code: public void shutdown() {
          final int taskCount = runningTasks.size();
          for (int i = 0; i < taskCount; ++i) {
              int key = runningTasks.keyAt(i);
              LoadBitmapTask t = runningTasks.get(key);
              t.cancel(true);
          }
          runningTasks.clear();
      }
docs: Stop all running loading tasks. This method should be called when your activity gets
  stopped (in {#onStop})