Question

我在尝试在空对象引用上调用虚方法NullPointerException时获得double android.location.Location.getLatitude()。

我正在使用解析服务器（back4app.com）。花费数小时试图找出问题可以帮到任何人。

提前谢谢

package carsharing.com.carre;

import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Address;
import android.location.Criteria;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

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.maps.model.MarkerOptions;
import com.parse.FindCallback;
import com.parse.ParseACL;
import com.parse.ParseException;
import com.parse.ParseGeoPoint;
import com.parse.ParseObject;
import com.parse.ParseQuery;
import com.parse.ParseUser;
import com.parse.SaveCallback;

import java.io.IOException;
import java.util.List;
import java.util.Locale;

import static carsharing.com.carre.R.id.map;

public class YourLocation extends FragmentActivity implements OnMapReadyCallback, LocationListener {

    private GoogleMap mMap;
    LocationManager locationManager;
    String provider;
    TextView information;
    Location location;
    Button requestRide;
    Boolean requestActive = false;
    Handler handler = new Handler();
    ParseGeoPoint driverLocation = new ParseGeoPoint(0, 0);
    Double lat;
    Double lng;
    String driverUsername = "";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_your_location);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(map);
        mapFragment.getMapAsync(this);

        information = (TextView) findViewById(R.id.information);
        requestRide = (Button) findViewById(R.id.requestRide);

        //Use the location manager and provider to determine the users location accurate to 1 meter, updated 400 miliseconds
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        provider = locationManager.getBestProvider(new Criteria(), false);
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        locationManager.requestLocationUpdates(provider, 400, 1, this);
    }

    public void updateUserLocation(final Location location) {
        lat = location.getLatitude();


        lng = location.getLongitude();

        mMap.addMarker(new MarkerOptions()
                .position(new LatLng(lat, lng)).title("Your location"));
        mMap.animateCamera(CameraUpdateFactory
                .newLatLngZoom(new LatLng(lat, lng), 10));


        if (!requestActive) {

            ParseQuery<ParseObject> query = new ParseQuery<>("requests");

            query.whereEqualTo("riderUsername", ParseUser.getCurrentUser().getUsername());

            query.findInBackground(new FindCallback<ParseObject>() {
                @Override
                public void done(List<ParseObject> objects, ParseException e) {

                    if (e == null) {

                        if (objects.size() > 0) {

                            for (ParseObject object : objects) {

                                requestActive = true;
                                information.setText(R.string.findingDriver);
                                requestRide.setText(R.string.cancelR);

                                if (object.get("driverUsername") != null) {

                                    driverUsername = object.getString("driverUsername");
                                    information.setText(R.string.onTheWay);

                                    Log.i("AppInfo", driverUsername);

                                }

                            }

                        }

                    }

                }
            });
        }
        if (requestActive) {

            if (!driverUsername.equals("")) {

                ParseQuery<ParseUser> userQuery = ParseUser.getQuery();
                userQuery.whereEqualTo("username", driverUsername);
                userQuery.findInBackground(new FindCallback<ParseUser>() {
                    @Override
                    public void done(List<ParseUser> objects, ParseException e) {
                        if (e == null) {
                            if (objects.size() > 0) {

                                for (ParseUser driver : objects) {

                                    driverLocation = driver.getParseGeoPoint("location");

                                }

                            }
                        }
                    }
                });

                if (driverLocation.getLatitude() != 0 && driverLocation.getLongitude() != 0) {
                    Log.i("AppInfo", driverLocation.toString());
                }

            }

            final ParseGeoPoint userLocation = new ParseGeoPoint(lat, lng);

            ParseQuery<ParseObject> query = new ParseQuery<>("requests");

            query.whereEqualTo("riderUsername", ParseUser.getCurrentUser().getUsername());

            query.findInBackground(new FindCallback<ParseObject>() {
                @Override
                public void done(List<ParseObject> objects, ParseException e) {

                    if (e == null) {

                        if (objects.size() > 0) {

                            for (ParseObject object : objects) {

                                object.put("riderLocation", userLocation);
                                object.saveInBackground();

                            }

                        }

                    }

                }
            });

        }

        /*
          Causes the Runnable in this thread to be run each 2000 milliseconds, updating location.
         */
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                updateUserLocation(location);
            }
        }, 2000);

    }


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


    @Override
    protected void onResume() {
        super.onResume();
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        locationManager.requestLocationUpdates(provider, 400, 1, this);
    }

    //pauses location search when the user closes the app to save on battery
    @Override
    protected void onPause() {
        super.onPause();
        locationManager.removeUpdates(this);
    }


