In this talk, I covered Android Jetpack's architecture components. They provide you a new way to architect your app in modern style. As Google and Android community considers Kotlin as first class citizen in Android developement, therefore almost all new code samples are provided in Kotlin.

1. Android Jetpack
Hassan Abid - Google Developer Expert Android
Presented at Google IO Extended Singapore 2018

3. Google I/O Talks
● Android Jetpack: what's new in Android Support Library
● Android Jetpack: what's new in Architecture Components
● Modern Android development: Android Jetpack, Kotlin, and more
● Android Jetpack: how to smartly use Fragments in your UI
● Android Jetpack: manage UI navigation with Navigation Controller
● Android Jetpack: manage infinite lists with RecyclerView and Paging
● Android Jetpack: easy background processing with WorkManager
● Android Slices: build interactive results for Google Search
● Android Jetpack: sweetening Kotlin development with Android KTX
● Protips: a fresh look at advanced topics for Android experts

4. AndroidX
AndroidX: "Android Extension Libraries"
android.support.v4.view.ViewCompat
→ androidx.core.view.ViewCompat
android.support.v7.app.AppCompatActivity
→ androidx.appcompat.app.AppCompatActivity
android.arch.persistence.room.RoomDatabase
→ androidx.room.RoomDatabase

5. AndroidX
● Strict Semantic versioning rule
○ Reset to 1.0.0

6. Refactor to AndroidX
Migration from 28.0.0-alpha1

7. Recommended Architecture

8. Architecture Components
● LifeCycle (1.1.1 Stable)
● Databinding (Stable)
● ViewModel (Stable)
● LiveData (Stable)
● Room (1.1.1 Stable)
● Paging (1.0.1 Stable)
● WorkManager (Alpha Release)
● Navigation (Alpha Release)
https://developer.android.com/jetpack/docs/release-notes

9. Adding Components to your project
allprojects {
repositories {
jcenter()
google()
}
}

10. Example : LifeCycle
dependencies {
def lifecycle_version = "1.1.1"
// ViewModel and LiveData
implementation "android.arch.lifecycle:extensions:$lifecycle_version"
// alternatively - just ViewModel. use -ktx for Kotlin
implementation "android.arch.lifecycle:viewmodel:$lifecycle_version"
}

11. Example : LifeCycle (Android X)
dependencies {
def lifecycle_version = "2.0.0-alpha1"
// ViewModel and LiveData
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
// alternatively - just ViewModel use -ktx for Kotlin
implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version" }

12. LifeCycle

13. LifeCycle

14. LifeCycle Benefits
● Avoid Lifecycle related UI state loss: View Model
● Observability for your UI: LiveData
● Avoid Lifecycle related memory leak
● LiveData transformations
● UI-Database observations : LiveData /Room
● XML-ViewModel observations: DataBinding
● Query and Observe UI Lifecycle State

15. Fragment View Lifecycle
viewModel.plantAndGardenPlantings.observe(viewLifecycleOwner, Observer { result ->
if (result != null && result.isNotEmpty())
adapter.submitList(result)
})

16. Databinding

17. Databinding
A support library that allows you to bind UI components in your
layouts to data sources in your app using a declarative format rather
than programmatically.
TextView textView = findViewById(R.id.sample_text);
textView.setText(viewModel.getUserName());
<TextView
android:text="@{viewmodel.userName}" />

18. Databinding LiveData
class PlantDetailViewModel() : ViewModel() {
val plant: LiveData<Plant> = ...
}
<data>
<variable
name="viewModel"
type="viewmodels.PlantAndGardenPlantingsViewModel"/>
</data>
<ImageView
android:layout_width="match_parent"
android:layout_height="100dp"
android:scaleType="centerCrop"
app:imageFromUrl="@{viewModel.imageUrl}"
/>

19. Databinding : One More thing
android {
dataBinding {
enabled = true
}
}
val binding = DataBindingUtil.inflate<FragmentPlantDetailBinding>(
inflater, R.layout.fragment_plant_detail, container,
false).apply {
viewModel = plantDetailViewModel
setLifecycleOwner(this@PlantDetailFragment)
}

20. ViewModel

21. ViewModel
● Provide data for UI Components
● Survive Configuration changes
ViewModel
Hold UI Data
Repository
API for loading and saving
data
Activity
Drawing UI
User Interactions
Presenter
Process Data for UI

22. ViewModel
class PlantDetailViewModel() : ViewModel() {
val plant: LiveData<Plant>
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val plantDetailViewModel = ViewModelProviders.of(this, factory)
.get(PlantDetailViewModel::class.java)
}
Don’t store activity context in
ViewModel

23. LiveData

24. LiveData
LiveData is an observable data holder. It is lifecycle aware
public class ProductViewModel extends AndroidViewModel {
private final LiveData<ProductEntity> mObservableProduct;
// ....
public LiveData<ProductEntity> getObservableProduct() {
return mObservableProduct;
}
}
// Observe product data and
model.getObservableProduct().observe(this, new Observer<ProductEntity>() {
@Override
public void onChanged(@Nullable ProductEntity productEntity) {
// update UI
}
});

25. ViewModel + LiveData +
DataBinding = Reactive UI

26. Room

27. Room
● Object Mapping for SQLite Database
● Raw Queries are supported
● Support for RxJava
● Work with java.util.Optional

