Nessa apresentação demonstro como arquitetar uma aplicação Android utilizando MVVM+Clean Architecture no Android utilizando as bibliotecas do Jetpack (View Model, Room, LiveData, ...)

1. Arquitetando seu app
Android com Jetpack
Nelson Glauber
@nglauber

2. Porque devemos nos
preocupar com arquitetura?
‣ Diversos tipos de negócios estão sendo feitos pelo
celular. Muitos deles são mobile first.
‣ A complexidade dos aplicativos está cada dia maior.
‣ Por isso o código tem que ser robusto, testável e
deve facilitar a manutenção e a adição de
funcionalidades.
‣ Atualmente existem diversos frameworks para ajudar
nessas tarefas, mas eles são suficientes?

3. Porque devemos nos
preocupar com arquitetura?
‣ Frameworks forçam o desenvolvedor a seguir o
próprio framework e não os princípios da
engenharia de software.
‣ É preciso ter uma arquitetura que deixe claro o
propósito do sistema, não os frameworks utilizados.
‣ A lógica de negócio deve estar claramente separada e
independente de framework.

4. Arquitetura
‣ Regra Principal: não há regras. Mas existem princípios que
devem ser seguidos. Lembra do S.O.L.I.D.?
‣ Promove a organização e o desacoplamento do código.
‣ Deve facilitar a manutenção e a adição de funcionalidades.
‣ Uma arquitetura deve ser testável!
‣ Ela incrementa a complexidade? Sim!
Vale à pena? Com certeza! 😎
Mas deve ser de conhecimento de toda à equipe.
Single Responsibility Principle
Open-Closed Principle
Liskov Substitution Principle
Interface Segregation Principle
Dependency Inversion Principle

5. MVP
Model View Presenter
View
IView
Presenter Model
User interaction Request
DataUI Logic
implements
IPresenter
implements

6. VIEW
Fragment
PRESENTER
Activity
REPOSITORY
Remote
Data Source
Local
Data Source

7. MVVM
Model View View-Model
View ViewModel Model
Observes
User interaction
Data
Request

8. VIEW
Fragment
VIEWMODEL
Activity
REPOSITORY
Remote
Data Source
Local
Data Source
Data
Binding

10. https://fernandocejas.com/2014/09/03/architecting-android-the-clean-way/

11. androidx.*

14. https://github.com/nglauber/books_jetpack/

15. UI (app)
Presentation
Domain
Remote Local
Data

16. UI (app)
Presentation
Domain
Remote Local
Data

17. Data
• Módulo Kotlin.
• Normalmente contém
classes de dados e
interfaces.
• Decisão importante aqui:
esse app será reativo?
🤔
Data

18. RX Java

19. Coroutines Flow
https://bit.ly/2KwSkDs

20. interface BooksRepository {
fun loadBooks(): Flow<List<Book>>
fun loadBook(bookId: String): Flow<Book>
suspend fun saveBook(book: Book)
suspend fun remove(book: Book)
}

21. interface BooksRepository {
fun loadBooks(): Flow<List<Book>>
fun loadBook(bookId: String): Flow<Book>
suspend fun saveBook(book: Book)
suspend fun remove(book: Book)
}

22. interface BooksRepository {
fun loadBooks(): Flow<List<Book>>
fun loadBook(bookId: String): Flow<Book>
suspend fun saveBook(book: Book)
suspend fun remove(book: Book)
}

23. UI (app)
Presentation
Domain
Remote Local
Data

24. Data - Local
• Módulo Android
• Faz a implementação do
repositório local.
• A classe Book deste
módulo é diferente da
classe Book do módulo
data.
Local

25. Room
• ORM (Object-Relational
Mapping) para SQLite.
• Suporta live updates por
meio de:
• LiveData
• RXJava
(Observable/Flowable)
• Coroutines
(flow)
Local

