HostPinger - Exploring MVVM vs MVP using Google's Lifetime Aware components

Introduction

I was looking to explore best how to implement a fairly simple task of showing a list of Websites, and getting the latency of connecting to them. This lead me to explore how the MVVM and MVP frameworks might look when using Google's new Lifecycle Aware Components.

MVVM

MVVM sits well the the ViewModel class provided and is Lifecycle aware. The ViewModel is not recreated on rotation. LiveData is used to decouple the ViewModel and the View (Activity).

MVP

MVP normally has a interface or contract between the View and the Presenter. With lambdas in Kotlin, you can inject code into the Presenter and so in my case I did not require
MVP requires more work (and is still incomplete). It is not yet Lifecycle aware.

Approach

I have used the new lifecycle aware ViewModel to remove domain logic from the UI. This will help make the testing without involving the UI easier.
Retrofit and RXJava2 make good partners for dealing with the Async tasks
Latency code was adapted from a sample on Stack overflow
Latency results are cached to prevent re-testing on rotation.
Latency is only tested when the host is loaded by the RecyclerView. This can be seen by scrolling down on a slow connection. It prevent a very long list from being tested all at once, but limiting you to what you can see on the screen. (This may change when I change how the threading of the tests are run) Kotlin experimental coroutines are used for making the latency test non blocking.

TODO

Setting up Dagger2 would have been nice, but I haven't found what "a good one looks like" yet for Kotlin.
The MVP implementation is work in progress. It is not currently lifecycle aware
Get the recycler to resort dynamically when is latency sort order.

Retrospective

I decided to make the host list immutable. This is a good thing, but made storing the latency figures (and sorting the Host list) more difficult.
The image for TradeMe redirecting from http to https was a bit of a headache. Forcing OkHttp3 as the Http client solved this.
More unit test coverage would be good.
Using the Kotlin viewbinding for ViewHolders was fiddly. And required turning experimental on. The error handling could be improved. Better feedback.
The UI could use the help of a UX designer...

Third Party Libraries

Google support libs including Constraint-layout Cardview.
Android lifecycle architecture components for the lifecycle aware ViewModel and LiveData
Retrofit2 for Rest/Http calls. Overkill for a single http call, but how I would want to build something bigger out
RxJava2 for async handling. Picasso for image fetching/displaying.
picasso2-okhttp3-downloader to deal with redirect problem caused by TradeMe image redirecting from http to https