SimpleMVI

Lightweight Android MVI library for uni-directional architecture.

The goal is to provide a set of APIs and interfaces that can conveniently setup a complex screen with many different states in a highly structured manner.

What is MVI?

MVI is a uni-directional architecture for Android.

This library takes a simplified & practical approach for configuring MVI for real-world cases.

          Intent                       Result                    ViewState
 MviView --------> MviProcessorHolder --------> MviReducerHolder ----------> MviView
             |                                                        |
             ---------------------- MviViewModel ----------------------

Explained well in this video : https://www.youtube.com/watch?v=64rQ9GKphTg (Benoît Quenaudon)

Setup

Gradle

From jcenter :

implementation 'com.trent.simplemvi:simplemvi:0.9.4'

RxJava 2 is required.

How to use

Initial Setup

Let's say we want to create a screen with name Main.

Start by creating sealed class for each of the required components, Intent, Result and ViewState.

sealed class MainIntent : MviIntent

sealed class MainResult : MviResult

sealed class MainViewState : MviViewState

Also create other classes that implement MviProcessorHolder, MviReducerHolder.

class MainProcessorHolder(model: MainModel) : MviProcessorHolder<MainIntent, MainResult>

class MainReducerHolder : MviReducerHolder<MainResult, MainViewState>

Create a ViewModel & View as well.

class MainViewModel(
  processorHolder: MviProcessorHolder<MainIntent, MainResult>,
  reducerHolder: MviReducerHolder<MainResult, MainViewState>
  ) : MviViewModel<MainIntent, MainResult, MainViewState>(processorHolder, reducerHolder)

class MainView(
  containerView: View, viewModel: MainViewModel
  ) : MviView<MainIntent, MainResult, MainViewState>(viewModel)

In your Activity or Fragment, initialize at Activity onCreate() with code similar to this.

viewModel = ViewModelProviders.of(
  this,
  MviViewModelFactory(
    MainProcessorHolder(MainModel()),
    MainReducerHolder()
  )
).get(MainViewModel::class.java)

MainView(this.view, viewModel).apply {
  lifecycle.addObserver(this)
  setup()
}

You may need more methods & parameters for your classes depending on how you initialize your View references etc.

Use MviActivity or MviFragment for faster setup.

Configuration Workflow

Whichever way you go about configuring MVI is fine, I usually go back and forth, but generally I do this. I recommend you to find your workflow as well.

1. Draw XML layouts.
2. Sketch possible states of the view with ViewState.
3. Configure render() method of MainView such that view is drawn correctly according to ViewState.
4. Sketch possible actions that user will take to change the view with Intent.
5. Configure callbacks such as View.setOnClickListener() correctly such that user actions will trigger correct Intent to intentsSubject, passing it to MainProcessorHolder.
6. Implement Result & MainProcessorHolder such that Intent can produce correct Result. Handle side-effects such as DB & Networking while processing intents as well. This result will be passed to MainReducerHolder.
7. Implement MainReducerHolder such that Result will produce correct ViewState in combination with previous ViewState. This resulting view state will be passed to MainView, and the new view state will be rendered.

After initial configuration, you will find that modification is a breeze.

See sampleapp module for detailed recommended usage.