27. @Entity
@TypeConverters(MediaTypeConverter::class)
data class Book(
@PrimaryKey
var id: String,
var title: String = "",
var author: String = "",
var coverUrl: String = "",
var pages: Int = 0,
var year: Int = 0,
@Embedded(prefix = "publisher_")
var publisher: Publisher,
var available: Boolean = false,
var mediaType: MediaType = MediaType.PAPER,
var rating: Float = 0f
)

28. @Entity
@TypeConverters(MediaTypeConverter::class)
data class Book(
@PrimaryKey
var id: String,
var title: String = "",
var author: String = "",
var coverUrl: String = "",
var pages: Int = 0,
var year: Int = 0,
@Embedded(prefix = "publisher_")
var publisher: Publisher,
var available: Boolean = false,
var mediaType: MediaType = MediaType.PAPER,
var rating: Float = 0f
)

29. @Dao
interface BookDao {
@Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun save(book: Book)
@Delete
suspend fun delete(vararg book: Book)
@Query("SELECT * FROM Book WHERE title LIKE :title ORDER BY title")
fun bookByTitle(title: String = "%"): Flow<List<Book>>
@Query("SELECT * FROM Book WHERE id = :id")
fun bookById(id: String): Flow<Book>
}

30. @Database(entities = [Book::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun bookDao(): BookDao
companion object {
private var instance: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
if (instance == null) {
instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"booksDb")
.build()
}
return instance as AppDatabase
}
}
}

31. @Database(entities = [Book::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun bookDao(): BookDao
companion object {
private var instance: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
if (instance == null) {
instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"booksDb")
.build()
}
return instance as AppDatabase
}
}
}

32. @Database(entities = [Book::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun bookDao(): BookDao
companion object {
private var instance: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
if (instance == null) {
instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"booksDb")
.build()
}
return instance as AppDatabase
}
}
}

33. @Database(entities = [Book::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun bookDao(): BookDao
companion object {
private var instance: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
if (instance == null) {
instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"booksDb")
.build()
}
return instance as AppDatabase
}
}
}

34. class RoomRepository(
db: AppDatabase,
private val fileHelper: FileHelper
) : BooksRepository {
private val bookDao = db.bookDao()
override suspend fun saveBook(book: Book) {
if (book.id.isBlank()) {
book.id = UUID.randomUUID().toString()
}
return if (fileHelper.saveCover(book)) {
bookDao.save(BookConverter.fromData(book))
} else {
throw RuntimeException("Error saving book's cover.")
}
}
...

35. class RoomRepository(
db: AppDatabase,
private val fileHelper: FileHelper
) : BooksRepository {
private val bookDao = db.bookDao()
override suspend fun saveBook(book: Book) {
if (book.id.isBlank()) {
book.id = UUID.randomUUID().toString()
}
return if (fileHelper.saveCover(book)) {
bookDao.save(BookConverter.fromData(book))
} else {
throw RuntimeException("Error saving book's cover.")
}
}
...

36. class RoomRepository(
db: AppDatabase,
private val fileHelper: FileHelper
) : BooksRepository {
private val bookDao = db.bookDao()
override suspend fun saveBook(book: Book) {
if (book.id.isBlank()) {
book.id = UUID.randomUUID().toString()
}
return if (fileHelper.saveCover(book)) {
bookDao.save(BookConverter.fromData(book))
} else {
throw RuntimeException("Error saving book's cover.")
}
}
...

37. class RoomRepository(
db: AppDatabase,
private val fileHelper: FileHelper
) : BooksRepository {
private val bookDao = db.bookDao()
override fun loadBooks(): Flow<List<Book>> {
return bookDao.bookByTitle()
.map { books ->
books.map { book ->
BookConverter.toData(book)
}
}
}
...

