void startAsyncThumbnailsLoading(ArrayList<POI> pois){
  if (pois == null)   return;
  mThreadPool.shutdownNow();
  mThreadPool=Executors.newFixedThreadPool(3);
  for (int i=0; i < pois.size(); i++) {
    final POI poi=pois.get(i);
    final Marker marker=mPoiMarkers.getItem(i);
    mThreadPool.submit(new ThumbnailLoaderTask(poi,marker));
  }
}

void startAsyncThumbnailsLoading ( ArrayList < POI > pois ) { if ( pois == null ) return ; mThreadPool . shutdownNow ( ) ; mThreadPool = Executors . newFixedThreadPool ( 3 ) ; for ( int i = 0 ; i < pois . size ( ) ; i ++ ) { final POI poi = pois . get ( i ) ; final Marker marker = mPoiMarkers . getItem ( i ) ; mThreadPool . submit ( new ThumbnailLoaderTask ( poi , marker ) ) ; } }
loads all thumbnails in background
