android - mFusedLocationProviderClient.getLastLocation() ，位置始终为空

Question

我正在尝试构建始终跟踪我的客户位置的应用程序，该应用程序始终显示该位置为空。在 Manifest 文件中，我拥有 (ACCESS_FINE_LOCATION) 和 (ACCESS_COARSE_LOCATION) 权限。

问题是每次我打开应用程序时，它都会显示 Toast 消息（ Location 为 null ），正如我在代码中所述，但我不知道获取 null 位置的原因是什么，即使我正在使用 (requestLocationUpdates ) (FusedLocationProviderClient) 类的方法..

import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.tasks.OnSuccessListener;

public class DriverMapActivity extends FragmentActivity implements OnMapReadyCallback {

    // constants
    private static final String TAG = "DriverMapActivity";
    private static final int MY_REQUEST_LOCATION_CODE = 101;

    // vars
    private GoogleMap mMap;
//    private boolean mLocationPermissionGranted = false;
    private FusedLocationProviderClient mFusedLocationProviderClient;
    private LocationRequest mLocationRequest;
    private LocationCallback mLocationCallback;
    private LatLng newLatLng;


    // vars


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_driver_map);

        // start receiving location updates
        getMyLocation();

        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

    }


    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;


        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return;
        }
        mMap.setMyLocationEnabled(true);
    }




    private void getMyLocation(){

        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(5000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);

        mFusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {

            // permission is granted
            // and we can now use getLastLocation method
            mFusedLocationProviderClient.getLastLocation().addOnSuccessListener(this, new OnSuccessListener<Location>() {
                @Override
                public void onSuccess(Location location) {
                    if (location != null) {
                        newLatLng = new LatLng(location.getLatitude(), location.getLongitude());

                        mMap.moveCamera(CameraUpdateFactory.newLatLng(newLatLng));
                        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

                        Log.d(TAG, "onSuccess: Latitude = " + location.getLatitude());
                        Log.d(TAG, "onSuccess: Longitude = " + location.getLongitude());
                    } else {
                        Toast.makeText(DriverMapActivity.this, "Location is null", Toast.LENGTH_SHORT).show();
                    }
                }
            });

        } else {

            // permission is not granted.
            // we have to request the user to grant the the ACCESS_FINE_LOCATION permission.
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, MY_REQUEST_LOCATION_CODE);
            }
        }

        mLocationCallback = new LocationCallback() {
            @Override
            public void onLocationResult(LocationResult locationResult) {
                super.onLocationResult(locationResult);

                for (Location location : locationResult.getLocations()) {

                    if (location != null) {
                        newLatLng = new LatLng(location.getLatitude(), location.getLongitude());

                        mMap.moveCamera(CameraUpdateFactory.newLatLng(newLatLng));
                        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

                        Log.d(TAG, "onSuccess: Latitude = " + location.getLatitude());
                        Log.d(TAG, "onSuccess: Longitude = " + location.getLongitude());
                    } else {
                        Toast.makeText(DriverMapActivity.this, "Location is null", Toast.LENGTH_SHORT).show();
                    }
                }

            }
        };
    }



    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        switch (requestCode) {

            case MY_REQUEST_LOCATION_CODE:
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    // permission has been granted and we can proceed with app

                } else {
                    Toast.makeText(this, "app closed because you didn't granted the required permission", Toast.LENGTH_SHORT).show();
                    finish();
                }

                break;
        }
    }


    private void startLocationUpdates() {

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {

            mFusedLocationProviderClient.requestLocationUpdates(mLocationRequest, mLocationCallback, null);

        }else{
            // permission is not granted.
            // we have to request the user to grant the the ACCESS_FINE_LOCATION permission.
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, MY_REQUEST_LOCATION_CODE);
            }
        }

    }

    private void stopLocationUpdates() {
        mFusedLocationProviderClient.removeLocationUpdates(mLocationCallback);
    }



    @Override
    protected void onResume() {
        super.onResume();
        startLocationUpdates();
    }



    @Override
    protected void onPause() {
        super.onPause();
        stopLocationUpdates();
    }

    @Override
    protected void onStop() {
        super.onStop();
        stopLocationUpdates();
    }





}

标签： androidfusedlocationproviderclient