Android Architecture Components with Kotlin

Kotlin and Android Arch Components Adit Lal @aditlal

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

Kotlin and Android Arch Components

Components Create an UI that automatically responds to lifecycle events. Lifecycle Kotlin and Android Arch Components

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

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

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

Lifecycle States and Events Kotlin and Android Arch Components

Kotlin and Android Arch Components Lifecycle

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

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)

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

Kotlin and Android Arch Components LiveData

LiveData var userLiveData : MutableLiveData<List<User>> = MutableLiveData();

LiveData var userLiveData : MutableLiveData<List<User>> = MutableLiveData(); userLiveData.value = User(id=1, name="John Doe”)

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 } })

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

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

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

@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

Room Persistence library for Android Kotlin and Android Arch Components

Entities and Dao’s Kotlin and Android Arch Components Room

@Entity(tableName = "user_table") data class User(var created: Date = Date(), var name: String = "", @PrimaryKey var id: Int = 0) Entities

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

@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

@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

@Transaction open fun updateData(users: List<User>) { deleteAllUsers() insertAll(users) } Dao

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

@Database(entities = arrayOf(User::class), version = 1, exportSchema = true) @TypeConverters(Converters::class) abstract class AppDatabase : RoomDatabase() { abstract fun UserDao(): UserDao } Database

class MyApp : Application() { lateinit var mDataBase: AppDatabase override fun onCreate() { super.onCreate() mDataBase = Room.databaseBuilder(this, AppDatabase::class.java, "users").build() } } Database

@Provides @Singleton fun provideDB(context: Context): AppDatabase = Room.databaseBuilder(context, AppDatabase::class.java, “users") .fallbackToDestructiveMigration() .build() Database

Paging Efficient Lists and data loading Kotlin and Android Arch Components

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) } }

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 } }

Query @Query("SELECT * FROM users ORDER WHERE age>:age ORDER by name DESC, id ASC") abstract fun usersOlderThan(age: Int): LivePagedListProvider<Int, User>

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()) } }

Activity viewModel.getUsersOlderThan(5).observe(this, pagedList -> { usersAdapter.setList(pagedList); });

Thank you Questions Kotlin and Android Arch Components @aditlal

Android Architecture Components with Kotlin

More Related Content

What's hot

Similar to Android Architecture Components with Kotlin

Recently uploaded

Android Architecture Components with Kotlin