BLE works in background in Android

Question

I'm implementing an app that It makes the search for ble devices connected, giving me back the mac address of the device. I have already found everything here: Android listing BLE devices after device scan or https://developer.android.com/guide/topics/connectivity/bluetooth-le.html

, the problem is that I want him in the background when open the activity called "track.java". I want that when you open the track activity, in the background you open the scanning process BLE and, when detected, it displays in a popup window. This is "Track.java"

package com.example.giacomob.myapplication;

import android.content.ActivityNotFoundException;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;

/**
 * Created by Giacomo B on 07/08/2015.
 */
public class Track extends FragmentActivity implements LocationListener {

    private String providerId = LocationManager.GPS_PROVIDER;
    private LocationManager locationManager=null;
    private static final int MIN_DIST=20;
    private static final int MIN_PERIOD=30000;
    int maxrows=8;

    float distance = 0;
/*


    // Initializes Bluetooth adapter.
    final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();
*/

    GPSTracker gps;
    double  newLatitude;
    double newLongitude;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_track);
        this.locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

//////////////mi sa che questi non servno
    /*    double currentLat = 51.43376;
        double currentLng = -2.86221;
        double destLat = 51.43503;
        double destLng = -2.86869;

        Location here = new Location("Current");
        here.setLatitude(currentLat);
        here.setLongitude(currentLng);

        Location dest = new Location("Destination2");
        dest.setLatitude(destLat);
        dest.setLongitude(destLng);

        Log.d("GPS", "Bearing to dest: " + here.bearingTo(dest));
        Log.d("GPS", "Distance to dest: " + here.distanceTo(dest));
*/
        String dato1 = getIntent().getExtras().getString("Destination"); //preleva la stringa
        int position = getIntent().getExtras().getInt("Posizione");
        //int position = position1-(position1%maxrows)+1;
      //  if(position1%maxrows==0)
         //   position = position1-1;
        //else

        String paese = getIntent().getExtras().getString("Paese");
        System.out.println("La posizione è"+position);
    //    System.out.println("Il paese è"+paese);
        String[] arr = dato1.split("\\|");
        int countc = 0;
        int paesi = 0;


        for(int i =3; i<arr.length;i=i+maxrows){
            if(arr[i].equals(paese)){
                paesi++;
            }
        }


        String[] coord = new String[paesi*2];

        for(int i =3; i<arr.length;i=i+maxrows){
            if(arr[i].equals(paese)){
                coord[countc]= arr[i-3];
                countc++;
                coord[countc]= arr[i-2];
                countc++;

            }
        }

        //------------- da questo punto in poi implementerò il ciclo che mi dia le coordinate x e y esatte scelte dall'utente
        int x=0,y=0;
        boolean stop = false;

        for (int k=1,q=0; stop == false; k++,q=q+2 )
            if((position%((maxrows+2)*k) == 0) && (k==1)){ //+2 perchè rispetto al file dell xml abbiamo due righe inpiù, una per il pulsante ed una per la distanza
                x=q;
                y=q+1;
                stop = true;
            }
        else if ((position%(((maxrows+2)*k)+(k-1)) == 0) && (k!=1)){ //+2 perchè rispetto al file dell xml abbiamo due righe inpiù, una per il pulsante ed una per la distanza
                x=q;
                y=q+1;
                stop = true;
            }

        System.out.println("x vale "+x+" y vale "+y);

        //---------- fine ciclo

  /*

        for(int i =0; i<arr.length;i++) {
            System.out.println("Questa è la stringa coord" + coord[i]);
        }

    */
        /*String[] coordinate;//////////////////////////////////////////////////////////////////////voglio fare in modo che mi passi solo le coordinate col paese
        for(int k=0; k<arr.length; k++)
            for(int j=0+k; j<c*8+3; j++){
                if(arr[k]==paese) {
                    coordinate[j] = arr[k-2]
                }
            }
        */