38. UI (app)
Presentation
Domain
Remote Local
Data

39. Domain
• Módulo Kotlin
• Implementação da lógica
de negócio maneira
abstrata.
Domain

40. open class ListBooksUseCase(
private val repository: BooksRepository
) {
fun execute(): Flow<List<Book>> {
return repository.loadBooks()
}
}

41. open class SaveBookUseCase(
private val repository: BooksRepository
) {
suspend fun execute(params: Book) {
return if (bookIsValid(params)) {
repository.saveBook(params)
} else {
throw IllegalArgumentException("Book is not valid")
}
}
private fun bookIsValid(book: Book): Boolean {
return (
book.title.isNotBlank() &&
book.author.isNotBlank() &&
book.pages > 0 &&
book.year > 1900 &&
book.year <= Calendar.getInstance().get(Calendar.YEAR)
)
}
}

42. open class SaveBookUseCase(
private val repository: BooksRepository
) {
suspend fun execute(params: Book) {
return if (bookIsValid(params)) {
repository.saveBook(params)
} else {
throw IllegalArgumentException("Book is not valid")
}
}
private fun bookIsValid(book: Book): Boolean {
return (
book.title.isNotBlank() &&
book.author.isNotBlank() &&
book.pages > 0 &&
book.year > 1900 &&
book.year <= Calendar.getInstance().get(Calendar.YEAR)
)
}
}

43. open class SaveBookUseCase(
private val repository: BooksRepository
) {
suspend fun execute(params: Book) {
return if (bookIsValid(params)) {
repository.saveBook(params)
} else {
throw IllegalArgumentException("Book is not valid")
}
}
private fun bookIsValid(book: Book): Boolean {
return (
book.title.isNotBlank() &&
book.author.isNotBlank() &&
book.pages > 0 &&
book.year > 1900 &&
book.year <= Calendar.getInstance().get(Calendar.YEAR)
)
}
}

44. open class SaveBookUseCase(
private val repository: BooksRepository
) {
suspend fun execute(params: Book) {
return if (bookIsValid(params)) {
repository.saveBook(params)
} else {
throw IllegalArgumentException("Book is not valid")
}
}
private fun bookIsValid(book: Book): Boolean {
return (
book.title.isNotBlank() &&
book.author.isNotBlank() &&
book.pages > 0 &&
book.year > 1900 &&
book.year <= Calendar.getInstance().get(Calendar.YEAR)
)
}
}

45. UI (app)
Presentation
Domain
Remote Local
Data

46. Data Binding
• Torna fácil a ligação
entre a View e o
ViewModel (ou
Presenter).
• Permite estender
arquivos de layout com
micro-expressões.
• Particularmente útil em
telas onde há input de
dados.
Presentation

48. @Parcelize
class Book : BaseObservable(), Parcelable {
@Bindable
var id: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.id)
}
@Bindable
var title: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.title)
}
// demais atributos
}

49. @Parcelize
class Book : BaseObservable(), Parcelable {
@Bindable
var id: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.id)
}
@Bindable
var title: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.title)
}
// demais atributos
}

50. @Parcelize
class Book : BaseObservable(), Parcelable {
@Bindable
var id: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.id)
}
@Bindable
var title: String = ""
set(value) {
field = value
notifyPropertyChanged(BR.title)
}
// demais atributos
}

51. <layout ...>
<data> ...
<import type="dominando.android.presentation.binding.MediaType" />
<variable name="book" type="dominando.android.presentation.binding.Book" />
<variable name=“formView" type="dominando.android.livros.BookFragment" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout ...>
<ImageView android:src="@{book.coverUrl}" ...
android:onClick="@{formView::clickTakePhoto}"/>
<EditText android:text="@={book.title}" ... />
<EditText android:text="@={book.author}" ... />
<EditText android:text="@={book.pages}" ... />
<EditText android:text="@={book.year}" ... />
<Spinner ...>
<CheckBox android:checked="@={book.available}" ... />
<RadioGroup ...>
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.EBOOK}" ... />
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.PAPER}" ... />
</RadioGroup>
<RatingBar android:rating="@={book.rating}" ... />
<Button android:onClick="@{formView::clickSaveBook}" .../>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
res/layout/fragment_book_form.xml