28. Room - Entity
@Entity(tableName = "plants")
data class Plant(
@PrimaryKey @ColumnInfo(name = "id") val plantId: String,
val name: String,
val description: String,
val growZoneNumber: Int,
val wateringInterval: Int = 7,
val imageUrl: String = ""
)

29. Room - Dao
@Dao
interface PlantDao {
@Query("SELECT * FROM plants ORDER BY name")
fun getPlants(): LiveData<List<Plant>>
@Query("SELECT * FROM plants WHERE growZoneNumber = :growZoneNumber ORDER BY
name")
fun getPlantsWithGrowZoneNumber(growZoneNumber: Int): LiveData<List<Plant>>
@Query("SELECT * FROM plants WHERE id = :plantId")
fun getPlant(plantId: String): LiveData<Plant>
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insertAll(plants: List<Plant>)
}
Observable queries

30. Room - RoomDatabase
@Database(entities = [GardenPlanting::class, Plant::class], version = 1,
exportSchema = false)
@TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
abstract fun gardenPlantingDao(): GardenPlantingDao
abstract fun plantDao(): PlantDao
...
}

31. Modern Android App
Architecture

33. Paging Library

34. Paging
● Fetch from database, Network, or both into RecycleView
● Extension of observable List Pattern (e.g LiveData<List>)
● Configurable Load Size, prefetch, placeholders
● Integrates with Room, LiveData, RX
● Stable release

35. Paging - core components 1/2
● PagedList
○ Load data in pages
○ Async data loading
● DataSource and DataSource.Factory
○ Base class for loading snapshots of data into PagedList
○ Backed by Network or Database

36. Paging - core components 2/2
● LivePagedListBuilder
○ Build a LiveData<PagedList> based on DataSource.Factory and a
PagedList.config
● BoundaryCallBack
○ Signals when PagedList has reached end of available data
● PagedListAdapter
○ A RecyclerView.Adapter that presents data from PagedLists

37. Paging - simplified
UI
PageListAdapter
PagedList
--------------
--------------
--------------
Data Layer
DataSource.Factory
BoundyCallBack
Data Source
OnItemAtEndLoaded()
Save data
Get Data
ViewModel
LiveData<PagedList>
Repository
LivePagedListBuilder
LiveData<PagedList>
create()
Build
--------------
Load
more

38. DataSource
● PageKeyedDataSource
● ItemKeyedDataSource
● PositionalDataSource

39. BoundaryCallBack
class ConcertBoundaryCallback(
private val query: String,
private val service: MyService,
private val cache: MyLocalCache
) : PagedList.BoundaryCallback<Concert>() {
override fun onZeroItemsLoaded() {
requestAndSaveData(query)
}
override fun onItemAtEndLoaded(itemAtEnd: Concert) {
requestAndSaveData(query)
}
}

40. Navigation

41. Navigation - Challenges
● Passing Arguments
● Deep Links
● Fragment Transactions
● Testing

42. Navigation - Only available in Android Studio
3.2

43. Navigation
<navigation xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
app:startDestination="@+id/garden_fragment">
<fragment
android:id="@+id/plant_list_fragment"
android:name="com.google.samples.apps.sunflower.PlantListFragment">
<argument
.../>
<action
android:id="@+id/action_plant_list_fragment_to_plant_detail_fragment"
app:destination="@id/plant_detail_fragment"
app:enterAnim="@anim/slide_in_right"
app:exitAnim="@anim/slide_out_left"
app:popEnterAnim="@anim/slide_in_left"
app:popExitAnim="@anim/slide_out_right" />
</fragment>
....
</navigation>

44. Navigation - Add Navgraph
<fragment
android:id="@+id/garden_nav_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_garden"/>

45. Navigation - NavigationController
val navController = Navigation.findNavController(this,
R.id.garden_nav_fragment)
// Set up ActionBar
setSupportActionBar(binding.toolbar)
NavigationUI.setupActionBarWithNavController(this,
navController, drawerLayout)
// Set up navigation menu
binding.navigationView.setupWithNavController(navController)

46. Navigation - NavigationOnClickListener
private fun createOnClickListener(plantId: String): View.OnClickListener {
val bundle = bundleOf(PlantDetailFragment.ARG_ITEM_ID to plantId)
return Navigation.createNavigateOnClickListener(
R.id.action_plant_list_fragment_to_plant_detail_fragment, bundle)
}
<action
android:id="@+id/action_plant_list_fragment_to_plant_detail_fragment"
app:destination="@id/plant_detail_fragment"/>

47. Samples and Code Lab
Android SunFlower https://github.com/googlesamples/android-sunflower
Universal Music Player
https://github.com/googlesamples/android-UniversalMusicPlayer/blob/master/app/build.gradle
Architecture Components https://github.com/googlesamples/android-architecture-components
Code Labs https://codelabs.developers.google.com/?cat=Android
Guide to Architecture Components https://developer.android.com/jetpack/docs/guide

48. Conclusion
● Finally Android platform got an Architecture
● Highly Recommended for New Apps
● Try out samples and codelabs

49. Thank You!
Twitter : @hassanabidpk
Github : hassanabidpk