Android-GeoFire项目上的位置NullPointerException错误

Question

刚刚适应Java和Android，并且遇到了以上错误。

[当我在应用程序上单击一个按钮，该按钮将寻找用户类型的“响应者”时触发。应用程序崩溃了，我得到了这个错误：

 java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
                      at com.jamesboyle.firsthelp.PatientMapActivity$2.onClick(PatientMapActivity.java:83)

我不确定此刻什么是空对象

mRequest.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    String userID = FirebaseAuth.getInstance().getCurrentUser().getUid();

                    DatabaseReference ref = FirebaseDatabase.getInstance().getReference("patientRequest");
                    GeoFire geoFire = new GeoFire(ref);
                    geoFire.setLocation(userID, new GeoLocation(mLastLocation.getLatitude(), mLastLocation.getLongitude()));

                    pickupLocation = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());
                    mMap.addMarker(new MarkerOptions().position(pickupLocation).title("Respond Now"));

                    mRequest.setText("Locating Responder...");

                    getClosestResponder();
                }
            });
        }
        private int radius =1;
        private Boolean responderFound = false;
        private String responderFoundID;
        private void getClosestResponder(){
            DatabaseReference responderLocation = FirebaseDatabase.getInstance().getReference().child("respondersAvailable");

            GeoFire geoFire = new GeoFire(responderLocation);

            GeoQuery geoQuery = geoFire.queryAtLocation(new GeoLocation(pickupLocation.latitude, pickupLocation.longitude), radius);
            geoQuery.removeAllListeners();

            geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
                @Override
                public void onKeyEntered(String key, GeoLocation location) {
                    if (!responderFound) {
                        responderFound = true;
                        responderFoundID = key;
                    }
                }

Answer 1

替换

pickupLocation = new LatLng(mLastLocation.getLatitude(),mLastLocation.getLongitude());` with `geoFire.setLocation("firebase-hq", new GeoLocation(37.7853889, -122.4056973));

有关详细信息和理解，请访问GeoFire for Java — Realtime location queries with Firebase