. deinitCallbacks() should be called when information on the number of satellites is no longer needed, e.g. in onDestroy(). GnssStatus.getSatelliteCount() returns total number of known satellites, GnssStatus.usedInFix(int i) tells whether i-th satellite had been used in the most actual location capture.

Nope it means that your phone manufacturer decided not to implement this. (Or you could be using the NETWORK_PROVIDER which does not use satellites)

Use a NmeaListener and parse the sentences to know the number of satellites visible or used.