Creating new async tasks

Question

In the past, I have used AsyncTasks to perform network requests for my Android app. I recently switched to RxJava to be able to cancel the requests when the user exits an activity. I have created a system to easily create new async tasks via RxJava which all cancel when a user exits an activity. I have attached some basic code that I hope somebody could give me some pointers on.

public class BaseActivity extends AppCompatActivity{
 ArrayList<OnDestroyListener> listeners = new ArrayList<>();
 @Override
 protected void onDestroy() {
 for(OnDestroyListener listener : listeners){
 listener.onDestroy();
 }
 super.onDestroy();
 }
 public void addOnDestroyListener(OnDestroyListener listener){
 listeners.add(listener);
 }
 public interface OnDestroyListener{
 void onDestroy();
 }
}
public class Tools{
 public static <E> void observe(Callable<E> callable, SingleSubscriber<E> subscriber, BaseActivity activity){
 final Subscription sub = Single.fromCallable(callable)
 .subscribeOn(Schedulers.io())
 .observeOn(AndroidSchedulers.mainThread())
 .subscribe(subscriber);
 if(activity == null){
 return;
 }
 activity.addOnDestroyListener(new BaseActivity.OnDestroyListener() {
 @Override
 public void onDestroy() {
 sub.unsubscribe();
 }
 });
 }
}
public class Endpoint{
 public void makeGetRequestAsync(final String url, final SingleSubscriber<String> subscriber, BaseActivity activity){
 Tools.observe(new Callable<String>() {
 @Override
 public String call() throws Exception {
 return makeGetRequestSync(url);
 }
 }, subscriber, activity);
 }
}
public class SampleActivity extends BaseActivity{
 Endpoint endpoint = new Endpoint();
 void onButtonClick(View v){ 
 endpoint.makeGetRequestAsync("https://someurl.com", new SingleSubscriber<String>() {
 @Override
 public void onSuccess(String result) {
 //Request success
 }
 @Override
 public void onError(Throwable error) {
 //Request failure
 }
 }, this);
 }
}

I know that I do not have a real coding problem, since this method has been working very well so far, but I just want to know if anything about this process is inherently wrong, as I am using it throughout my app.

Answer 1

I would start by trying to make a separate package for making the requests, something like a presenter(MVP pattern - MVP in Android).
Because, the way you have it now, it is hard to be tested and inside of the activity you have more logic, breaking a bit the SRP principle( SRP ).

Now, all it is left to do is to connect the activity and the presenter and that you can do using a callback.
Also, as a bonus, all the stuff you need, presenter, etc, you can add to a dagger module.