我有谷歌地图活动，到目前为止工作正常。我不知道发生了什么，但是当调用“getLastKnownLocation”时应用程序崩溃了。我不明白为什么会发生这种情况，正如我之前所说，它一直运作到现在为止。
这是我得到的错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
这是我的地图活动：
public class MapActivity extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
LocationManager locationManager;
LocationListener locationListener;
private DatabaseReference mDatabase;
private FirebaseAuth mAuth;
private ArrayList<User> userArrayList = new ArrayList<>();
private User useri;
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == 1) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
{
locationManager.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 0, 0, locationListener);
}
}
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map);
// 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);
mDatabase = FirebaseDatabase.getInstance().getReference();
mAuth = FirebaseAuth.getInstance();
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
mMap.setMyLocationEnabled(true);
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
locationListener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
LatLng userLocation = new LatLng(location.getLatitude(), location.getLongitude());
mMap.clear();
mMap.addMarker(new MarkerOptions().position(userLocation).title("המיקום שלי"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(userLocation));
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
}
};
if (Build.VERSION.SDK_INT < 23) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
} else {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
}
else {
mMap.setMyLocationEnabled(true);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
Location lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
LatLng userLocation = new LatLng(lastKnownLocation.getLatitude(), lastKnownLocation.getLongitude());
mDatabase.child("Users").child(mAuth.getCurrentUser().getUid()).child("lat").setValue(lastKnownLocation.getLatitude());
mDatabase.child("Users").child(mAuth.getCurrentUser().getUid()).child("lng").setValue(lastKnownLocation.getLongitude());
mMap.clear();
mMap.addMarker(new MarkerOptions().position(userLocation).title("המיקום שלי"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(userLocation));
}
}
showUsersOnMap();
}
// Search for location and show it on the map
public void onClick(View view) {
if(view.getId() == R.id.searchLocationBtn){
EditText searchBoxLocation = (EditText) findViewById(R.id.searchBoxLocation);
String location = searchBoxLocation.getText().toString();
List<Address> addressList = null;
MarkerOptions markerOptions = new MarkerOptions();
if( ! location.equals("")){
Geocoder geocoder = new Geocoder(this);
try {
addressList = geocoder.getFromLocationName(location, 1);
} catch (IOException e) {
e.printStackTrace();
}
for (int i = 0 ; i < addressList.size(); i++){
Address myAddress = addressList.get(i);
LatLng latLng = new LatLng(myAddress.getLatitude(), myAddress.getLongitude());
markerOptions.position(latLng);
mMap.clear();
mMap.addMarker(markerOptions);
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng,11));
searchBoxLocation.setText("");
}
}
}
showUsersOnMap();
}
// Function to show all the users on the map
public void showUsersOnMap(){
mDatabase.child("Users").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds: dataSnapshot.getChildren()){
User user = ds.getValue(User.class);
userArrayList.add(user);
}
for (int i = 0; i < userArrayList.size(); i++) {
useri = userArrayList.get(i);
if (useri.getLat() != 0 && useri.getLng() != 0) {
MarkerOptions markerOptions = new MarkerOptions();
LatLng userlatLng = new LatLng(useri.getLat(), useri.getLng());
markerOptions.position(userlatLng);
mMap.addMarker(new MarkerOptions().position(userlatLng).title(useri.getName()).snippet(useri.getPhone())
.icon(BitmapDescriptorFactory.fromResource(R.drawable.ic_action_marker2)));
//mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng2,10));
}
else Toast.makeText(getApplicationContext(),"ישנה בעיה. אנא נסה להתחבר למפה שוב",Toast.LENGTH_LONG).show();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
我希望有人能弄明白问题是什么。我搜索了同样的问题，但没有成功。
答案 0 :(得分：0)
将此行移至oncreate并检查
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);