App stürzt ab, wenn ich die Serviceabsicht

Question

anrufen

Ich fange an, Dienste in Android zu lernen und für das aktuelle Projekt möchte ich den Standort im Hintergrund verfolgen, auch wenn App geschlossen ist, aber wenn ich die Absicht für den Dienst aus rufe Die Hauptaktivität stürzt die ganze App ab. Ich habe diesen Service:

import android.app.Service; 
import android.content.Context; 
import android.content.Intent; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.location.Location; 
import android.location.LocationManager; 
import android.os.Bundle; 
import android.os.IBinder; 
import android.util.Log; 
import android.widget.Toast; 


/** 
* Created by Gurchani on 4/21/2017. 
*/ 

public class service extends Service { 
    private static final String TAG = "BOOMBOOMTESTGPS"; 
    private LocationManager mLocationManager = null; 
    private static final int LOCATION_INTERVAL = 1000; 
    private static final float LOCATION_DISTANCE = 10f; 
    private localDatabase database; 
    SQLiteDatabase db; 
    private double UserLong; 
    private double UserLat; 

    private class LocationListener implements android.location.LocationListener 
    { 
     Location mLastLocation; 

     public LocationListener(String provider) 
     { 
      Log.e(TAG, "LocationListener " + provider); 
      mLastLocation = new Location(provider); 
      makeToast(); 
     } 

     @Override 
     public void onLocationChanged(Location location) 
     { 
      Log.e(TAG, "onLocationChanged: " + location); 
      mLastLocation.set(location); 
      UserLat = mLastLocation.getLatitude(); 
      UserLong = mLastLocation.getLongitude(); 
      makeToast(); 
      doSQLQuery(); 
     } 

     @Override 
     public void onProviderDisabled(String provider) 
     { 
      Log.e(TAG, "onProviderDisabled: " + provider); 
     } 

     @Override 
     public void onProviderEnabled(String provider) 
     { 
      Log.e(TAG, "onProviderEnabled: " + provider); 
     } 

     @Override 
     public void onStatusChanged(String provider, int status, Bundle extras) 
     { 
      Log.e(TAG, "onStatusChanged: " + provider); 
     } 
    } 

    private void makeToast() { 
     Toast.makeText(this,"its on baby", Toast.LENGTH_LONG).show(); 
    } 

    private int doSQLQuery() { 
     double distance = 0.1; 

     // Define a projection that specifies which columns from the database 
     // you will actually use after this query. 
     String[] projection = { 
       FeederClass.FeedEntry.barId, 
     }; 

     // Filter results WHERE "title" = 'My Title' 
     Cursor c = dis(String.valueOf(Math.cos((double) distance/(double) 6380)), Math.cos(deg2rad(UserLat)), Math.sin(deg2rad(UserLat)), Math.cos(deg2rad(UserLong)), Math.sin(deg2rad(UserLong))); 
     Toast.makeText(this,"Your message.", Toast.LENGTH_LONG).show(); 
     return c.getCount(); 

    } 

    LocationListener[] mLocationListeners = new LocationListener[] { 
      new LocationListener(LocationManager.GPS_PROVIDER), 
      new LocationListener(LocationManager.NETWORK_PROVIDER) 
    }; 

    @Override 
    public IBinder onBind(Intent arg0) 
    { 
     return null; 
    } 

    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) 
    { 
     Log.e(TAG, "onStartCommand"); 
     super.onStartCommand(intent, flags, startId); 
     return START_STICKY; 
    } 

    @Override 
    public void onCreate() 
    { 
     Log.e(TAG, "onCreate"); 
     initializeLocationManager(); 
     db = database.getReadableDatabase(); 

     try { 
      mLocationManager.requestLocationUpdates(
        LocationManager.NETWORK_PROVIDER, LOCATION_INTERVAL, LOCATION_DISTANCE, 
        mLocationListeners[1]); 

     } catch (java.lang.SecurityException ex) { 
      Log.i(TAG, "fail to request location update, ignore", ex); 
     } catch (IllegalArgumentException ex) { 
      Log.d(TAG, "network provider does not exist, " + ex.getMessage()); 
     } 
     try { 
      mLocationManager.requestLocationUpdates(
        LocationManager.GPS_PROVIDER, LOCATION_INTERVAL, LOCATION_DISTANCE, 
        mLocationListeners[0]); 
     } catch (java.lang.SecurityException ex) { 
      Log.i(TAG, "fail to request location update, ignore", ex); 
     } catch (IllegalArgumentException ex) { 
      Log.d(TAG, "gps provider does not exist " + ex.getMessage()); 
     } 
    } 