52. <layout ...>
<data> ...
<import type="dominando.android.presentation.binding.MediaType" />
<variable name="book" type="dominando.android.presentation.binding.Book" />
<variable name="formView" type="dominando.android.livros.BookFragment" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout ...>
<ImageView android:src="@{book.coverUrl}" ...
android:onClick="@{formView::clickTakePhoto}"/>
<EditText android:text="@={book.title}" ... />
<EditText android:text="@={book.author}" ... />
<EditText android:text="@={book.pages}" ... />
<EditText android:text="@={book.year}" ... />
<Spinner ...>
<CheckBox android:checked="@={book.available}" ... />
<RadioGroup ...>
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.EBOOK}" ... />
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.PAPER}" ... />
</RadioGroup>
<RatingBar android:rating="@={book.rating}" ... />
<Button android:onClick="@{formView::clickSaveBook}" .../>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
res/layout/fragment_book_form.xml

53. <layout ...>
<data> ...
<import type="dominando.android.presentation.binding.MediaType" />
<variable name="book" type="dominando.android.presentation.binding.Book" />
<variable name="formView" type="dominando.android.livros.BookFragment" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout ...>
<ImageView android:src="@{book.coverUrl}" ...
android:onClick="@{formView::clickTakePhoto}"/>
<EditText android:text="@={book.title}" ... />
<EditText android:text="@={book.author}" ... />
<EditText android:text="@={book.pages}" ... />
<EditText android:text="@={book.year}" ... />
<Spinner ...>
<CheckBox android:checked="@={book.available}" ... />
<RadioGroup ...>
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.EBOOK}" ... />
<RadioButton ...
android:checked="@{book.mediaTypeValue == MediaType.PAPER}" ... />
</RadioGroup>
<RatingBar android:rating="@={book.rating}" ... />
<Button android:onClick="@{formView::clickSaveBook}" .../>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
res/layout/fragment_book_form.xml

54. class BookFormFragment : BaseFragment() {
private lateinit var binding: FragmentBookFormBinding
override fun onCreateView ... {
binding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_book_form,
container,
false
)
return binding.root
}
override fun onViewCreated ... {
binding.book = viewModel.book
binding.formView = this
}
...

55. class BookFormFragment : BaseFragment() {
private lateinit var binding: FragmentBookFormBinding
override fun onCreateView ... {
binding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_book_form,
container,
false
)
return binding.root
}
override fun onViewCreated ... {
binding.book = viewModel.book
binding.formView = this
}
...

56. class BookFormFragment : BaseFragment() {
private lateinit var binding: FragmentBookFormBinding
override fun onCreateView ... {
binding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_book_form,
container,
false
)
return binding.root
}
override fun onViewCreated ... {
binding.book = viewModel.book
binding.formView = this
}
...

57. class BookFormFragment : BaseFragment() {
private lateinit var binding: FragmentBookFormBinding
override fun onCreateView ... {
binding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_book_form,
container,
false
)
return binding.root
}
override fun onViewCreated ... {
binding.book = viewModel.book
binding.formView = this
}
...

58. ViewModel Presentation
• Mantém a lógica de
apresentação.
• Recebe as ações da
view.
• Fornece dados
observáveis para view.
• Sobrevive às mudanças
de configuração.

59. ViewModel Presentation

60. LiveData
• Armazena dados observáveis
(Observable) e notifica os
observadores (Observer)
quando esses dados são
modificados permitindo que
UI seja atualizada.
• LiveData é lifecycle-aware,
o que significa que os
observadores só serão
notificados se a Activity/
Fragment estiver no estado
de STARTED ou RESUMED.
Presentation

61. class BookDetailsViewModel(private val useCase: ViewBookDetailsUseCase) : ViewModel() {
private val state: MutableLiveData<ViewState<BookBinding>> = MutableLiveData()
fun getState(): LiveData<ViewState<BookBinding>> = state
fun loadBook(id: String) {
...
viewModelScope.launch {
state.postValue(ViewState(ViewState.Status.LOADING))
try {
useCase.execute(id).collect { book ->
if (book != null) {
val bookBinding = BookConverter.fromData(book)
state.postValue(ViewState(ViewState.Status.SUCCESS, bookBinding))
} else {
state.postValue(
ViewState(ViewState.Status.ERROR, RuntimeException("Book not found"))
)
}
}
} catch (e: Exception) {
state.postValue(ViewState(ViewState.Status.ERROR, error = e))
}
}
}

