Cant Run Background Service
I am trying to use LocationListener class in a background service to receive the current location of user every time and then comparing it with some data stored in my database. but
Solution 1:
The LogCat states:
Caused by: java.lang.NullPointerException
at android.content.ContextWrapper.getSystemService(ContextWrapper.java:416)
at com.example.alert.service.<init>(service.java:15)
Simply wait for the Context to be initialized by moving this code into onCreate():
publicclassserviceextendsService {
LocationManager lm;
@OverridepublicvoidonCreate() {
// This line needs an existing context
lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Toast.makeText(this, "Background Service Created", Toast.LENGTH_LONG).show();
}
// etcSolution 2:
Make sure that you have added service to the AndroidManifest file
A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use. Each service class must have a corresponding declaration in its package's AndroidManifest.xml. Services can be started with Context.startService() and Context.bindService().
Solution 3:
Use this code my friend and make changes according to your need
publicclassMainActivityextendsActivity {
Button btnStart, btnStop;
publicstaticContext mContext;
Intent it;
publicLocationManager manager;
publicboolean isGPSEnabled = false;
boolean isNetworkEnabled = false;
@OverrideprotectedvoidonCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mContext = this;
manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
isGPSEnabled = manager.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = manager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
btnStart = (Button) findViewById(R.id.btnStart);
btnStop = (Button) findViewById(R.id.btnStop);
btnStart.setOnClickListener(newView.OnClickListener() {
@OverridepublicvoidonClick(View v) {
// TODO Auto-generated method stub/*if (isGPSEnabled) {
startService(getIntent());
}
else
{
Toast.makeText(MainActivity.this, "Please oN Gps ",
Toast.LENGTH_LONG).show();
}*/startService(getIntent());
}
});
btnStop.setOnClickListener(newView.OnClickListener() {
@OverridepublicvoidonClick(View v) {
// TODO Auto-generated method stubstopService(getIntent());
}
});
} // on create ends@OverridepublicbooleanonCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);
returntrue;
}
publicIntentgetIntent() {
it = newIntent(mContext, MyService.class);
return it;
} // method endspublicstaticContextgetContextForService() {
return mContext;
} // methods ends
} // final class endsHere is Your service for Location
publicclassMyServiceextendsService {
// flag for GPS statuspublicstatic LocationManager manager;
publicstaticbooleanisGPSEnabled=false;
publicstaticdoublelattitude=0;
publicstaticdoublelongitude=0;
intcount=0;
// flag for network statusbooleanisNetworkEnabled=false;
// flag for GPS statusbooleancanGetLocation=false;
MyFile myFile;
@Overridepublic IBinder onBind(Intent intent) {
// TODO Auto-generated method stubreturnnull;
} // method ends@OverridepublicintonStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);
System.out.println("On Start Command is called ");
return START_STICKY;
} // method ends@OverridepublicvoidonCreate() {
// TODO Auto-generated method stubsuper.onCreate();
System.out.println("Service is created//////////// ");
// start asyntask to get locationsnewGetLocations().execute();
}// on create ends@OverridepublicvoidonDestroy() {
// TODO Auto-generated method stubsuper.onDestroy();
System.out.println("Service is Destroyed //////////// ");
if (manager != null && isGPSEnabled == true) {
manager.removeUpdates(mylistener);
System.out.println("Service is Destroyed under if //////////// ");
}
} // method endspublicclassGetLocationsextendsAsyncTask<Void, Void, Void> {
@OverrideprotectedvoidonPreExecute() {
// TODO Auto-generated method stubsuper.onPreExecute();
manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = manager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = manager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (isGPSEnabled) {
/*
* Criteria criteria = new Criteria(); String bestProvider =
* manager.getBestProvider(criteria, false); Location location =
* manager.getLastKnownLocation(bestProvider); double lat
