getlastknownlocation() return null und App wird heruntergefahren

Question

ich versuche, den aktuellen Standort auf jeder einzelnen Sekunde zu erhalten, und ich tun dies mit AlarmManager und LocationListener und Location Manager. vor dem Einstellen des Alarms muss ich den aktuellen Standort für die Berechnung der allgemeinen Entfernung abrufen. wenn ich meine App auf AVD laufen und Lat & Long manuell mit DDMS die App funktioniert gut und macht den Job. Das Problem ist, wenn die App auf einem echten Gerät läuft, wird die App sofort heruntergefahren (es schlägt auch fehl, wenn ich die Position nicht manuell setze). was kann das problem bitte sein? Ich brauche nur aktuellen Standort zu erhalten, wenn eine Schaltfläche geklickt wird und jeweils einige Sekunden ...

GPSTracker.Java:

public class GPSTracker extends Service implements LocationListener { 

private final Context mContext; 

// flag for GPS status 
boolean isGPSEnabled = false; 

// flag for network status 
boolean isNetworkEnabled = false; 

// flag for GPS status 
boolean canGetLocation = false; 

Location location; // location 
double latitude; // latitude 
double longitude; // longitude 

// The minimum distance to change Updates in meters 
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters 

// The minimum time between updates in milliseconds 
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute 

// Declaring a Location Manager 
protected LocationManager locationManager; 


public GPSTracker(Context context) { 
    this.mContext = context; 
    getLocation(); 
} 


public Location getLocation() { 
    try { 
     locationManager = (LocationManager) mContext 
       .getSystemService(LOCATION_SERVICE); 

     // getting GPS status 
     isGPSEnabled = locationManager 
       .isProviderEnabled(LocationManager.GPS_PROVIDER); 

     // getting network status 
     isNetworkEnabled = locationManager 
       .isProviderEnabled(LocationManager.NETWORK_PROVIDER); 

     if (!isGPSEnabled && !isNetworkEnabled) { 
      // no network provider is enabled 
     } else { 
      this.canGetLocation = true; 
      // First get location from Network Provider 
      if (isNetworkEnabled) { 
       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 location; 
       } 
       locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
       Log.d("Network", "Network"); 
       if (locationManager != null) { 
        location = 
        locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 
        if (location != null) { 
         latitude = location.getLatitude(); 
         longitude = location.getLongitude(); 
        } 
       } 
      } 
      // if GPS Enabled get lat/long using GPS Services 
      if (isGPSEnabled) { 
       if (location == null) { 
        locationManager.requestLocationUpdates(
          LocationManager.GPS_PROVIDER, 
          MIN_TIME_BW_UPDATES, 
          MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
        Log.d("GPS Enabled", "GPS Enabled"); 
        if (locationManager != null) { 
         location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 
         if (location != null) { 
          latitude = location.getLatitude(); 
          longitude = location.getLongitude(); 
         } 
        } 
       } 
      } 
     } 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 

    return location; 
} 

/** 
* Stop using GPS listener 
* Calling this function will stop using GPS in your app 
* */ 
public void stopUsingGPS() { 
    if (locationManager != null) { 
     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; 
     } 
     locationManager.removeUpdates(GPSTracker.this); 
     Log.d("GPS is stopped", "GPS is stopped"); 
    } 
} 

/** 
* Function to get latitude 
* */ 
public double getLatitude() { 
    if (location != null) { 
     latitude = location.getLatitude(); 
    } 

    // return latitude 
    return latitude; 
} 

/** 
* Function to get longitude 
* */ 
public double getLongitude() { 
    if (location != null) { 
     longitude = location.getLongitude(); 
    } 

    // return longitude 
    return longitude; 
} 

/** 
* Function to check GPS/wifi enabled 
* @return boolean 
* */ 
public boolean canGetLocation() { 
    return this.canGetLocation; 
} 

/** 
* Function to show settings alert dialog 
* On pressing Settings button will lauch Settings Options 
* */ 
public void showSettingsAlert() { 
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext); 