62. class BookDetailsViewModel(private val useCase: ViewBookDetailsUseCase) : ViewModel() {
private val state: MutableLiveData<ViewState<BookBinding>> = MutableLiveData()
fun getState(): LiveData<ViewState<BookBinding>> = state
fun loadBook(id: String) {
...
viewModelScope.launch {
state.postValue(ViewState(ViewState.Status.LOADING))
try {
useCase.execute(id).collect { book ->
if (book != null) {
val bookBinding = BookConverter.fromData(book)
state.postValue(ViewState(ViewState.Status.SUCCESS, bookBinding))
} else {
state.postValue(
ViewState(ViewState.Status.ERROR, RuntimeException("Book not found"))
)
}
}
} catch (e: Exception) {
state.postValue(ViewState(ViewState.Status.ERROR, error = e))
}
}
}

63. class BookDetailsViewModel(private val useCase: ViewBookDetailsUseCase) : ViewModel() {
private val state: MutableLiveData<ViewState<BookBinding>> = MutableLiveData()
fun getState(): LiveData<ViewState<BookBinding>> = state
fun loadBook(id: String) {
...
viewModelScope.launch {
state.postValue(ViewState(ViewState.Status.LOADING))
try {
useCase.execute(id).collect { book ->
if (book != null) {
val bookBinding = BookConverter.fromData(book)
state.postValue(ViewState(ViewState.Status.SUCCESS, bookBinding))
} else {
state.postValue(
ViewState(ViewState.Status.ERROR, RuntimeException("Book not found"))
)
}
}
} catch (e: Exception) {
state.postValue(ViewState(ViewState.Status.ERROR, error = e))
}
}
}

64. class BookDetailsViewModel(private val useCase: ViewBookDetailsUseCase) : ViewModel() {
private val state: MutableLiveData<ViewState<BookBinding>> = MutableLiveData()
fun getState(): LiveData<ViewState<BookBinding>> = state
fun loadBook(id: String) {
...
viewModelScope.launch {
state.postValue(ViewState(ViewState.Status.LOADING))
try {
useCase.execute(id).collect { book ->
if (book != null) {
val bookBinding = BookConverter.fromData(book)
state.postValue(ViewState(ViewState.Status.SUCCESS, bookBinding))
} else {
state.postValue(
ViewState(ViewState.Status.ERROR, RuntimeException("Book not found"))
)
}
}
} catch (e: Exception) {
state.postValue(ViewState(ViewState.Status.ERROR, error = e))
}
}
}

65. class BookDetailsFragment : BaseFragment() {
private val viewModel: BookDetailsViewModel by viewModels {
BookVmFactory(requireActivity().application)
}
…
private fun init() {
viewModel.getState().observe(viewLifecycleOwner, Observer { viewState ->
when (viewState.status) {
ViewState.Status.SUCCESS -> binding.book = viewState.data
ViewState.Status.LOADING -> {} /* Exibir Loading */
ViewState.Status.ERROR -> {} /* Exibir Erro */
}
})
val book = arguments?.getParcelable<Book>("book")
book?.let {
viewModel.loadBook(book.id)
}
}

66. class BookDetailsFragment : BaseFragment() {
private val viewModel: BookDetailsViewModel by viewModels {
BookVmFactory(requireActivity().application)
}
…
private fun init() {
viewModel.getState().observe(viewLifecycleOwner, Observer { viewState ->
when (viewState.status) {
ViewState.Status.SUCCESS -> binding.book = viewState.data
ViewState.Status.LOADING -> {} /* Exibir Loading */
ViewState.Status.ERROR -> {} /* Exibir Erro */
}
})
val book = arguments?.getParcelable<Book>("book")
book?.let {
viewModel.loadBook(book.id)
}
}

