media-samples | Multiple samples showing the best practices | Android library

I am new to Android (but not to java) and I am confused with Services, ViewModel, Broadcast things and other alternatives used to communicate between Activities. My communication needs are extremely basic.

Consider Midiscope's MainActivity. I want to do something like that, but with the Spinner to select the source on a different Activity. Basically one Activity for the Spinner (call it "SettingsActivity" but obviously cannot be a true Settings for reasons too long for this margin) and another Activity for the UI with the TextView, call it TextViewActivity. I am somewhat able to make it work if I share static variables to access the TextViewActivity from the Settings, so that I can create LoggingReceiver from the Settings but binding it to the TextViewActivity instead of Settings (this). Obviously this is not right (TM), so I attempted all the options I could google to no avail. What it the simplest way to accomplish this?

• I tried ViewModel and the example in the documentation crashes at MyViewModel model = new ViewModelProvider(this).get(MyViewModel.class);  with error: no suitable constructor found for ViewModelProvider(MyActivity) (yes, I voted 1 star on that documentation page). The "solution" from the accepted answer to a question about it (i.e. using new ViewModelProvider.NewInstanceFactory()) crashes with java.lang.RuntimeException: Cannot create an instance of class com.example.MyViewModel

• Then I tried IntentService as described at https://developer.android.com/guide/components/services but two things are unclear to me, so perhaps that's not the right approach for my problem:

  1. What should I do in onHandleIntent? My Intent does nothing per se, it should be only a pass-through between whatever comes from MIDI to my UI
  2. How can I access and use the IntentService from both the two Activities described above? Sure, the singleton pattern, but how to make sure I don't create the same problems that sharing a static instance of the Activity causes?