    // Setting Dialog Title 
    alertDialog.setTitle("GPS is settings"); 

    // Setting Dialog Message 
    alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?"); 

    // On pressing Settings button 
    alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() { 
     public void onClick(DialogInterface dialog, int which) { 
      Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
      mContext.startActivity(intent); 
     } 
    }); 

    // on pressing cancel button 
    alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
     public void onClick(DialogInterface dialog, int which) { 
      dialog.cancel(); 
     } 
    }); 

    // Showing Alert Message 
    alertDialog.show(); 
} 




@Override 
public void onLocationChanged(Location location) { 
} 

@Override 
public void onProviderDisabled(String provider) { 
} 

@Override 
public void onProviderEnabled(String provider) { 
} 

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

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

Alarm.Java:

@Override 
public void onReceive(Context context, Intent intent) { 

    /** PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE); 
    PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, ""); 
    wl.acquire();**/ 

    // Put here YOUR code. 
    //Intent i= new Intent(this,AlarmActivity.class); 
    //startActivity(i); 

    try { 


     gps = new GPSTracker(context); 
     double latitude = gps.getLatitude(); 
     double longitude = gps.getLongitude(); 

     Location CurrLoc = gps.getLocation(); 
     Location DistLoc = new Location("wow"); 
     DistLoc.setLatitude(32.159141); 
     DistLoc.setLongitude(34.922564); 
     float CurrDistance = CurrLoc.distanceTo(DistLoc); 

     SharedPreferences prefs = context.getSharedPreferences("AlarmDistanceAndUserStatus", Context.MODE_PRIVATE); 
     float AlarmDistance=prefs.getFloat("AlarmDistance",0); 


     Log.d("distance invoke alarmRe",String.valueOf(AlarmDistance)); 
     Log.d("current distance is:",String.valueOf(CurrDistance)); 

     // Log.d("Run once -2",String.valueOf(AlarmActivity.RUN_ONCE)); 
     // Log.d("distance invoke alarm-2",String.valueOf(AlarmActivity.AlarmDistance)); 
     if(CurrDistance>=0 && CurrDistance<=50){ 
      SharedPreferences.Editor editor=prefs.edit(); 
      editor.putBoolean("UserStatus",false); 
      editor.commit(); 
      this.CancelAlarm(context); 

      Bundle bundle = intent.getExtras(); 
      String message = bundle.getString("alarm_message"); 

      Intent newIntent = new Intent(context, AlarmActivity.class); 
      newIntent.putExtra("alarm_message", message); 
      newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
      context.startActivity(newIntent); 
     } 
     else if(AlarmDistance>=CurrDistance){ 
      Bundle bundle = intent.getExtras(); 
      String message = bundle.getString("alarm_message"); 

      Intent newIntent = new Intent(context, AlarmActivity.class); 
      newIntent.putExtra("alarm_message", message); 
      newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
      context.startActivity(newIntent); 
     } 


     Toast.makeText(context, "Your Location is - \nLat: " + latitude + "\nLong: " + longitude + " distanceto:" + CurrDistance + " from AlaramSet!!!", Toast.LENGTH_LONG).show(); 

     Log.d("onReceive", "onReceive"); 

    } catch (Exception e) { 
     Toast.makeText(context, "There was an error somewhere, but we still received an alarm", Toast.LENGTH_SHORT).show(); 
     e.printStackTrace(); 

    } 

    // Toast.makeText(context, "Alarm !!!!!!!!!!", Toast.LENGTH_LONG).show(); // For example 

    //wl.release(); 
} 


public void SetAlarm(Context context,int SecondsInterval) { 

    Calendar calendar = Calendar.getInstance(); 
    calendar.add(Calendar.SECOND, SecondsInterval); 
    AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE); 
    Intent i = new Intent(context, Alarm.class); 
    PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0); 
    am.setInexactRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), (1000 * SecondsInterval), pi); // Millisec * Second * Minute 
    Toast.makeText(context, "Alarm Set!!!", Toast.LENGTH_LONG).show(); 

