Android Jetpack - Google IO Extended Singapore 2018

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

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

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

AndroidX
● Strict Semantic versioning rule
○ Reset to 1.0.0

Refactor to AndroidX
Migration from 28.0.0-alpha1

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

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

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"
}

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" }

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

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

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}" />

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}"
/>

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)
}

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

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

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
}
});

ViewModel + LiveData +
DataBinding = Reactive UI

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

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 = ""
)

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

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
...
}

Modern Android App
Architecture

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

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

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

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

DataSource
● PageKeyedDataSource
● ItemKeyedDataSource
● PositionalDataSource

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)
}
}

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

Navigation - Only available in Android Studio
3.2

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>

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"/>

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)

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"/>

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

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

Thank You!
Twitter : @hassanabidpk
Github : hassanabidpk

Android Jetpack - Google IO Extended Singapore 2018

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