Introduction Exploring an Android Open-Source Project: Pokedex

skydoves @github_skydoves Android Developer Advocate @ Stream Jaewoong Eum Google Developer Expert

Open-Source Projects

Open-Source Projects

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Pokedex

Pokedex Main Screen ● Displays a list of Pokemon. Details Screen ● Displays information about a selected Pokemon.

Pokedex github.com/skydoves/pokedex

Tech Stacks

Tech Stacks ● Material Components ● Data Binding (Bindables) ● RecyclerView ● Glide, Palette ● TransformationLayout ● AndroidRibbon, ProgressView, Rainbow User Interface 01

Tech Stacks ● Material Components ● Data Binding (Bindables) ● RecyclerView ● Glide, Palette ● TransformationLayout ● AndroidRibbon, ProgressView, Rainbow User Interface 01 ● Room Database ● Retrofit ● Moshi (Serialization) ● Kotlin Coroutines, Flow ● Sandwich Business Logic 02

Tech Stacks ● Material Components ● Data Binding (Bindables) ● RecyclerView ● Glide, Palette ● TransformationLayout ● AndroidRibbon, ProgressView, Rainbow User Interface 01 ● Room Database ● Retrofit ● Moshi (Serialization) ● Kotlin Coroutines, Flow ● Sandwich Business Logic 02 ● Hilt ● App Startup ● KSP ● Baseline Profiles ● Macrobenchmark Other Jetpacks 03

App Architecture

Architecture Overview

Architecture Overview Unidirectional Data Flow ● Higher layers react to changes in lower layers. ● Events flow down. ● Data flows up with data streams. (Kotlin Flows) Unidirectional Event Flow

Architecture - UI Layer data binding

Architecture - UI Layer data binding Architecture - UI Layer

Architecture - UI Layer data binding

Architecture - UI Layer Transforming streams into bindable data ● View models receive streams of data as Flows from data layers. ● The single flow is converted to a bindable data, which can be observed and updates UI elements. Preserve data across configuration changes ● View models hold data and restore the states of UI elements from configuration changes. Processing user interactions (Unidirectional event flow) ● User actions are communicated from UI elements to view models. ● View models execute business logic following the user interactions.

Architecture - UI Layer developer.android.com/topic/libraries/data-binding

Architecture - UI Layer

class DetailViewModel @AssistedInject constructor( detailRepository: DetailRepository, @Assisted private val pokemonName: String ) : BindingViewModel() { @get:Bindable var isLoading: Boolean by bindingProperty(true) private set private val pokemonInfoFlow: Flow = detailRepository.fetchPokemonInfo( name = pokemonName, onComplete = { isLoading = false }, onError = { toastMessage = it } ) @get:Bindable val pokemonInfo: PokemonInfo? by pokemonInfoFlow.asBindingProperty(viewModelScope, null) DetailViewModel.kt

class DetailViewModel @AssistedInject constructor( detailRepository: DetailRepository, @Assisted private val pokemonName: String ) : BindingViewModel() { @get:Bindable var isLoading: Boolean by bindingProperty(true) private set private val pokemonInfoFlow: Flow = detailRepository.fetchPokemonInfo( name = pokemonName, onComplete = { isLoading = false }, onError = { toastMessage = it } ) @get:Bindable val pokemonInfo: PokemonInfo? by pokemonInfoFlow.asBindingProperty(viewModelScope, null) DetailViewModel.kt

activity_detail.xml

Architecture - Data Layer Persist remote sources into the local database

UI layers must be prepared to react to data changes. Architecture - Data Layer Persist remote sources into the local database

Reads are performed from local storage as the single source of truth. Architecture - Data Layer Persist remote sources into the local database

Architecture - Data Layer A single source of truth principle is a philosophy of aggregating data from many systems within an organization to a single location. developer.android.com/topic/architecture#single-source-of-truth

Architecture - Data Layer Persist remote sources into the local database

interface MainRepository { @WorkerThread fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit): Flow> } internal class MainRepositoryImpl @Inject constructor( .. ) : MainRepository { @WorkerThread override fun fetchPokemonList( page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit ) = flow { .. MainRepository.kt, MainRepositoryImpl.kt

MainRepository.kt, MainRepositoryImpl.kt interface MainRepository { @WorkerThread fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit): Flow> } internal class MainRepositoryImpl @Inject constructor( .. ) : MainRepository { @WorkerThread override fun fetchPokemonList( page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit ) = flow { ..

MainRepositoryImpl.kt @WorkerThread override fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit) = flow { var pokemons = pokemonDao.getPokemonList(page).asDomain() if (pokemons.isEmpty()) { val response = pokedexClient.fetchPokemonList(page = page) response.suspendOnSuccess { pokemons = data.results pokemons.forEach { pokemon -> pokemon.page = page } pokemonDao.insertPokemonList(pokemons.asEntity()) emit(pokemonDao.getAllPokemonList(page).asDomain()) }.onFailure { // handles the all error cases from the API request fails. onError(message()) } } else { emit(pokemonDao.getAllPokemonList(page).asDomain()) } }.onStart { onStart() }.onCompletion { onComplete() }.flowOn(ioDispatcher)

MainRepositoryImpl.kt @WorkerThread override fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit) = flow { var pokemons = pokemonDao.getPokemonList(page).asDomain() if (pokemons.isEmpty()) { val response = pokedexClient.fetchPokemonList(page = page) response.suspendOnSuccess { pokemons = data.results pokemons.forEach { pokemon -> pokemon.page = page } pokemonDao.insertPokemonList(pokemons.asEntity()) emit(pokemonDao.getAllPokemonList(page).asDomain()) }.onFailure { // handles the all error cases from the API request fails. onError(message()) } } else { emit(pokemonDao.getAllPokemonList(page).asDomain()) } }.onStart { onStart() }.onCompletion { onComplete() }.flowOn(ioDispatcher)