67. class BookDetailsFragment : BaseFragment() {
private val viewModel: BookDetailsViewModel by viewModels {
BookVmFactory(requireActivity().application)
}
…
private fun init() {
viewModel.getState().observe(viewLifecycleOwner, Observer { viewState ->
when (viewState.status) {
ViewState.Status.SUCCESS -> binding.book = viewState.data
ViewState.Status.LOADING -> {} /* Exibir Loading */
ViewState.Status.ERROR -> {} /* Exibir Erro */
}
})
val book = arguments?.getParcelable<Book>("book")
book?.let {
viewModel.loadBook(book.id)
}
}

68. class BookDetailsFragment : BaseFragment() {
private val viewModel: BookDetailsViewModel by viewModels {
BookVmFactory(requireActivity().application)
}
…
private fun init() {
viewModel.getState().observe(viewLifecycleOwner, Observer { viewState ->
when (viewState.status) {
ViewState.Status.SUCCESS -> binding.book = viewState.data
ViewState.Status.LOADING -> {} /* Exibir Loading */
ViewState.Status.ERROR -> {} /* Exibir Erro */
}
})
val book = arguments?.getParcelable<Book>("book")
book?.let {
viewModel.loadBook(book.id)
}
}

69. Presentation
open class LiveEvent<out T>(private val content: T) {
var hasBeenConsumed = false
private set
fun consumeEvent(): T? {
return if (hasBeenConsumed) {
null
} else {
hasBeenConsumed = true
content
}
}
fun peekContent(): T = content
}

70. class BookFormViewModel(
private val useCase: SaveBookUseCase
) : ViewModel(), LifecycleObserver {
private val state: MutableLiveData<LiveEvent<ViewState<Unit>>> = MutableLiveData()
fun getState(): LiveData<LiveEvent<ViewState<Unit>>> = state
fun saveBook(book: BookBinding) {
state.postValue(LiveEvent(ViewState(ViewState.Status.LOADING)))
viewModelScope.launch {
try {
withContext(Dispatchers.IO) {
useCase.execute(BookConverter.toData(book))
}
state.postValue(LiveEvent(ViewState(ViewState.Status.SUCCESS)))
} catch (e: Exception) {
state.postValue(LiveEvent(ViewState(ViewState.Status.ERROR, error = e)))
}
}
}

71. class BookFormViewModel(
private val useCase: SaveBookUseCase
) : ViewModel(), LifecycleObserver {
private val state: MutableLiveData<LiveEvent<ViewState<Unit>>> = MutableLiveData()
fun getState(): LiveData<LiveEvent<ViewState<Unit>>> = state
fun saveBook(book: BookBinding) {
state.postValue(LiveEvent(ViewState(ViewState.Status.LOADING)))
viewModelScope.launch {
try {
withContext(Dispatchers.IO) {
useCase.execute(BookConverter.toData(book))
}
state.postValue(LiveEvent(ViewState(ViewState.Status.SUCCESS)))
} catch (e: Exception) {
state.postValue(LiveEvent(ViewState(ViewState.Status.ERROR, error = e)))
}
}
}

72. class BookFormViewModel(
private val useCase: SaveBookUseCase
) : ViewModel(), LifecycleObserver {
private val state: MutableLiveData<LiveEvent<ViewState<Unit>>> = MutableLiveData()
fun getState(): LiveData<LiveEvent<ViewState<Unit>>> = state
fun saveBook(book: BookBinding) {
state.postValue(LiveEvent(ViewState(ViewState.Status.LOADING)))
viewModelScope.launch {
try {
withContext(Dispatchers.IO) {
useCase.execute(BookConverter.toData(book))
}
state.postValue(LiveEvent(ViewState(ViewState.Status.SUCCESS)))
} catch (e: Exception) {
state.postValue(LiveEvent(ViewState(ViewState.Status.ERROR, error = e)))
}
}
}

