kann den Standort nicht der Länge eine Breite

Question

Wenn ich versuche, meinen Code auszuführen, habe ich immer diese Fehlermeldung erhalten:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

ich manuell die Koordinaten in meinem Emulator konfigurieren können, aber immer noch, bekam den gleichen Fehler.

Hier sind meine Codes zum Abrufen von Standortkoordinaten.

LocationTracker.java

public class LocationTracker extends MainActivity implements LocationListener { 
    MainActivity activity; 
    Context context; 
    Location location; 
    LocationManager lm; 

    double lat,longi; 


    boolean isGpsEnabled = false; 
    boolean isNetworkEnabled = false; 
    boolean canGetNetworkLocation = false; 

    public LocationTracker (Context context) { 
     this.context=context; 
     getGPSLocation(); 
    } 


    public Location getGPSLocation() { 

     lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE); 
     isGpsEnabled = lm.isProviderEnabled(LocationManager.GPS_PROVIDER); 


     if (isGpsEnabled) { 

      /** Check for RUNTIME PERMISSION */ 
      if (ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED || ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) { 

       if (location == null) {  //Request for NEW DATA coming from GPS 
        lm.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,this); 

        if (lm != null) { //Retrieve data from the earlier 
         location=lm.getLastKnownLocation(LocationManager.GPS_PROVIDER); 

         if (location != null) { 
          lat= location.getLatitude(); 
          longi= location.getLongitude(); 
         } 
        } 
       } 



      }else { 
       ActivityCompat.requestPermissions(activity,new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION},123); 
      } 

     }else { 

     } 

    return location; 
     } 

    /** GET LATITUDE METHOD */ 
     public double getLatitude() { 
      if (location != null) { 
       lat=location.getLatitude(); 
      } 

      return lat; 
     } 

    /** GET LONGITUDE METHOD */ 
     public double getLongitude() { 
      if (location != null) { 
       longi=location.getLongitude(); 
      } 
      return longi; 
     } 

    @Override 
    public void onLocationChanged(Location location) { 
     lat= location.getLatitude(); 
     longi=location.getLongitude(); 
    } 

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

    } 

    @Override 
    public void onProviderEnabled(String provider) { 

    } 

    @Override 
    public void onProviderDisabled(String provider) { 

    } 
} 

und MainActivity Klasse für Koordinaten anzeigt.

public class MainActivity extends AppCompatActivity { 
Context context; 
DBHelper helper; 
LocationTracker tracker; 



TextView contactsTv,sendEmergencyTv; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    helper=new DBHelper(getApplicationContext()); 


    /** 
    * OnClick Listener in android 
     */ 
    contactsTv=(TextView) findViewById(R.id.tv_createContacts); 
    contactsTv.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent intent= new Intent(MainActivity.this, ContactsActivity.class); //redirect to the COntacts dsadsadsa 

      startActivity(intent); 
     } 
    }); 

sendEmergencyTv=(TextView)findViewById(R.id.tv_sendEmergency); 
    sendEmergencyTv.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      tracker= new LocationTracker(MainActivity.this); 
      double lat,longi; 

      lat= tracker.getLatitude(); 
      longi= tracker.getLongitude(); 

      Toast.makeText(context,"Latitude: "+lat+ "Longitude: "+longi,Toast.LENGTH_LONG).show(); 
     } 
    }); 
} 

} 

By the way, ich bin nicht sicher im requestPermission Parameter eine MainActivity Instanz innerhalb der LocationTracker Klasse zu platzieren.

Answer 1

hier:

ActivityCompat.requestPermissions(activity, 
      new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, 
         Manifest.permission.ACCESS_FINE_LOCATION},123); 

Linie verursacht Problem, weil activitynull ist.

Verwenden ((Activity)context) statt activity .like:

ActivityCompat.requestPermissions(((Activity)context), 
      new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, 
         Manifest.permission.ACCESS_FINE_LOCATION},123); 

HINWEIS:

Auch, weil LocationTracker eine normale Java-Klasse ist so keine Notwendigkeit, sich Activity darin.

Answer 2

In der Zeile

ActivityCompat.requestPermissions(activity, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION},123); 

activity ist null, da es nie ein Wert zugewiesen wurde.

Ändern Sie den LocationTracker Konstruktor, um Activity anstelle von Context als Parameter zu übernehmen.

private Activity activity; 

public LocationTracker (Activity activity) { 
    this.activity = activity; 
    getGPSLocation(); 
} 

NB: Stellen Sie sicher, dass Sie onRequestPermissionsResult in dieser Tätigkeit umsetzen wissen, ob Sie die Berechtigungen oder nicht erteilt habe.