MainRepositoryImpl.kt @WorkerThread override fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit) = flow { var pokemons = pokemonDao.getPokemonList(page).asDomain() if (pokemons.isEmpty()) { val response = pokedexClient.fetchPokemonList(page = page) response.suspendOnSuccess { pokemons = data.results pokemons.forEach { pokemon -> pokemon.page = page } pokemonDao.insertPokemonList(pokemons.asEntity()) emit(pokemonDao.getAllPokemonList(page).asDomain()) }.onFailure { // handles the all error cases from the API request fails. onError(message()) } } else { emit(pokemonDao.getAllPokemonList(page).asDomain()) } }.onStart { onStart() }.onCompletion { onComplete() }.flowOn(ioDispatcher)

MainRepositoryImpl.kt @WorkerThread override fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit) = flow { var pokemons = pokemonDao.getPokemonList(page).asDomain() if (pokemons.isEmpty()) { val response = pokedexClient.fetchPokemonList(page = page) response.suspendOnSuccess { pokemons = data.results pokemons.forEach { pokemon -> pokemon.page = page } pokemonDao.insertPokemonList(pokemons.asEntity()) emit(pokemonDao.getAllPokemonList(page).asDomain()) }.onFailure { // handles the all error cases from the API request fails. onError(message()) } } else { emit(pokemonDao.getAllPokemonList(page).asDomain()) } }.onStart { onStart() }.onCompletion { onComplete() }.flowOn(ioDispatcher)

MainRepositoryImpl.kt @WorkerThread override fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit) = flow { var pokemons = pokemonDao.getPokemonList(page).asDomain() if (pokemons.isEmpty()) { val response = pokedexClient.fetchPokemonList(page = page) response.suspendOnSuccess { pokemons = data.results pokemons.forEach { pokemon -> pokemon.page = page } pokemonDao.insertPokemonList(pokemons.asEntity()) emit(pokemonDao.getAllPokemonList(page).asDomain()) }.onFailure { // handles the all error cases from the API request fails. onError(message()) } } else { emit(pokemonDao.getAllPokemonList(page).asDomain()) } }.onStart { onStart() }.onCompletion { onComplete() }.flowOn(ioDispatcher)

Architecture - Data Layer Data Repository Remote DataSource Local DataSource Response Success - body - headers - status code Failure - error body - headers - status code Exception - IOException - UnKnownHostException - SSLHandshakeException - … Error

Architecture - Data Layer Data Repository Remote DataSource Local DataSource Response Success - body - headers - status code Failure - error body - headers - status code Exception - IOException - UnKnownHostException - SSLHandshakeException - … ApiResponse (=Sealed Classes) Error

Architecture - Data Layer Domain Interactors, Use case Interfaces Threading Presentation States View ViewModel Data Repository Remote DataSource Local DataSource Error Error try-catch Success Success

Architecture - Data Layer github.com/skydoves/sandwich getstream.io/blog/modeling-retrofit-responses/

The recommendations and best practices present in this architecture can be applied to a broad spectrum of apps to allow them to scale, improve quality and robustness, and make them easier to test. However, you should treat them as guidelines and adapt them to your requirements as needed. Guide to app architecture developer.android.com/topic/architecture

UI Components

UI Components

UI Components

UI Components

@JvmStatic @BindingAdapter("progressView_labelText") fun bindProgressViewLabelText(progressView: ProgressView, text: String?) { progressView.labelText = text } @JvmStatic @BindingAdapter("progressView_progress") fun bindProgressViewProgress(progressView: ProgressView, value: Int?) { if (value != null) { progressView.progress = value.toFloat() } } ViewBinding.kt activity_detail.xml

UI Components developer.android.com/topic/libraries/data-binding/binding-adapters

App Performance

Baseline Profiles Baseline Profiles

Baseline Profiles

Baseline Profiles

Baseline Profiles Total: 15596 lines (baseline-prof.txt) HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda0;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda0;->onContextAvailable(Landroid/content/Context;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda1;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda1;->saveState()Landroid/os/Bundle; HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda2;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda2;->run()V HSPLandroidx/activity/ComponentActivity$1;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$2;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$3;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$3;->onStateChanged(Landroidx/lifecycle/LifecycleOwner;Landroidx/lifecycle/Lifecycle$Event;)V HSPLandroidx/activity/ComponentActivity$4;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$4;->onStateChanged(Landroidx/lifecycle/LifecycleOwner;Landroidx/lifecycle/Lifecycle$Event;)V HSPLandroidx/activity/ComponentActivity$5;->(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$5;->onStateChanged(Landroidx/lifecycle/LifecycleOwner;Landroidx/lifecycle/Lifecycle$Event;)V HSPLandroidx/activity/ComponentActivity$Api19Impl;->cancelPendingInputEvents(Landroid/view/View;)V HSPLandroidx/activity/ComponentActivity;->()V HSPLandroidx/activity/ComponentActivity;->addMenuProvider(Landroidx/core/view/MenuProvider;)V HSPLandroidx/activity/ComponentActivity;->addOnConfigurationChangedListener(Landroidx/core/util/Consumer;)V ….

Baseline Profiles developer.android.com/topic/performance/baselineprofiles/overview

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