73. class BookFormViewModel(
private val useCase: SaveBookUseCase
) : ViewModel(), LifecycleObserver {
private val state: MutableLiveData<LiveEvent<ViewState<Unit>>> = MutableLiveData()
fun getState(): LiveData<LiveEvent<ViewState<Unit>>> = state
fun saveBook(book: BookBinding) {
state.postValue(LiveEvent(ViewState(ViewState.Status.LOADING)))
viewModelScope.launch {
try {
withContext(Dispatchers.IO) {
useCase.execute(BookConverter.toData(book))
}
state.postValue(LiveEvent(ViewState(ViewState.Status.SUCCESS)))
} catch (e: Exception) {
state.postValue(LiveEvent(ViewState(ViewState.Status.ERROR, error = e)))
}
}
}

74. class BookFormFragment : BaseFragment() {
...
private fun init() {
viewModel.getState().observe(this, Observer { event ->
event?.peekContent()?.let { state ->
when (state.status) {
ViewState.Status.LOADING -> {...}
ViewState.Status.SUCCESS -> {...}
ViewState.Status.ERROR -> {
...
event.consumeEvent()
}
}
}
})
}

75. class BookFormFragment : BaseFragment() {
...
private fun init() {
viewModel.getState().observe(this, Observer { event ->
event?.peekContent()?.let { state ->
when (state.status) {
ViewState.Status.LOADING -> {...}
ViewState.Status.SUCCESS -> {...}
ViewState.Status.ERROR -> {
...
event.consumeEvent()
}
}
}
})
}

76. Lifecycle
• Lifecycle é um objeto que define um ciclo de vida.
• LifecycleOwner é a interface a ser implementada por
objetos que que possuem um ciclo de vida.
• Activity e Fragment implementam LifecycleOwner e
têm Lifecycle.
• LifecycleObserver é a interface a ser implementada
pela classe que deseja observar o ciclo de vida de
um LifecycleOwner.

77. class BookListViewModel(
private val loadBooksUseCase: ListBooksUseCase, ...
) : ViewModel(), LifecycleObserver {
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
fun loadBooks() {
...
}

78. class BookListFragment : BaseFragment() {
private val viewModel: BookListViewModel
private fun init() {
...
lifecycle.addObserver(viewModel)
}
...

79. UI (app)
Presentation
Domain
Remote Local
Data

80. Navigation API
• Introduz o paradigma de Single
Activity.
• Representação visual do fluxo de
telas.
• Centraliza a lógica de
navegação da aplicação.
• Permite a conexão direta com
componentes de UI como:
ActionBar, Button, Menu,
BottomNav, …
• Simplifica a passagem e
atribuição de parâmetros.
UI (app)

82. <navigation ...
android:id="@+id/main_graph"
app:startDestination="@id/signInFragment">
<fragment
android:id="@+id/listBooks"
android:name="dominando.android.livros.BookListFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_list">
<action
android:id="@+id/action_list_to_form"
app:destination="@id/formBook" ... />
...
</fragment>
<fragment
android:id="@+id/bookDetails"
android:name="dominando.android.livros.BookDetailsFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_details">
...
<argument
android:name="book"
app:argType="dominando.android.presentation.binding.Book"
app:nullable="true" />
</fragment>

83. <navigation ...
android:id="@+id/main_graph"
app:startDestination="@id/signInFragment">
<fragment
android:id="@+id/listBooks"
android:name="dominando.android.livros.BookListFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_list">
<action
android:id="@+id/action_list_to_form"
app:destination="@id/formBook" ... />
...
</fragment>
<fragment
android:id="@+id/bookDetails"
android:name="dominando.android.livros.BookDetailsFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_details">
...
<argument
android:name="book"
app:argType="dominando.android.presentation.binding.Book"
app:nullable="true" />
</fragment>

84. <navigation ...
android:id="@+id/main_graph"
app:startDestination="@id/signInFragment">
<fragment
android:id="@+id/listBooks"
android:name="dominando.android.livros.BookListFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_list">
<action
android:id="@+id/action_list_to_form"
app:destination="@id/formBook" ... />
...
</fragment>
<fragment
android:id="@+id/bookDetails"
android:name="dominando.android.livros.BookDetailsFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_details">
...
<argument
android:name="book"
app:argType="dominando.android.presentation.binding.Book"
app:nullable="true" />
</fragment>

