So, What’s the Point of This?

On the surface, this all seems fairly silly. One could just as easily override the lifecycle methods on MainActivity and log directly to the RecyclerView, bypassing all this Lifecycle and LifecycleObserver stuff.

The reason why Lifecycle and LifecycleObserver exist is to provide a standardized way of having other classes find out about lifecycle changes. Overriding the lifecycle methods on an activity or fragment tell that activity or fragment about the changes, but that’s it.

So, for example, LiveData — the subject of the next chapter — is a LifecycleObserver, so it knows about lifecycle events and can activate/deactivate accordingly. Other libraries may implement LifecycleObserver so they can be plugged into your activities and fragments and find out about lifecycle events, without you having to manually dispatch those events to them.

In ordinary apps, though, most developers will not be creating their own LifecycleObserver classes, though anyone can, as the sample app demonstrates. The focus for most app developers using the Architecture Components will be on LiveData and, later, ViewModel.