Correct way to communicate the result of a background thread to the Ui Thread in Android

This is one of the most confusing topics for me. So my question is, what is the correct way of communicate the result of background thread when this finish?.

Imagine I want to update some TextView with some information I just downloaded.There is 3 things I use when I need to perform background tasks:

AsyncTask

Very easy to use, this one has the onPostExecute() method that will return the result directly to the UiThread so I can use a callback interface or do whatever I want. I liked this class but it's deprecated.

ThreadPoolExecutor

This is what I actually use when need to perform background tasks and here comes my problem, the moment when I have to give the result to the UiThread. I have informed myself about Looper and Handler classes and about the mainLooper.

So, when I need to return some results I use the method runOnUiThread() that, as I have readed, just get the Looper of the Ui thread and post my Runnable to the queue.

Well this is working and I can communicate with the main thread but, I find it really ugly, and I am sure there is a more elegant way of doing it than populate all my code of "runOnUiThread()" methods. Also, if the background task need too much time, maybe the user already change of Activity or Fragment when the code inside runOnUiThread() runs what will cause Exceptions (I know using LiveData and MVVM pattern would solve this last problem but I am working in a legacy project and I can't refactor all the code so I am working with the clasical Activity mvc pattern)

So, there is another way of doing this? Could you give an example? I really searched a lot but didn't find anything...

Coroutines

I am actually working in a legacy project and I must use Java so can't use Kotlin coroutines, but I find them easy to use and so powerfull.

Any help would be appreciated!

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