    @Override
    public void onLocationChanged(Location location) {
        /*if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

        lat = location.getLatitude();
        lng = location.getLongitude();

        mMap.clear();
        updateUserLocation(location);
        getAddress();
    }




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

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }

    public void getAddress() {
        Geocoder geocoder = new Geocoder(getApplicationContext(), Locale.getDefault());

        try {

            List<Address> listAddresses = geocoder.getFromLocation(lat, lng, 1);

            if (listAddresses != null && listAddresses.size() > 0) {

                Log.i("Location Info:", listAddresses.get(0).toString());

            }

        } catch (IOException e) {

            e.printStackTrace();

        }
    }
    //when request ride
    public void requestRide(View view) {
        //Allows the user to create a request
        if (!requestActive) {

            final ParseObject request = new ParseObject("requests");

            request.put("riderUsername", ParseUser.getCurrentUser().getUsername());

            ParseACL parseACL = new ParseACL();
            parseACL.setPublicWriteAccess(true);
            parseACL.setPublicReadAccess(true);
            request.setACL(parseACL);

            request.saveInBackground(new SaveCallback() {
                @Override
                public void done(ParseException e) {

                    if (e == null) {

                        updateUserLocation(location);

                        information.setText(R.string.info);
                        requestRide.setText(R.string.rideRequest);
                        requestActive = true;

                    }

                }
            });

        } else {

            ParseQuery<ParseObject> query = new ParseQuery<>("requests");

            query.whereEqualTo("riderUsername", ParseUser.getCurrentUser().getUsername());

            query.findInBackground(new FindCallback<ParseObject>() {
                @Override
                public void done(List<ParseObject> objects, ParseException e) {

                    if (e == null) {

                        if (objects.size() > 0) {

                            for (ParseObject object : objects) {

                                object.deleteInBackground();

                            }

                        }

                    }

                }
            });

            information.setText(R.string.infoCancelR);
            requestRide.setTeenter code herext(R.string.RequestRide);
            requestActive = false;

        }

    }
}

除外的原因

public void updateUserLocation（final location location）{ lat = location.getLatitude（）; lng = location.getLongitude（）;

    mMap.addMarker(new MarkerOptions()
            .position(new LatLng(lat, lng)).title("Your location"));
    mMap.animateCamera(CameraUpdateFactory
            .newLatLngZoom(new LatLng(lat, lng), 10));


    if (!requestActive) {

        ParseQuery<ParseObject> query = new ParseQuery<>("requests");

        query.whereEqualTo("riderUsername", ParseUser.getCurrentUser().getUsername());

        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> objects, ParseException e) {

                if (e == null) {

                    if (objects.size() > 0) {

                        for (ParseObject object : objects) {

                            requestActive = true;
                            information.setText(R.string.findingDriver);
                            requestRide.setText(R.string.cancelR);

                            if (object.get("driverUsername") != null) {

                                driverUsername = object.getString("driverUsername");
                                information.setText(R.string.onTheWay);

                                Log.i("AppInfo", driverUsername);

                            }

                        }

                    }

                }

            }
        });
    }
    if (requestActive) {

        if (!driverUsername.equals("")) {

            ParseQuery<ParseUser> userQuery = ParseUser.getQuery();
            userQuery.whereEqualTo("username", driverUsername);
            userQuery.findInBackground(new FindCallback<ParseUser>() {
                @Override
                public void done(List<ParseUser> objects, ParseException e) {
                    if (e == null) {
                        if (objects.size() > 0) {

                            for (ParseUser driver : objects) {

                                driverLocation = driver.getParseGeoPoint("location");

                            }

                        }
                    }
                }
            });

            if (driverLocation.getLatitude() != 0 && driverLocation.getLongitude() != 0) {
                Log.i("AppInfo", driverLocation.toString());
            }

        }

        final ParseGeoPoint userLocation = new ParseGeoPoint(lat, lng);

        ParseQuery<ParseObject> query = new ParseQuery<>("requests");

        query.whereEqualTo("riderUsername", ParseUser.getCurrentUser().getUsername());

        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> objects, ParseException e) {

                if (e == null) {

                    if (objects.size() > 0) {

                        for (ParseObject object : objects) {

                            object.put("riderLocation", userLocation);
                            object.saveInBackground();

                        }

                    }

                }

            }
        });

    }

    /*
      Causes the Runnable in this thread to be run each 2000 milliseconds, updating location.
     */
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            updateUserLocation(location);
        }
    }, 2000);

}

logcat的

Answer 1

没有初始化位置尝试在

中初始化它

    @Override
    public void onLocationChanged(Location location) {
         this.location=location;
    }

Answer 2

您正在尝试访问未初始化或为空的位置。在 updateUserLocation（）

中添加另一个空指针检查

public void updateUserLocation(final Location location) {
        if (location.getLatitude()!=null && location.getLongitude()!=null)
        {
        lat = location.getLatitude();
        lng = location.getLongitude();
        }

}

java.lang.NullPointerException：尝试在空对象引用上调用虚方法'double android.location.Location.getLatitude（）'

2 个答案: