Implementing downloading data from internet using RXJAVA?

Question

Android

Good afternoon. I am trying to learn how to use RXjava in android but have run into a question. I load any data from the Internet, for example, links to images in a separate Schedulers.io thread pool and get bitmaps there, which I will later have to display in the grid view, my custom adapter was also written. But I don’t understand how I can transfer data from the io stream to the main stream, so that in the future these bitmap (pictures) will be attached to the ImageView. I read in articles on Habré that there are such methods as ObserveOn (Scheduler sch) and SubscribeOn, but I don’t fully understand how I can transfer data between streams using these methods to bind a bitmap to an ImageView. And another question, you can suggest books or some other articles in Russian, or code examples for RxJava2.