Google Tech Talk DevLibrary - Exploring an Android Open Source Project : Pokedex

In this tech talk, Google Dev Library contributor Jaewoong Eum discusses Pokedex, which follows Google's official Android architecture guidance and demonstrates modern Android development with Hilt, Coroutines, Flow, Jetpack (Room, ViewModel), and Material Design based on MVVM architecture. The repository includes the app's layout, features, functionality, and documentation on how to implement and utilize its resources.

1. Introduction Exploring an Android Open-Source Project: Pokedex
2. skydoves @github_skydoves Android Developer Advocate @ Stream Jaewoong Eum Google Developer Expert
3. Open-Source Projects
4. Open-Source Projects
5. Open-Source Projects Learning Building Sharing
6. Pokedex
7. Pokedex Main Screen • Displays a list of Pokemon. Details Screen • Displays information about a selected Pokemon.
8. Pokedex github.com/skydoves/pokedex
9. Tech Stacks
10. Tech Stacks • Material Components • Data Binding (Bindables) • RecyclerView • Glide, Palette • TransformationLayout • AndroidRibbon, ProgressView, Rainbow User Interface 01
11. 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
12. 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
13. App Architecture
14. Architecture Overview
15. 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
16. Architecture - UI Layer data binding
17. Architecture - UI Layer data binding Architecture - UI Layer
18. Architecture - UI Layer data binding
19. 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.
20. Architecture - UI Layer developer.android.com/topic/libraries/data-binding
21. Architecture - UI Layer
22. 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<PokemonInfo?> = detailRepository.fetchPokemonInfo( name = pokemonName, onComplete = { isLoading = false }, onError = { toastMessage = it } ) @get:Bindable val pokemonInfo: PokemonInfo? by pokemonInfoFlow.asBindingProperty(viewModelScope, null) DetailViewModel.kt
23. 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<PokemonInfo?> = detailRepository.fetchPokemonInfo( name = pokemonName, onComplete = { isLoading = false }, onError = { toastMessage = it } ) @get:Bindable val pokemonInfo: PokemonInfo? by pokemonInfoFlow.asBindingProperty(viewModelScope, null) DetailViewModel.kt
24. <androidx.appcompat.widget.AppCompatImageView android:id="@+id/image" android:layout_width="190dp" android:layout_height="190dp" android:layout_marginBottom="20dp" android:scaleType="center" android:translationZ="100dp" app:layout_constraintBottom_toBottomOf="@id/header" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:paletteImage="@{pokemon.imageUrl}" app:paletteView="@{header}" /> activity_detail.xml <com.skydoves.progressview.ProgressView android:id="@+id/progress_hp" android:layout_width="0dp" android:layout_height="18dp" android:layout_marginStart="32dp" android:layout_marginEnd="32dp" app:layout_constraintBottom_toBottomOf="@id/hp" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toEndOf="@id/hp" app:layout_constraintTop_toTopOf="@id/hp" app:progressView_colorBackground="@color/white" app:progressView_colorProgress="@color/colorPrimary" app:progressView_labelColorInner="@color/white" app:progressView_labelColorOuter="@color/black" app:progressView_labelSize="12sp" app:progressView_labelText="@{vm.pokemonInfo.hpString}" app:progressView_max="@{vm.pokemonInfo.maxHp}" app:progressView_progress="@{vm.pokemonInfo.hp}" app:progressView_radius="12dp" />
25. Architecture - Data Layer Persist remote sources into the local database
26. UI layers must be prepared to react to data changes. Architecture - Data Layer Persist remote sources into the local database
27. Reads are performed from local storage as the single source of truth. Architecture - Data Layer Persist remote sources into the local database
28. 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
29. Architecture - Data Layer Persist remote sources into the local database
30. interface MainRepository { @WorkerThread fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit): Flow<List<Pokemon>> } internal class MainRepositoryImpl @Inject constructor( .. ) : MainRepository { @WorkerThread override fun fetchPokemonList( page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit ) = flow { .. MainRepository.kt, MainRepositoryImpl.kt
31. MainRepository.kt, MainRepositoryImpl.kt interface MainRepository { @WorkerThread fun fetchPokemonList(page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit): Flow<List<Pokemon>> } internal class MainRepositoryImpl @Inject constructor( .. ) : MainRepository { @WorkerThread override fun fetchPokemonList( page: Int, onStart: () -> Unit, onComplete: () -> Unit, onError: (String?) -> Unit ) = flow { ..
32. 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)
33. 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)
34. 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)
35. 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)
36. 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)
37. 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
38. 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
39. 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
40. Architecture - Data Layer github.com/skydoves/sandwich getstream.io/blog/modeling-retrofit-responses/
41. 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
42. UI Components
43. UI Components
44. UI Components
45. UI Components
46. @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 <com.skydoves.progressview.ProgressView android:id="@+id/progress_hp" android:layout_width="0dp" android:layout_height="18dp" android:layout_marginStart="32dp" android:layout_marginEnd="32dp" app:layout_constraintBottom_toBottomOf="@id/hp" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toEndOf="@id/hp" app:layout_constraintTop_toTopOf="@id/hp" app:progressView_colorBackground="@color/white" app:progressView_colorProgress="@color/colorPrimary" app:progressView_labelColorInner="@color/white" app:progressView_labelColorOuter="@color/black" app:progressView_labelSize="12sp" app:progressView_labelText="@{vm.pokemonInfo.hpString}" app:progressView_max="@{vm.pokemonInfo.maxHp}" app:progressView_progress="@{vm.pokemonInfo.hp}" app:progressView_radius="12dp" /> activity_detail.xml
47. UI Components developer.android.com/topic/libraries/data-binding/binding-adapters
48. App Performance
49. Baseline Profiles Baseline Profiles
50. Baseline Profiles
51. Baseline Profiles
52. Baseline Profiles Total: 15596 lines (baseline-prof.txt) HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda0;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda0;->onContextAvailable(Landroid/content/Context;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda1;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda1;->saveState()Landroid/os/Bundle; HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda2;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$$ExternalSyntheticLambda2;->run()V HSPLandroidx/activity/ComponentActivity$1;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$2;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$3;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$3;->onStateChanged(Landroidx/lifecycle/LifecycleOwner;Landroidx/lifecycle/Lifecycle$Event;)V HSPLandroidx/activity/ComponentActivity$4;-><init>(Landroidx/activity/ComponentActivity;)V HSPLandroidx/activity/ComponentActivity$4;->onStateChanged(Landroidx/lifecycle/LifecycleOwner;Landroidx/lifecycle/Lifecycle$Event;)V HSPLandroidx/activity/ComponentActivity$5;-><init>(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;-><init>()V HSPLandroidx/activity/ComponentActivity;->addMenuProvider(Landroidx/core/view/MenuProvider;)V HSPLandroidx/activity/ComponentActivity;->addOnConfigurationChangedListener(Landroidx/core/util/Consumer;)V ….
53. Baseline Profiles developer.android.com/topic/performance/baselineprofiles/overview
54. Open-Source Projects Build your open-source project!
55. Google Dev Library devlibrary.withgoogle.com/
56. GitHub Trending github.com/trending
57. Thank you!