        //map.setMyLocationEnabled(true);
        // centra la mappa su CENTER_POINT, con zoom 5

        try
        {
            // find actual position
            gps = new GPSTracker(Track.this);

                if (gps.canGetLocation()) {
                    newLatitude = gps.getLatitude();
                    newLongitude = gps.getLongitude();
                    // check if GPS enabled
       /*     while(newLatitude ==0 && newLongitude ==0) { //While aggiunto da me
               // Toast.makeText(getBaseContext(), "Attendi", Toast.LENGTH_SHORT).show();
            }*/     if(newLatitude != 0 && newLongitude !=0) {
                        for (int delay = 0; delay < 5; delay++) { //moltiplico per 5 la durata del toast
                            Toast.makeText(getBaseContext(), "lat : " + newLatitude + "long : " + newLongitude + "/n Per cambiare modalita' percorso (mezzo/piedi) clicca sulla destinazione", Toast.LENGTH_SHORT).show();
                        }
                    }
                    //////////////////////
                    final LatLng CENTER_POINT=new LatLng(newLatitude, newLongitude);
                    GoogleMap map=((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
                    map.setMyLocationEnabled(true);
                    map.moveCamera(CameraUpdateFactory.newLatLngZoom(CENTER_POINT, 5));
                    /////////////////////

                    //++++++++++++++++++++++++
                    if(newLatitude == 0 && newLongitude ==0) {
                        Toast.makeText(getBaseContext(), "GPS non disponibile, necessario attivare la rete dati.", Toast.LENGTH_SHORT).show();
                       // NavUtils.navigateUpTo(this,
                         //       new Intent(this, Page1.class));

                      //  Intent openPage1 = new Intent(Track.this, Page1.class);
                      //  startActivity(openPage1);
                    }
                    else {///////////////////////////////////////////// è qui che al posto di arr[0] e arr[1], metterò il numero corrispondente alla riga scelta+posizione delle coordinate*8
                        String uri = String.format("http://maps.google.com/maps?f=d&saddr=%1$s,%2$s&daddr=%3$s,%4$s &hl=en", newLatitude, newLongitude, coord[x], coord[y]);

                   //     String uri = String.format("http://maps.google.com/maps?f=d&saddr=%1$s,%2$s&daddr=%3$s,%4$s &hl=en", newLatitude, newLongitude, coord[0], coord[1]);
                        //http://maps.google.com/maps?f=d&saddr=Cannole&daddr=Lecce WA&hl=en
                        Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse(uri));
                        i.setComponent(new ComponentName("com.google.android.apps.maps", "com.google.android.maps.MapsActivity"));
                        startActivity(i);
                        Intent searchBLE = new Intent(Track.this, LogService.class);
                        startActivity(searchBLE);
                    }
                    //++++++++++++++++++++++++


                } else {
                    // can't get location
                    // GPS or Network is not enabled
                    // Ask user to enable GPS/network in settings
                    gps.showSettingsAlert();
                }

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


    }
    @Override
        protected void onResume() {
            System.out.println("On Resume");
        /*
        if (!locationManager.isProviderEnabled(providerId))
        {
            Intent gpsOptionsIntent = new Intent(
                    android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            startActivity(gpsOptionsIntent);
        }*/
        super.onResume();
         locationManager  = (LocationManager) getSystemService(LOCATION_SERVICE);
        if (!locationManager.isProviderEnabled(providerId))
        {
            System.out.println("is Provider Enabled");
            Intent gpsOptionsIntent = new Intent(
                    android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            startActivity(gpsOptionsIntent);
        }
        else {
            System.out.println("no Provider Enabled");
            locationManager.requestLocationUpdates(providerId, MIN_PERIOD, MIN_DIST, this);
        }
      /*  new CountDownTimer(5000, 1000) { // 5000 = 5 sec

            public void onTick(long millisUntilFinished) {

            }

            public void onFinish() {
                Intent searchBLE = new Intent(Track.this, LogService.class);

                startActivity(searchBLE);
            }
        }.start();
*/

}



    private void updateGUI(Location location)
    {
        System.out.println("updateGUI");
        double latitude=location.getLatitude();
        double longitude=location.getLongitude();
        String msg="Ci troviamo in coordinate ("+latitude+","+longitude+")";
        TextView txt= (TextView) findViewById(R.id.locationText);
        System.out.println(msg);
        txt.setText(msg);
    }

    @Override
    protected void onPause()
    {
        System.out.println("On Pause");
        super.onPause();
        locationManager.removeUpdates(this);
    }
    @Override
    public void onLocationChanged(Location location)
    {
        System.out.println("On location changed");
        updateGUI(location);
    }


    @Override
    public void onStatusChanged(String s, int i, Bundle bundle)
    { }

    @Override
    public void onProviderEnabled(String s)
    { }

    @Override
    public void onProviderDisabled(String s)
    {  }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }



}

can someone help me? Thanks, I'm desperate