GetArtistEventsEventBus.kt

// Somewhere on the UI thread
class MyActivity : Activity {
  val eventBus: EventBus
  //...
  
  fun getData() {
    showProgress()
    eventBus.post(FetchArtistEventsEvent(artist))
  }
    
  @Subscribe(threadMode=ThreadMode.MAIN)
  fun onEvent(event: RetrieveArtistEventsEvent){
    hideProgress()
    showEvents(event.artistEvents) 
  }
  
}


class ArtistRepository {
  val eventBus: EventBus
  //...
  
  @Subscribe(threadMode=ThreadMode.BACKGROUND)
  fun onEvent(event: FetchArtistEventsEvent) {
    // Check if data has been stored over an hour ago from now
    if (RepositoryUtil.isCacheStale(sharedPreferences, "ArtistEvent", event.artist.name, TimeUnit.HOURS.toSeconds(1))) {
        // Reset the cache time to "now"
        RepositoryUtil.resetCache(sharedPreferences, "ArtistEvent", event.artist.name)
        // Call webservice synchronously
        val freshEvents =  api.findArtistEvents(event.artist.name).execute().body()
        // Update/Insert events in database 
        bandsInTownDatabase.artistEventDao().upsert(freshEvents)
    }
    eventBus.post(RetrieveArtistEventsEvent(database.artistEventDao().getEventsByArtistId(event.artist.id)))
  }
  
  
  class FetchArtistEventsEvent(val artist: Artist)
  class RetrieveArtistEventsEvent(val artistEvents: List<ArtistEvent>?)
}

// Retrofit web service interface
interface BandsInTownApi {
    @GET("/artists/{artistName}/events")
    fun findArtistEvents(
        @Path("artistName") artistName: String
    ): Call<List<ArtistEventResponse>>
}