Geocoder，locationName == null

Question

因此，我正在开发一个社交活动应用程序，用户可以发布活动并让人们在地图或列表中看到这些活动。我目前正在努力对我的数据库中的位置地址进行地理编码，并将其转换为经纬度坐标。我已经查看了几十次代码，并得到相同的错误。 “locationName == null”我得出的唯一结论是，我实际上并没有从数据库中提取任何数据，而是向给我这个错误的geocoder发送了null值。我正在使用Android Studio和Google Firestore作为我的数据库。希望有一些新鲜的眼睛可以让我对这个问题有所了解。如果您需要查看其他相关代码片段，请告知我们。

MainActivity.java

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback, GoogleMap.OnMyLocationButtonClickListener, ActivityCompat.OnRequestPermissionsResultCallback { 

private static final String TAG = MainActivity.class.getSimpleName(); 
private ImageButton notifyButton; 
private ImageButton messagesButton; 
private ImageButton exploreButton; 
private ImageButton profileButton; 

private double lat; 
private double lng; 
private String address; 
private String city; 
private String state; 
private int zipcode; 

private LatLng geoCoord; 

/** 
* Request code for location permission request. 
* 
* @see #onRequestPermissionsResult(int, String[], int[]) 
*/ 
private static final int LOCATION_PERMISSION_REQUEST_CODE = 1; 

/** 
* Flag indicating whether a requested permission has been denied after returning in 
* {@link #onRequestPermissionsResult(int, String[], int[])}. 
*/ 
private boolean mPermissionDenied = false; 

private GoogleMap mMap; 
private MarkerOptions options = new MarkerOptions(); 

private FirebaseFirestore db = FirebaseFirestore.getInstance(); 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.activity_main); 

    notifyButton = (ImageButton) findViewById(R.id.notifyButton); 
    notifyButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent main = new Intent(MainActivity.this, NotifyActivity.class); 
      startActivity(main); 
     } 
    }); 

    messagesButton = (ImageButton) findViewById(R.id.messagesButton); 
    messagesButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent main = new Intent(MainActivity.this, MessengerActivity.class); 
      startActivity(main); 
     } 
    }); 

    exploreButton = (ImageButton) findViewById(R.id.exploreButton); 
    exploreButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent main = new Intent(MainActivity.this, ExploreActivity.class); 
      startActivity(main); 
     } 
    }); 

    profileButton = (ImageButton) findViewById(R.id.profileButton); 
    profileButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent main = new Intent(MainActivity.this, ProfileActivity.class); 
      startActivity(main); 
     } 
    }); 



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


} 




/** 
* Manipulates the map once available. 
* This callback is triggered when the map is ready to be used. 
* This is where we can add markers or lines, add listeners or move the camera. In this case, 
* we just add a marker near Sydney, Australia. 
* If Google Play services is not installed on the device, the user will be prompted to install 
* it inside the SupportMapFragment. This method will only be triggered once the user has 
* installed Google Play services and returned to the app. 
*/ 
@Override 
public void onMapReady(GoogleMap googleMap) { 

    mMap = googleMap; 
    mMap.setOnMyLocationButtonClickListener(this); 
    enableMyLocation(); 


    try { 
     // Customise the styling of the base map using a JSON object defined 
     // in a raw resource file. 
     boolean success = googleMap.setMapStyle(
       MapStyleOptions.loadRawResourceStyle(
         this, R.raw.style_json)); 

     if (!success) { 
      Log.e(TAG, "Style parsing failed."); 
     } 
    } catch (Resources.NotFoundException e) { 
     Log.e(TAG, "Can't find style. Error: ", e); 
    } 
    // Position the map's camera near Sydney, Australia. 

    googleMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(-34, 151))); 
    googleMap.addMarker(new MarkerOptions().position(geoLocate())); 
} 

private void enableMyLocation() { 
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) 
      != PackageManager.PERMISSION_GRANTED) { 
     // Permission to access the location is missing. 
     PermissionUtils.requestPermission(this, LOCATION_PERMISSION_REQUEST_CODE, 
       Manifest.permission.ACCESS_FINE_LOCATION, true); 
    } else if (mMap != null) { 
     // Access to the location has been granted to the app. 
     mMap.setMyLocationEnabled(true); 
    } 
} 

@Override 
public boolean onMyLocationButtonClick() { 
    Toast.makeText(this, "Current Location", Toast.LENGTH_SHORT).show(); 
    // Return false so that we don't consume the event and the default behavior still occurs 
    // (the camera animates to the user's current position). 
    return false; 
} 


