Android Architecture Components with Kotlin

A small set of slides showing the usages and introducing the concept of the arch components library

1. Kotlin and Android Arch Components Adit Lal @aditlal
2. Introduction An application with a solid architecture should be: •Easy to scale and maintain. •Each component should be isolated and decoupled. •Easy to test Kotlin and Android Arch Components
3. Kotlin and Android Arch Components
4. Components Create an UI that automatically responds to lifecycle events. Lifecycle Kotlin and Android Arch Components
5. Components Create an UI that automatically responds to lifecycle events. Lifecycle LiveData Build data objects that notify views when underlying data changes Kotlin and Android Arch Components
6. Components Create an UI that automatically responds to lifecycle events. Lifecycle LiveData ViewModel Build data objects that notify views when underlying data changes Store UI related data that isn’t destroyed on app rotation Kotlin and Android Arch Components
7. Components Create an UI that automatically responds to lifecycle events. Lifecycle LiveData ViewModel Room Build data objects that notify views when underlying data changes Store UI related data that isn’t destroyed on app rotation Access your data with the power of SQLite and safety of in-app objects. Kotlin and Android Arch Components
8. Lifecycle States and Events Kotlin and Android Arch Components
9. Kotlin and Android Arch Components Lifecycle
10. Kotlin and Android Arch Components Lifecycle
11. Kotlin and Android Arch Components
12. Kotlin and Android Arch Components /** * Displays a message when app comes to foreground and goes to background. */ class AppLifecycleObserver @Inject constructor(context: Context) : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_START) fun onEnterForeground() { enterForegroundToast.showAfterCanceling(enterBackgroundToast) } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) fun onEnterBackground() { enterBackgroundToast.showAfterCanceling(enterForegroundToast) } } Lifecycle
13. Kotlin and Android Arch Components class AppLifecycleObserver @Inject constructor(context: Context) : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_START) fun onEnterForeground() { enterForegroundToast.showAfterCanceling(enterBackgroundToast) } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) fun onEnterBackground() { enterBackgroundToast.showAfterCanceling(enterForegroundToast) } } Lifecycle ProcessLifecycleOwner.get().lifecycle.addObserver(appLifecycleObserver)
14. Kotlin and Android Arch Components /** * Displays a message when app comes to foreground and goes to background. */ class AppLifecycleObserver @Inject constructor(context: Context) : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_START) fun onEnterForeground() { enterForegroundToast.showAfterCanceling(enterBackgroundToast) } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) fun onEnterBackground() { enterBackgroundToast.showAfterCanceling(enterForegroundToast) } } Lifecycle
15. Kotlin and Android Arch Components /** * Displays a message when app comes to foreground and goes to background. */ class AppLifecycleObserver @Inject constructor(context: Context) : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_START) fun onEnterForeground() { enterForegroundToast.showAfterCanceling(enterBackgroundToast) } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) fun onEnterBackground() { enterBackgroundToast.showAfterCanceling(enterForegroundToast) } } Lifecycle
16. LiveData LiveData is an observable data holder. It lets the components in your app, usually the UI, observe data objects for changes. Kotlin and Android Arch Components
17. Kotlin and Android Arch Components LiveData
18. Kotlin and Android Arch Components LiveData
19. Kotlin and Android Arch Components LiveData
20. LiveData var userLiveData : MutableLiveData<List<User>> = MutableLiveData();
21. LiveData var userLiveData : MutableLiveData<List<User>> = MutableLiveData(); userLiveData.value = User(id=1, name="John Doe”)
22. LiveData var userLiveData : MutableLiveData<List<User>> = MutableLiveData(); userLiveData.value = User(id=1, name="John Doe”) //Activity or fragment viewModel.getUsers().observe( this, Observer { result -> run { //Handle Result } })
23. LiveData
24. ViewModel Observes the lifecycle state of the view, maintaining consistency during configuration changes and other Android lifecycle events. The ViewModel class is designed to store and manage UI-related data so that the data survives configuration changes such as screen rotations.  Kotlin and Android Arch Components
25. ViewModel
26. ViewModel
27. class NoteViewModel @Inject constructor(var repo: NotesRepository) : ViewModel() { fun getNotes(sort: String): LiveData<List<Note>> { return repo.getAllNotes(sort = sort) } fun addNote(note: Note): LiveData<Note> { return repo.addNote(note = note) } fun deleteNote(note: Note): LiveData<Int> { return repo.deleteNote(note) } ViewModel
28. class NoteViewModel @Inject constructor(var repo: NotesRepository) : ViewModel() { fun getNotes(sort: String): LiveData<List<Note>> { return repo.getAllNotes(sort = sort) } fun addNote(note: Note): LiveData<Note> { return repo.addNote(note = note) } fun deleteNote(note: Note): LiveData<Int> { return repo.deleteNote(note) } ViewModel