* =location.getLatitude(); double longi
* =location.getLongitude();
* System.out.println("getting location continous ////// Lattti "
* +location.getLatitude() );
* System.out.println("getting location continous ////// LONGITU "
* + location.getLongitude());
*/
manager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER, 3000, 0, mylistener);
} else {
Toast.makeText(MyService.this, "Please oN Gps ",
Toast.LENGTH_LONG).show();
}
}
@Overrideprotected Void doInBackground(Void... params) {
// TODO Auto-generated method stub// getting current lattitude and longitudereturnnull;
}// method ends
}// asyntask class endsvoidhandleLocationChanged(Location loc) {
lattitude = loc.getLatitude();
longitude = loc.getLongitude();
/*Toast.makeText(MyService.this,
"lat is " + lattitude + " long is " + longitude,
Toast.LENGTH_LONG).show();*/
System.out.println("getting location continous ////// Lattti "
+ lattitude);
System.out.println("getting location continous ////// LONGITU "
+ longitude);
generateNoteOnSD("GpsTesting.txt", "lattitude is" + lattitude + "\n"
+ " longitude" + longitude);
} // method endspublicLocationListenermylistener=newLocationListener() {
@OverridepublicvoidonLocationChanged(Location loc) {
handleLocationChanged(loc);
}
publicvoidonProviderDisabled(String arg0) {
// TODO Auto-generated method stub// Toast.makeText(mContext, "Gps is disable",// Toast.LENGTH_SHORT).show();
}
publicvoidonProviderEnabled(String arg0) {
// TODO Auto-generated method stub// Toast.makeText(mContext, "Gps is on", Toast.LENGTH_SHORT).show();
}
publicvoidonStatusChanged(String arg0, int arg1, Bundle arg2) {
// TODO Auto-generated method stub// Toast.makeText(appcontext, "Gps status is chnged ",// Toast.LENGTH_SHORT).show();
}
};
publicvoidshowSettingsAlert() {
AlertDialog.BuilderalertDialog=newAlertDialog.Builder(
MainActivity.getContextForService());
// Setting Dialog Title
alertDialog.setTitle("Alert");
// Setting Dialog Message
alertDialog
.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings",
newDialogInterface.OnClickListener() {
publicvoidonClick(DialogInterface dialog, int which) {
Intentintent=newIntent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
getApplicationContext().startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel",
newDialogInterface.OnClickListener() {
publicvoidonClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}// method ends// method for sending notiifcationpublicvoidsendNotification() {
intMY_NOTIFICATION_ID=1;
PendingIntentcontentIntent= PendingIntent.getActivity(
getApplicationContext(), 0, newIntent(MyService.this,
MainActivity.class), 0);
NotificationmyNotification=newNotificationCompat.Builder(
getApplicationContext())
.setContentTitle("Notification for Lat and Long")
.setContentText("hi testing notiifaction on lat and long")
.setTicker(" ToDoList Notification")
.setWhen(System.currentTimeMillis())
.setContentIntent(contentIntent)
.setDefaults(Notification.DEFAULT_SOUND).setAutoCancel(true)
.setSmallIcon(R.drawable.ic_launcher).build();
NotificationManagernotificationManager= (NotificationManager) MainActivity
.getContextForService().getSystemService(
Context.NOTIFICATION_SERVICE);
notificationManager.notify(MY_NOTIFICATION_ID, myNotification);
} // method ends// writing file onpublicvoidgenerateNoteOnSD(String sFileName, String sBody) {
try {
Fileroot=newFile(Environment.getExternalStorageDirectory()
+ "/sdcard", "Gps_Data");
if (!root.exists()) {
root.mkdirs();
}
Filegpxfile=newFile(root, sFileName);
FileWriterwriter=newFileWriter(gpxfile);
writer.append(sBody);
writer.flush();
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
} // method endsprivatebooleanhaveNetworkConnection() {
booleanhaveConnectedWifi=false;
booleanhaveConnectedMobile=false;
ConnectivityManagercm= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo[] netInfo = cm.getAllNetworkInfo();
for (NetworkInfo ni : netInfo) {
if (ni.getTypeName().equalsIgnoreCase("WIFI"))
if (ni.isConnected())
haveConnectedWifi = true;
if (ni.getTypeName().equalsIgnoreCase("MOBILE"))
if (ni.isConnected())
haveConnectedMobile = true;
}
return haveConnectedWifi || haveConnectedMobile;
}
} // final class ends
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