Locationlistener est null

Question

L'erreur vient en raison de l'emplacement de l'écouteur est null.J'ai mis l'écouteur de localisation dans le JsonObjectRequest de volley bibliothèque. mon code est

protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_maps); 
     // 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); 
     mLocationManager = (LocationManager) getSystemService(LOCATION_SERVICE); 

     if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
      // TODO: Consider calling 
      // ActivityCompat#requestPermissions 
      // here to request the missing permissions, and then overriding 
      // public void onRequestPermissionsResult(int requestCode, String[] permissions, 
      //           int[] grantResults) 
      // to handle the case where the user grants the permission. See the documentation 
      // for ActivityCompat#requestPermissions for more details. 
      return; 
     } 
     mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 500, 1, mLocationListener); 

    } 


    /** 
    * 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.setMyLocationEnabled(true); 
     // Add a marker in Sydney and move the camera 
     UiSettings uiSettings=mMap.getUiSettings(); 
     uiSettings.setZoomControlsEnabled(true); 
     //mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney)); 
     requestQueue= Volley.newRequestQueue(this); 
     JsonObjectRequest jsonObjectRequest=new JsonObjectRequest(Request.Method.GET, loginUrl, new Response.Listener<JSONObject>() { 
      @Override 
      public void onResponse(JSONObject response) { 

       try { 
        JSONArray ja = response.getJSONArray("hi"); 
        retid= new String[ja.length()]; 
        retph= new String[ja.length()]; 
        retname=new String[ja.length()]; 
        retlat= new Double[ja.length()]; 
        retlong= new Double[ja.length()]; 
        for(int i=0;i<ja.length();i++){ 
         JSONObject jsonObject=ja.getJSONObject(i); 
         if(!(jsonObject.getString("retailer_loc_lat").equals("0")&&jsonObject.getString("retailer_loc_long").equals("0"))) { 
          retid[i] = jsonObject.getString("retailer_id") + ""; 
          retname[i] = jsonObject.getString("retailer_first_name") + " " + jsonObject.getString("retailer_last_name"); 
          retlat[i] = Double.parseDouble(jsonObject.getString("retailer_loc_lat")); 
          retlong[i] = Double.parseDouble(jsonObject.getString("retailer_loc_long")); 
          retph[i] = "Phone:" + jsonObject.getString("retailer_ph_no"); 

         } 
        } 

        mLocationListener = new LocationListener() { 
           @Override 
           public void onLocationChanged(final Location location) { 
            for(int j=0;j<retid.length;j++){ 
             if(almostEqual(retlat[j],location.getLatitude(),.5)&&almostEqual(retlong[j],location.getLatitude(),.5)){ 
              mMap.addMarker(new MarkerOptions().position(new LatLng(retlat[j], retlong[j])).title(retname[j]).snippet(retph[j]).icon(BitmapDescriptorFactory.fromResource(R.drawable.map_pin_96))); 
             } 
            } 

           } 

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

           } 

           @Override 
           public void onProviderEnabled(String provider) { 

           } 

           @Override 
           public void onProviderDisabled(String provider) { 

           } 
          }; 


       } catch (JSONException e) { 
        e.printStackTrace(); 
       } 
      } 
     }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 

      } 
     });requestQueue.add(jsonObjectRequest); 

    } 

mon chat journal

Caused by: java.lang.IllegalArgumentException: invalid listener: null 
                    at android.location.LocationManager.checkListener(LocationManager.java:1606) 
                    at android.location.LocationManager.requestLocationUpdates(LocationManager.java:426) 

La raison principale est que le gestionnaire de l'emplacement ne peut pas obtenir l'emplacement d'écoute à la JsonObjectRequest. S'il vous plaît aider.

Answer 1

mapFragment.getMapAsync(this); est un appel asynchrone non bloquant. Par conséquent
mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 500, 1, mLocationListener);
est exécutée avant d'obtenir le rappel onMapReady(). Maintenant que mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 500, 1, mLocationListener); est exécuté avant onMapReady(), mLocationListener est nul puisque vous ne l'avez pas initialisé auparavant. Et c'est pourquoi vous obtenez une exception.

Answer 2

@Override 
public void onMapReady(GoogleMap googleMap) { 
    ... 
    JsonObjectRequest jsonObjectRequest=new JsonObjectRequest(Request.Method.GET, loginUrl, new Response.Listener<JSONObject>() { 
     @Override 
     public void onResponse(JSONObject response) { 
       ... 
       mLocationListener = new LocationListener() { 
        ... 
       }; 
       mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 500, 1, mLocationListener); 
       ...