Execute location listener while switch button is active

I have a simple app containing a switch button (on/off) and a code which shows the current gps coordinates. I can't seems to combine those two. I want the locationmanager/listener will only operate while the switch is on 'on' mode. Any ideas ?

Thank you. here is the code :

public class GpsPage extends ActionBarActivity {

TextView tz;
TextView textLat;
TextView textLong;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_gps_page);

    tz = (TextView) findViewById(R.id.textviewtz);
    Intent intent = getIntent();
    String TeudatZeut = intent.getStringExtra("tz");
    tz.setText("תעודת זהות " + TeudatZeut);

    Switch onOffSwitch = (Switch) findViewById(R.id.switch1);
    onOffSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            Toast.makeText(getApplicationContext(), "It's on", Toast.LENGTH_SHORT).show();
        }
    });

    textLat = (TextView) findViewById(R.id.textLat);
    textLong = (TextView) findViewById(R.id.textLong);

    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    LocationListener ll = new myLocationListener();
    lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, ll);
}
    class myLocationListener implements LocationListener {

        @Override
        public void onLocationChanged(Location location) {
            if (location != null) {
                double pLong = location.getLongitude();
                double pLat = location.getLatitude();
                double pAlt = location.getAltitude();
                double pAcc = location.getAccuracy();
                double pTime = location.getTime();
                double pSpeed = location.getSpeed();
                double pHeading =location.getBearing();
                textLat.setText(Double.toString(pLat));
                textLong.setText(Double.toString(pLong));
            }

        }

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

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {

        }
    }








@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_gps_page, 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);
}

}