@Override 
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, 
             @NonNull int[] grantResults) { 
    if (requestCode != LOCATION_PERMISSION_REQUEST_CODE) { 
     return; 
    } 

    if (PermissionUtils.isPermissionGranted(permissions, grantResults, 
      Manifest.permission.ACCESS_FINE_LOCATION)) { 
     // Enable the my location layer if the permission has been granted. 
     enableMyLocation(); 
    } else { 
     // Display the missing permission error dialog when the fragments resume. 
     mPermissionDenied = true; 
    } 
} 

@Override 
protected void onResumeFragments() { 
    super.onResumeFragments(); 
    if (mPermissionDenied) { 
     // Permission was not granted, display error dialog. 
     showMissingPermissionError(); 
     mPermissionDenied = false; 
    } 
} 

/** 
* Displays a dialog with error message explaining that the location permission is missing. 
*/ 
private void showMissingPermissionError() { 
    PermissionUtils.PermissionDeniedDialog 
      .newInstance(true).show(getSupportFragmentManager(), "dialog"); 
} 

public LatLng geoLocate() { 
    Geocoder gc = new Geocoder(this); 
    List <Address> list; 
    try{ 
     list = gc.getFromLocationName(getFullAddress(), 1); 
    } 
    catch (IOException e) { 

     return null; 
    } 
    Address add = list.get(0); 
    String locality = add.getLocality(); 
    Toast.makeText(this, locality, Toast.LENGTH_LONG).show(); 

    return new LatLng(add.getLatitude(), add.getLongitude()); 

} 

public String getFullAddress() { 
    DocumentReference docRef = db.collection("events").document("House Party"); 
    docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() { 
     @Override 
     public void onSuccess(DocumentSnapshot documentSnapshot) { 
      Event event = documentSnapshot.toObject(Event.class); 
      address = event.getAddress() + ", " + event.getCity() + ", " + event.getState() + " " + event.getZipcode(); 
     } 
    }); 
    return address; 
} 

}

错误日志

FATAL EXCEPTION: main 
                    Process: com.example.android.gathr, PID: 8599 
                    java.lang.IllegalArgumentException: locationName == null 
                     at android.location.Geocoder.getFromLocationName(Geocoder.java:171) 
                     at com.example.android.gathr.MainActivity$override.geoLocate(MainActivity.java:232) 
                     at com.example.android.gathr.MainActivity$override.access$dispatch(MainActivity.java) 
                     at com.example.android.gathr.MainActivity.geoLocate(MainActivity.java:0) 
                     at com.example.android.gathr.MainActivity$override.onMapReady(MainActivity.java:169) 
                     at com.example.android.gathr.MainActivity$override.access$dispatch(MainActivity.java) 
                     at com.example.android.gathr.MainActivity.onMapReady(MainActivity.java:0) 
                     at com.google.android.gms.maps.zzak.zza(Unknown Source) 
                     at com.google.android.gms.maps.internal.zzaq.onTransact(Unknown Source) 
                     at android.os.Binder.transact(Binder.java:507) 
                     at gl.b(:[email protected]:20) 
                     at com.google.android.gms.maps.internal.bf.a(:[email protected]:5) 
                     at com.google.maps.api.android.lib6.impl.bc.run(:[email protected]:5) 
                     at android.os.Handler.handleCallback(Handler.java:751) 
                     at android.os.Handler.dispatchMessage(Handler.java:95) 
                     at android.os.Looper.loop(Looper.java:154) 
                     at android.app.ActivityThread.main(ActivityThread.java:6642) 
                     at java.lang.reflect.Method.invoke(Native Method) 
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468) 
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358) 

编辑：

DocumentReference docRef = db.collection("cities").document("BJ"); 
docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() 
{ 
    @Override 
    public void onSuccess(DocumentSnapshot documentSnapshot) { 
    City city = documentSnapshot.toObject(City.class); 
    } 
    }); 

因此，我将数据保存为数据库中的对象，并根据上述代码从数据库中提取数据。我将地址元素存储在一个地址变量中，并让geolocate方法将该代码转换为经纬度坐标。

Answer 1

在getFullAddress()你叫什么，我认为是一个异步操作（docRef.get()）设置address但你立即返回address无需等待您加入到执行的监听器。

为了解决这个问题，您可以将地理编码移动到onSuccess回调中，如果文档检索工作正常，那么只有在执行地理编码时会产生很好的副作用。