} 

public void CancelAlarm(Context context) { 

    Intent intent = new Intent(context, Alarm.class); 
    PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0); 
    AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE); 
    alarmManager.cancel(sender); 
    Toast.makeText(context, "Alarm Canceled!!!", Toast.LENGTH_LONG).show(); 
} 

AlarmActivity.Java:

Öffentliche Klasse AlarmActivity erweitert AppCompatActivity { public static boolean RUN_ONCE = true;

GPSTracker gps; 
Alarm alarm; 
SharedPreferences sharedpref; 
boolean UserStatus=true; 

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

    alarm = new Alarm(); 
    Log.d("Run once -2", String.valueOf(RUN_ONCE)); 
    runOnce(); 
    sharedpref=getSharedPreferences("AlarmDistanceAndUserStatus", Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor=sharedpref.edit(); 
    UserStatus=sharedpref.getBoolean("UserStatus",true); 
    Log.d("UserStatus now is:", String.valueOf(UserStatus)); 
    if(UserStatus){ 
     Button OkStopButton=(Button)findViewById(R.id.OkStopButton); 
     OkStopButton.setVisibility(View.VISIBLE); 
     TextView WakeUpTimeTextView=(TextView)findViewById(R.id.WakeUpTimeTextView); 
     WakeUpTimeTextView.setVisibility(View.VISIBLE); 

     Button DidItButton=(Button)findViewById(R.id.DidItButton); 
     Button MissItButton=(Button)findViewById(R.id.MissItButton); 
     DidItButton.setVisibility(View.INVISIBLE); 
     MissItButton.setVisibility(View.INVISIBLE); 
     TextView DestArrivedTextView=(TextView)findViewById(R.id.DestArrivedTextView); 
     DestArrivedTextView.setVisibility(View.INVISIBLE); 
    } 
    else{ 
     Button OkStopButton=(Button)findViewById(R.id.OkStopButton); 
     OkStopButton.setVisibility(View.INVISIBLE); 
     TextView WakeUpTimeTextView=(TextView)findViewById(R.id.WakeUpTimeTextView); 
     WakeUpTimeTextView.setVisibility(View.INVISIBLE); 

     Button DidItButton=(Button)findViewById(R.id.DidItButton); 
     Button MissItButton=(Button)findViewById(R.id.MissItButton); 
     DidItButton.setVisibility(View.VISIBLE); 
     MissItButton.setVisibility(View.VISIBLE); 
     TextView DestArrivedTextView=(TextView)findViewById(R.id.DestArrivedTextView); 
     DestArrivedTextView.setVisibility(View.VISIBLE); 

    } 
} 

private void runOnce() { 
    if (RUN_ONCE) { 
     RUN_ONCE = false; 
     gps = new GPSTracker(AlarmActivity.this); 
     if (gps.canGetLocation) { 

      double latitude = gps.getLatitude(); 
      double longitude = gps.getLongitude(); 
      Location loc = gps.getLocation(); 
      Location dist = new Location("wow"); 
      dist.setLatitude(32.159058); 
      dist.setLongitude(34.922536); 
      float FirstDistance = loc.distanceTo(dist); 
      Log.d("first distance",String.valueOf(FirstDistance)); 

      //System.currentTimeMillis() 
      //interval time of distance check 
      int SecondsInterval; 
      if (FirstDistance >= 0 && FirstDistance <= 1000) SecondsInterval = 3; 
      else if (FirstDistance > 1000 && FirstDistance <= 2000) SecondsInterval = 4; 
      else if (FirstDistance > 2000 && FirstDistance <= 3500) SecondsInterval = 5; 
      else SecondsInterval = 8; 
      /// 
      //check the distance to alarm user before dist. station 
      int MissingCount = 2;//for example-import from db 

      float AlarmDistance= (FirstDistance/ 10) * MissingCount; 
      sharedpref=getSharedPreferences("AlarmDistanceAndUserStatus",Context.MODE_PRIVATE); 
      SharedPreferences.Editor editor=sharedpref.edit(); 
      editor.putFloat("AlarmDistance",AlarmDistance); 
      editor.putBoolean("UserStatus",true); 
      editor.commit(); 


      alarm.SetAlarm(this,SecondsInterval); 
      Intent newIntent = new Intent(this, MainActivity.class); 
      this.startActivity(newIntent); 
     } else { 
      gps.showSettingsAlert(); 
     } 


