gnss的状态未更新

Question

我有这段代码来获取一些GNSS状态更新。我基本上是在检查代码是否要转到方法onSatelliteStatusChanged

import android.Manifest;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.location.GnssMeasurement;
import android.location.GnssMeasurementsEvent;
import android.location.GnssStatus;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.UserHandle;
import android.text.method.ScrollingMovementMethod;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collection;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;

import static android.content.Context.LOCATION_SERVICE;

public class GNSSTestFragment extends Fragment implements LocationListener {

    private final String TAG = "GNSS TEST";
    private static final int REQUEST_LOCATION = 111;
    private Context mContext;
    private LocationManager mLocationManager;
    private GnssStatus.Callback mGnssStatusCallback;
    private TextView measurementTextView;
    private final GnssMeasurementsEvent.Callback gnssMeasurementsEventListener =
        new GnssMeasurementsEvent.Callback() {
            @Override
            public void onGnssMeasurementsReceived(GnssMeasurementsEvent event) {
                Collection<GnssMeasurement> a = event.getMeasurements();
                for(final GnssMeasurement gnssMeasurement: a){
                    if(gnssMeasurement.getConstellationType() == GnssStatus.CONSTELLATION_GPS) {
                        ((Activity)mContext).runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                measurementTextView.setText("Cn0 = " + gnssMeasurement.getCn0DbHz());
                            }
                        });
                    }
                }
            }

            @Override
            public void onStatusChanged(int status) {
            }
        };
    private TextView numberSatellitesTextView;
    private Handler mHandler = new Handler();
    private boolean isLoadingProgress = false;
    private static int gnssError = ErrorTest.TEST_NOT_WORKING;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.gnss_test_fragment, container, false);
        mContext = getContext();
        numberSatellitesTextView = view.findViewById(R.id.number_satellites);
        measurementTextView = view.findViewById(R.id.gnss_measurement);
        measurementTextView.setMovementMethod(new ScrollingMovementMethod());
        mLocationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);

        new GnssMeasurementsEvent.Callback() {
            @Override
            public void onGnssMeasurementsReceived(GnssMeasurementsEvent event) {
                event.getMeasurements();

            }
        };
        mGnssStatusCallback = new GnssStatus.Callback() {
            @Override
            public void onSatelliteStatusChanged(GnssStatus status) {
                if(getActivity()!=null) {
                    int numberGps = 0;
                    int numberGlonass = 0;
                    int numberSatellites = status.getSatelliteCount();
                    for (int i = 0; i < numberSatellites; i++) {
                        if (status.getConstellationType(i) == GnssStatus.CONSTELLATION_GPS || status.getConstellationType(i) == GnssStatus.CONSTELLATION_GLONASS ) {
                            numberGps++;
                        } else if (status.getConstellationType(i) == GnssStatus.CONSTELLATION_GLONASS) {
                            numberGlonass++; 
                    }
                    String numberOfSatellites = getString(R.string.number_of_satelites) + numberSatellites + ".\n\n";
                    cn0/=numberGps;
                    String numberOfGps = getString(R.string.number_of_gps) + numberGps + " and Cn0 = "+cn0+".\n\n";
                    String numberOfGlonass = getString(R.string.number_of_glonass) + numberGlonass + ".";
                    numberSatellitesTextView.setText(numberOfSatellites + numberOfGps + numberOfGlonass);
                    isLoadingProgress = false;
                    gnssError = ErrorTest.TEST_WORKING;
                }
            }
            @Override
            public void onStarted(){
            }
            @Override
            public void onStopped(){
            }

        };

        return view;
    }

    @Override
    public void onStart() {
        super.onStart();
        requestLocation();

    }

    private void requestLocation() {
        if (mContext.checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_LOCATION);
        }
        else if(!mLocationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
                createDialogActivateGPSProvider();
        }
        else {
            mLocationManager.registerGnssStatusCallback(mGnssStatusCallback,new Handler(Looper.getMainLooper()));
            mLocationManager.registerGnssMeasurementsCallback(gnssMeasurementsEventListener);
            mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 30000, 0, this);
        }
    }


    @Override
    public void onStop() {
        mLocationManager.removeUpdates(this);
        mLocationManager.unregisterGnssStatusCallback(mGnssStatusCallback);
        mLocationManager.unregisterGnssMeasurementsCallback(gnssMeasurementsEventListener);
        super.onStop();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

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

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

}

有时（大多数情况下），它运行良好，我可以看到流向方法onSatelliteStatusChanged的流程，但是有时，它却从未流向该方法（位置设置为on）。 你知道为什么吗？