RxJavaSubscription.java

public class SubscriptionActivity extends Activity {
  
  Subscription subscription;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      
      subscription = getObservable()
              .subscribeOn(Schedulers.io())
              .observeOn(AndroidSchedulers.mainThread())
              .subscribe(getDummyObserver());
  }

  @Override
  protected void onDestroy() {
      super.onDestroy();
          // unsubscribe it when activity onDestroy is called
          subscription.unsubscribe();
  }

  public Observable<String> getObservable() {
      return RxAndroidNetworking.download(URL, dirPath, fileName)
              .build()
              .getDownloadObservable();
  }
}