    } 
} 


public void StopOnClick(View v) { 

    // gps.stopUsingGPS(); 

    RUN_ONCE = true; 
    sharedpref=getSharedPreferences("AlarmDistanceAndUserStatus",Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor=sharedpref.edit(); 
    editor.putFloat("AlarmDistance",0); 
    editor.putBoolean("UserStatus",true); 
    editor.commit(); 
    alarm.CancelAlarm(this); 
    //back to Home Page 
} 

public void DidItOnClick(View v){ 
    //Return to Home Page (e.g: MainActivity) 
    Intent newIntent = new Intent(this, MainActivity.class); 
    this.startActivity(newIntent); 


    RUN_ONCE = true; 
    sharedpref=getSharedPreferences("AlarmDistanceAndUserStatus",Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor=sharedpref.edit(); 
    editor.putFloat("AlarmDistance",0); 
    editor.putBoolean("UserStatus", true); 
    editor.commit(); 
} 

public void MissItOnClick(View v){ 
    //go check altenative ways 


    RUN_ONCE = true; 
    sharedpref=getSharedPreferences("AlarmDistanceAndUserStatus",Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor=sharedpref.edit(); 
    editor.putFloat("AlarmDistance",0); 
    editor.putBoolean("UserStatus",true); 
    editor.commit(); 
} 

}

das Scheitern:

Unable to start activity ComponentInfo{com.example.liorozit.gpstest/com.example.liorozit.gpstest.AlarmActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'float android.location.Location.distanceTo(android.location.Location)' on a null object reference 

gibt es eine externe Klasse, die von Intent AlarmActivity Klasse bewegen, und rufen Sie es OnCraete(). Was kann ich tun, um das Problem zu beheben und meinen aktuellen Standort zu bekommen? Danke!

Answer 1

Wenn Sie den Standort in Ihrer Aktivität abrufen möchten und nicht im Hintergrund ausgeführt werden müssen, können Sie dies versuchen.

package com.jmarkstar.activitylocation; 

import android.content.Context; 
import android.location.Criteria; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.widget.Toast; 

public class MainActivity extends AppCompatActivity { 

    private LocationManager locationManager; 
    private MyLocationListener locationListener; 
    private String latitude; 
    private String longitude; 

    @Override 
    protected void onStart() { 
     super.onStart(); 

     locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE); 
     locationListener = new MyLocationListener(); 
     Criteria criteria = new Criteria(); 
     criteria.setAltitudeRequired(false); 
     criteria.setBearingRequired(false); 
     criteria.setCostAllowed(false); 
     criteria.setPowerRequirement(Criteria.ACCURACY_FINE); 

     String bestEnabledProvider = locationManager.getBestProvider(criteria, true); 
     locationManager.requestLocationUpdates(bestEnabledProvider, 0, 0, locationListener); 
    } 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     //YOU CODE 
    } 

    private class MyLocationListener implements LocationListener { 

      @Override 
      public void onLocationChanged(Location location) { 
       makeUseOfNewLocation(location); 
       locationManager.removeUpdates(locationListener); 
      } 

      private void makeUseOfNewLocation(final Location location) { 
       if (location != null) { 
        String message = "position: " + location.getLatitude() + ", " + location.getLongitude() + " accuracy: " + location.getAccuracy(); 
        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show(); 

        latitude = String.valueOf(location.getLatitude()); 
        longitude = String.valueOf(location.getLongitude()); 

        //YOUR CODE 
       } 
      } 

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

     @Override 
     public void onProviderEnabled(String provider) {} 

     @Override 
     public void onProviderDisabled(String provider) {} 
    } 
}