85. <navigation ...
android:id="@+id/main_graph"
app:startDestination="@id/signInFragment">
<fragment
android:id="@+id/listBooks"
android:name="dominando.android.livros.BookListFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_list">
<action
android:id="@+id/action_list_to_form"
app:destination="@id/formBook" ... />
...
</fragment>
<fragment
android:id="@+id/bookDetails"
android:name="dominando.android.livros.BookDetailsFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_book_details">
...
<argument
android:name="book"
app:argType="dominando.android.presentation.binding.Book"
app:nullable="true" />
</fragment>

86. <FrameLayout ...>
<fragment
android:id="@+id/navHost"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:navGraph="@navigation/nav_graph"
app:defaultNavHost="true" />
</FrameLayout>

87. class BookActivity : AppCompatActivity() {
private val navController: NavController by lazy {
Navigation.findNavController(this, R.id.navHost)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_book)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}

88. class BookActivity : AppCompatActivity() {
private val navController: NavController by lazy {
Navigation.findNavController(this, R.id.navHost)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_book)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}

89. class BookActivity : AppCompatActivity() {
private val navController: NavController by lazy {
Navigation.findNavController(this, R.id.navHost)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_book)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}

90. class BookActivity : AppCompatActivity() {
private val navController: NavController by lazy {
Navigation.findNavController(this, R.id.navHost)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_book)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}

91. // BookListFragment
val args = Bundle().apply {
putParcelable("book", book)
}
navController.navigate(R.id.action_list_to_details, args)
// BookDetailsFragment
val book = arguments?.getParcelable<Book>("book")
binding.book = book

92. WorkManager
• WorkManager facilita o agendamento de tarefas assíncronas e que
devem ser executadas mesmo que o aplicativo não esteja em
execução ou o dispositivo seja reiniciado.
• O agendamento pode ser único ou periódico (15 min. de intervalo)
• Uso de parâmetros de entrada e saída.
• Suporte a execuções em cadeia (chaining) (beginWith & then)
• Observar o estado do work via LiveData.
• Permite o uso de constraints (nível de bateria, tipo de rede, storage, …)
• Possui políticas de retries & backoff.

93. https://android-developers.googleblog.com/2018/10/modern-background-execution-in-android.html

94. Paging
• Carregar dados de forma paginada e sob demanda
reduz o uso da largura de banda da rede e dos
recursos do sistema.
• A Paging Library permite carregar os dados
gradualmente para listagens finitas ou “infinitas”.
• Integração com RecyclerView e LiveData

95. https://www.youtube.com/watch?v=QVMqCRs0BNA

96. #
#
🧐 #
#
#
#
🧐 #
🧐 #

97. Bonus Topics
• Organização do projeto: por pacote ou por feature?
• Injeção de Dependência: Dagger x Koin (ou Kodein)?
• Testes (JUnit, Robolectric, Espresso, MockK,
MockWebServer, …)
• Lint & KtLint
• Git Hooks
• Como está o mercado?

98. github.com/googlesamples/android-architecture

99. • Você não precisa usar tudo isso
na sua aplicação
• Na verdade, você não precisa
usar nenhum!
• O importante é saber QUANDO
USAR é QUANDO NÃO USAR
😉
• É essencial conhecer esses
tópicos, seus prós e contras e
usá-los adequadamente 💡

100. References
• Clean Architecture
https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html
• Android Architecture Components
https://developer.android.com/topic/libraries/architecture/
• LiveData beyond the ViewModel
https://medium.com/androiddevelopers/livedata-beyond-the-viewmodel-
reactive-patterns-using-transformations-and-mediatorlivedata-fda520ba00b7
• Android Architecture (Five Agency)
https://five.agency/android-architecture-part-1-every-new-beginning-is-hard/
• Joe Birch (@hitherejoe) Course at Caster.io
https://caster.io/courses/android-clean-architecture

101. Obrigado!
Nelson Glauber
@nglauber