29. class NoteViewModel @Inject constructor(var repo: NotesRepository) : ViewModel() { fun getNotes(sort: String): LiveData<List<Note>> { return repo.getAllNotes(sort = sort) } fun addNote(note: Note): LiveData<Note> { return repo.addNote(note = note) } fun deleteNote(note: Note): LiveData<Int> { return repo.deleteNote(note) } ViewModel
30. class NotesListActivity : AppCompatActivity(){ private lateinit var notesList: ArrayList<Note> @Inject lateinit var viewModelFactory: ViewModelFactory private val viewModel by lazy { ViewModelProviders.of( this@NotesListActivity, viewModelFactory).get(NoteViewModel::class.java) } ... } ViewModel
31. ViewModel
32. @Inject lateinit var viewModelFactory: ViewModelFactory private val viewModel by lazy { ViewModelProviders.of(this@NotesListActivity, viewModelFactory).get(NoteViewModel::class.java) } //Activity viewModel.getNotes(sort = sort).observe( this, Observer { data -> run { notesList.clear() notesList.addAll(data!!) adapter.updateItems(notesList) } }) ViewModel
33. Room Persistence library for Android Kotlin and Android Arch Components
34. Entities and Dao’s Kotlin and Android Arch Components Room
35. @Entity(tableName = "user_table") data class User(var created: Date = Date(), var name: String = "", @PrimaryKey var id: Int = 0) Entities
36. interface BaseDao<T> { @Insert fun insert(vararg obj: T) } @Dao abstract class DataDao : BaseDao<Data>() { @Query("SELECT * FROM Data") abstract fun getData(): List<Data> } Dao
37. @Dao interface UserDao { @Insert(onConflict = OnConflictStrategy.REPLACE) fun insert(user: User) @Delete fun delete(user: User) @Query("SELECT * FROM user_table") fun getUsers(): List<User> } Dao
38. @Dao interface UserDao { @Insert(onConflict = OnConflictStrategy.REPLACE) fun insert(user: User) @Delete fun delete(user: User) @Query("SELECT * FROM user_table") fun getUsers(): List<User> } Dao
39. @Dao interface UserDao { @Insert(onConflict = OnConflictStrategy.REPLACE) fun insert(user: User) @Delete fun delete(user: User) @Query("SELECT * FROM user_table") fun getUsers(): LiveData<List<User>> } Dao
40. @Transaction open fun updateData(users: List<User>) { deleteAllUsers() insertAll(users) } Dao
41. class UserAndAllPets { @Embedded var user: User? = null @Relation(parentColumn = “userId”, entityColumn = “owner”) var pets: List<Pet> = ArrayList() } //UserDao.kt @Transaction @Query(“SELECT * FROM Users”) List<UserAndAllPets> getUsers(); Dao
42. @Database(entities = arrayOf(User::class), version = 1, exportSchema = true) @TypeConverters(Converters::class) abstract class AppDatabase : RoomDatabase() { abstract fun UserDao(): UserDao } Database
43. class MyApp : Application() { lateinit var mDataBase: AppDatabase override fun onCreate() { super.onCreate() mDataBase = Room.databaseBuilder(this, AppDatabase::class.java, "users").build() } } Database
44. @Provides @Singleton fun provideDB(context: Context): AppDatabase = Room.databaseBuilder(context, AppDatabase::class.java, “users") .fallbackToDestructiveMigration() .build() Database
45. Paging Efficient Lists and data loading Kotlin and Android Arch Components
46. Paging
47. Paging
48. class MyPagedListAdapter(diffCallback: DiffCallback<User>) : PagedListAdapter<User, MyPagedListAdapter.ViewHolder>(diffCallback) { PagedListAdapter override fun onBindViewHolder(holder: MyPagedListAdapter.ViewHolder?, position: Int) { getItem(position)?.let { holder?.setData(it) } } override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): MyPagedListAdapter.ViewHolder { val view = LayoutInflater.from(parent?.context).inflate(R.layout.item_user, parent, false) return ViewHolder(view) } }
49. class MyPagedListAdapter(diffCallback: DiffCallback<User>) : PagedListAdapter<User, MyPagedListAdapter.ViewHolder>(diffCallback) { PagedListAdapter override fun onBindViewHolder(holder: MyPagedListAdapter.ViewHolder?, position: Int) { getItem(position)?.let { holder?.setData(it) } } override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): MyPagedListAdapter.ViewHolder { val view = LayoutInflater.from(parent?.context).inflate(R.layout.item_user, parent, false) return ViewHolder(view) } }
50. class MyPagedListAdapter(diffCallback: DiffCallback<User>) : PagedListAdapter<User, MyPagedListAdapter.ViewHolder>(diffCallback) { PagedListAdapter override fun onBindViewHolder(holder: MyPagedListAdapter.ViewHolder?, position: Int) { getItem(position)?.let { holder?.setData(it) } } override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): MyPagedListAdapter.ViewHolder { val view = LayoutInflater.from(parent?.context).inflate(R.layout.item_user, parent, false) return ViewHolder(view) } }
51. DiffCallback private val diffCallback = object : DiffUtil.ItemCallback<User>() { override fun areItemsTheSame(oldItem: User, newItem: User): Boolean = oldItem.id == newItem.id override fun areContentsTheSame(oldItem: User, newItem: User): Boolean = oldItem == newItem } }
52. Query @Query("SELECT * FROM users ORDER WHERE age>:age ORDER by name DESC, id ASC") abstract fun usersOlderThan(age: Int): LivePagedListProvider<Int, User>
53. ViewModel class UserViewModel(val db:AppDB) : ViewModel() { val users: LiveData<PagedList<User>> fun getUsersOlderThan(age) { users = db.userDao().usersOlderThan(age) .create(0, PagedList.Config.Builder() .setPageSize(20) .setPrefetchDistance(20) .setEnablePlaceholders(false) .build()) } }
54. Activity viewModel.getUsersOlderThan(5).observe(this, pagedList -> { usersAdapter.setList(pagedList); });
55. Thank you Questions Kotlin and Android Arch Components @aditlal