    @Override 
    public void onDestroy() 
    { 
     Log.e(TAG, "onDestroy"); 
     super.onDestroy(); 
     if (mLocationManager != null) { 
      for (int i = 0; i < mLocationListeners.length; i++) { 
       try { 
        mLocationManager.removeUpdates(mLocationListeners[i]); 
       } catch (Exception ex) { 
        Log.i(TAG, "fail to remove location listners, ignore", ex); 
       } 
      } 
     } 
    } 

    private void initializeLocationManager() { 
     Log.e(TAG, "initializeLocationManager"); 
     if (mLocationManager == null) { 
      mLocationManager = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE); 
     } 
    } 
    public Cursor dis(String dis, double cos_lat_rad, double sin_lat_rad, double cos_lon_rad, double sin_lon_rad) { 

     Cursor cursor = db.rawQuery("SELECT barID ,(" + sin_lat_rad + "*\"SinLat\"+" + cos_lat_rad + "*\"CosLat\"*(" + sin_lon_rad + "*\"SinLong\"+" + cos_lon_rad + "*\"CosLong\")) AS \"distance_acos\" FROM BarDetails WHERE ("+sin_lat_rad+" * \"SinLat\" +"+ cos_lat_rad +"* \"CosLat\" * (+"+sin_lon_rad +"* \"SinLong\" + "+cos_lon_rad +"* \"CosLong\")) >"+dis+ " ORDER BY \"distance_acos\" DESC ", null); 
     return cursor; 

    } 

    public static double deg2rad(double deg) { 
     return (deg * Math.PI/180.0); 
    } 
} 

und ich rufe diesen Dienst wie dies in meinem Haupttätigkeit:

Intent intent = new Intent(MainActivity.this , service.class); 
     startService(intent); 

In meinem Manifest-Datei i folgendes enthalten sind:

<service android:name=".service" android:process=":my_service" /> 

hier ist mein logcat

04-22 21:11:00.960 18698-18698/com.example.android.find:my_service E/AndroidRuntime: FATAL EXCEPTION: main 
                        Process: com.example.android.find:my_service, PID: 18698 
                        java.lang.RuntimeException: Unable to instantiate service com.example.android.findbar.service: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference 
                         at android.app.ActivityThread.handleCreateService(ActivityThread.java:2962) 
                         at android.app.ActivityThread.access$1800(ActivityThread.java:178) 
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1553) 
                         at android.os.Handler.dispatchMessage(Handler.java:111) 
                         at android.os.Looper.loop(Looper.java:194) 
                         at android.app.ActivityThread.main(ActivityThread.java:5631) 
                         at java.lang.reflect.Method.invoke(Native Method) 
                         at java.lang.reflect.Method.invoke(Method.java:372) 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959) 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754) 
                        Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference 
                         at android.content.ContextWrapper.getResources(ContextWrapper.java:86) 
                         at android.widget.Toast.<init>(Toast.java:106) 
                         at android.widget.Toast.makeText(Toast.java:263) 
                         at com.example.android.findbar.service.makeToast(service.java:71) 
                         at com.example.android.findbar.service.access$000(service.java:19) 
                         at com.example.android.findbar.service$LocationListener.<init>(service.java:37) 
                         at com.example.android.findbar.service.<init>(service.java:90) 
                         at java.lang.reflect.Constructor.newInstance(Native Method) 
                         at java.lang.Class.newInstance(Class.java:1606) 
                         at android.app.ActivityThread.handleCreateService(ActivityThread.java:2959) 
                         at android.app.ActivityThread.access$1800(ActivityThread.java:178)  
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1553)  
                         at android.os.Handler.dispatchMessage(Handler.java:111)  
                         at android.os.Looper.loop(Looper.java:194)  
                         at android.app.ActivityThread.main(ActivityThread.java:5631)  
                         at java.lang.reflect.Method.invoke(Native Method)  
                         at java.lang.reflect.Method.invoke(Method.java:372)  
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)  
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)  

Answer 1

Schritt # 1: makeToast() loswerden.

Schritt 2: Warten Sie, bis die Felder Ihres Dienstes (z. B. mLocationListeners) initialisiert sind, bis onCreate() für den Dienst aufgerufen wird.

So wie es aussieht, versuchen Sie, einen Toast von einem Feldinitialisierer anzuzeigen, und das wird nicht funktionieren, da Service noch nicht eingerichtet ist.