android : 위치가 null 객체 참조 오류를 반환합니다.

Question

사용자의 위치, 특히 도시를 가져 오려고합니다. 앱이 런타임에 권한을 요청합니다. 그러나 위치를 ArrayList에 넣으려고하면 null 객체 참조 오류가 발생합니다.

아래에서 구체적인 내용을 말씀 드리겠습니다.

내가 뭘 잘못하고 있니?

ERROR 널 객체 참조에 '를 java.util.List android.location.Geocoder.getFromLocation (더블 더블 INT)'의 가상 메소드를 호출

시도

import android.Manifest; 
import android.content.Context; 
import android.content.DialogInterface; 
import android.content.Intent; 
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.provider.Settings; 
import android.support.v4.app.ActivityCompat; 
import android.support.v4.content.ContextCompat; 
import android.support.v7.app.AlertDialog; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.util.Log; 
import android.widget.TextView; 

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

public class PhoneList extends AppCompatActivity implements LocationListener { 


    LocationManager locationManager; 
    private String provider; 
    public final static int MY_PERMISSIONS_REQUEST_READ_LOCATION = 1; 
    public double myLng; 
    public double myLat; 
    List addresses = new ArrayList(); 

    public Geocoder myGeo; 

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

     if (1 == 0) { 
      showAlert(); 
     } else { 
      locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
      Criteria criteria = new Criteria(); 
      provider = locationManager.getBestProvider(criteria, false); 
      if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
       GetLocationPermission(); 

       return; 
      } 
      locationManager.requestLocationUpdates(provider, 0, 0, this); 
      Location location = locationManager.getLastKnownLocation(provider); 
      onLocationChanged(location); 

      myLat = location.getLatitude(); 
      myLng = location.getLongitude(); 
     } 

    } 

    private void showAlert() { 
     final AlertDialog.Builder dialog = new AlertDialog.Builder(this); 
     dialog.setTitle("Enable Location") 
       .setMessage("Your Locations Settings is set to 'Off'.\nPlease Enable Location to " + 
         "use this app") 
       .setPositiveButton("Location Settings", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface paramDialogInterface, int paramInt) { 
         Intent myIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
         startActivity(myIntent); 
        } 
       }) 
       .setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface paramDialogInterface, int paramInt) { 
        } 
       }); 
     dialog.show(); 
    } 

    public void GetLocationPermission(){ 
     if (ContextCompat.checkSelfPermission(this, 
       Manifest.permission.ACCESS_FINE_LOCATION) 
       != PackageManager.PERMISSION_GRANTED) { 
      ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, MY_PERMISSIONS_REQUEST_READ_LOCATION); 
     } 
    } 

    @Override 
    public void onRequestPermissionsResult(int requestCode, 
              String permissions[], int[] grantResults) { 
     switch (requestCode) { 
      case MY_PERMISSIONS_REQUEST_READ_LOCATION: { 
       // If request is cancelled, the result arrays are empty. 
       if (grantResults.length > 0 
         && grantResults[0] == PackageManager.PERMISSION_GRANTED) { 
        System.out.println("Yes"); 
       } else { 

        System.out.println("boo"); 
       } 
       return; 
      } 
     } 
    } 

    @Override 
    public void onLocationChanged(Location location) { 
     try { 

//ERROR IS ON THIS LINE 
      addresses = myGeo.getFromLocation(location.getLatitude(), location.getLongitude(), 10); 

     } catch (IOException e) { 
      Log.e("LocateMe", "Could not get Geocoder data", e); 

     } 
    } 

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

    } 

    @Override 
    public void onProviderEnabled(String provider) { 

    } 

    @Override 
    public void onProviderDisabled(String provider) { 

    } 
} 

Answer 1

룩 myGeo 참조를 초기화하지 않으 셨습니다.

수정하려면 getFromLocation()으로 전화하기 전에 초기화하십시오. 부수적으로, locationManager.getLastKnownLocation() 호출은 null을 반환 할 가능성이 있기 때문에 Location이 null이 아닌지도 확인해야합니다.

@Override 
public void onLocationChanged(Location location) { 
    try { 
     //Add initialization: 
     myGeo = new Geocoder(this, Locale.getDefault()); 
     //Make sure that the Location is not null: 
     if (location != null) { 
      addresses = myGeo.getFromLocation(location.getLatitude(), location.getLongitude(), 10); 
     } 

    } catch (IOException e) { 
     Log.e("LocateMe", "Could not get Geocoder data", e); 

    } 
}