Firebase & Jetpack: fit like a glove (360|AnDev, Denver)

1.

Firebase & Jetpack: fit like a glove Doug Stevenson @CodingDoug
Get the code: Get the app: bit.ly/2NtAuQP bit.ly/2NtGedo

2.

@CodingDoug @CodingDoug

3.

@CodingDoug @CodingDoug Cloud hosted, realtime, NoSQL

4.


5.

@CodingDoug A simple example … or is it? val firestore
= FirebaseFirestore.getInstance() val ref = firestore.collection("coll").document("id") ref.get() .addOnSuccessListener { snapshot -> // We have data! Now what? } .addOnFailureListener { exception -> // Oh, snap } How should I do async programming? Do I directly update my views here? What manages this singleton?

6.

@CodingDoug <TextView/> <Button/> Your Arch WW D?

7.

@CodingDoug Data Binding Lifecycles LiveData Navigation Paging Room ViewModel WorkManager

8.

@CodingDoug LiveData ViewModel Notify views when underlying database changes Manage
UI-related data in a lifecycle-conscious way

9.


10.


11.


12.


13.

@CodingDoug Handle stock price changes from a document in Firestore

14.

val firestore = FirebaseFirestore.getInstance()

15.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK")

16.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK") ref.addSnapshotListener { snapshot, exception -> if (snapshot != null) { } else if (exception != null) { } }

17.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK") ref.addSnapshotListener { snapshot, exception -> if (snapshot != null) { val model = StockPrice( ticker = snapshot.id, price = snapshot.getDouble("price")!!.toFloat() ) } else if (exception != null) { } }

18.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK") ref.addSnapshotListener { snapshot, exception -> if (snapshot != null) { val model = StockPrice( ticker = snapshot.id, price = snapshot.getDouble("price")!!.toFloat() ) } else if (exception != null) { TODO("This is just a simple code sample, ain't got time for this.") } }

19.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK") ref.addSnapshotListener { snapshot, exception -> if (snapshot != null) { val model = StockPrice( ticker = snapshot.id, price = snapshot.getDouble("price")!!.toFloat() ) someTextView.text = model.ticker } else if (exception != null) { TODO("This is just a simple code sample, ain't got time for this.") } }

20.

val firestore = FirebaseFirestore.getInstance() val ref = firestore.collection("stocks-live").document("HSTK") ref.addSnapshotListener { snapshot, exception -> if (snapshot != null) { val model = StockPrice( ticker = snapshot.id, price = snapshot.getDouble("price")!!.toFloat() ) someTextView.text = model.ticker throw PoorArchitectureException("let's rethink mixing data store and views”) } else if (exception != null) { TODO("This is just a simple code sample, ain't got time for this.") } }

21.

@CodingDoug <TextView/> LiveData

22.

@CodingDoug @CodingDoug LiveData Observable Code can register observers to receive
updates. Genericized Subclasses must specify a type of object containing updates. Lifecycle-aware Handles component start, stop, and destroy states automatically.

23.

@CodingDoug Keep views up to date with LiveData class MyActivity
: AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.stuff) val tickerTextView = findViewById<TextView>(R.id.tv_ticker) val priceTextView = findViewById<TextView>(R.id.tv_price) } }

24.

: AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.stuff) val tickerTextView = findViewById<TextView>(R.id.tv_ticker) val priceTextView = findViewById<TextView>(R.id.tv_price) val liveData: LiveData<StockPrice> = getLiveDataForMyTicker("HSTK") } }

25.

: AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.stuff) val tickerTextView = findViewById<TextView>(R.id.tv_ticker) val priceTextView = findViewById<TextView>(R.id.tv_price) val liveData: LiveData<StockPrice> = getLiveDataForMyTicker("HSTK") liveData.observe(this@MyActivity, Observer<StockPrice> { stockPrice -> }) } }

26.

: AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.stuff) val tickerTextView = findViewById<TextView>(R.id.tv_ticker) val priceTextView = findViewById<TextView>(R.id.tv_price) val liveData: LiveData<StockPrice> = getLiveDataForMyTicker("HSTK") liveData.observe(this@MyActivity, Observer<StockPrice> { stockPrice -> if (stockPrice != null) { tickerTextView.text = stockPrice.ticker priceTextView.text = stockPrice.price.toString() } }) } }

27.

@CodingDoug LiveData is aware of the Android Activity lifecycle

28.

@CodingDoug LiveData is aware of the Android Activity lifecycle override
fun onStop() { super.onStop() // LivaData becomes inactive, doesn't notify observers }

29.

fun onStop() { super.onStop() // LivaData becomes inactive, doesn't notify observers } override fun onStart() { super.onStart() // LivaData becomes active again, notifies observers with latest data }

30.

fun onStop() { super.onStop() // LivaData becomes inactive, doesn't notify observers } override fun onStart() { super.onStart() // LivaData becomes active again, notifies observers with latest data } override fun onDestroy() { super.onDestroy() // LiveData removes all activity-scoped observers - no leaks! }

31.

@CodingDoug Implement LiveData with Firestore document updates class StockPriceLiveData() {
}

32.

@CodingDoug Implement LiveData with Firestore document updates class StockPriceLiveData() :
LiveData<StockPrice>() { }

33.

@CodingDoug Implement LiveData with Firestore document updates class StockPriceLiveData(private val
documentReference: DocumentReference) : LiveData<StockPrice>() { }

34.

documentReference: DocumentReference) : LiveData<StockPrice>() { override fun onActive() { // # observers 0 -> 1 woo-hoo! someone cares! } }

35.

documentReference: DocumentReference) : LiveData<StockPrice>() { private var listenerRegistration: ListenerRegistration? = null override fun onActive() { // # observers 0 -> 1 woo-hoo! someone cares! listenerRegistration = documentReference.addSnapshotListener(....) } }

36.

documentReference: DocumentReference) : LiveData<StockPrice>() { private var listenerRegistration: ListenerRegistration? = null override fun onActive() { // # observers 0 -> 1 woo-hoo! someone cares! listenerRegistration = documentReference.addSnapshotListener(....) } override fun onInactive() { // # observers 1 -> 0 awww, everyone left... } }

37.

documentReference: DocumentReference) : LiveData<StockPrice>() { private var listenerRegistration: ListenerRegistration? = null override fun onActive() { // # observers 0 -> 1 woo-hoo! someone cares! listenerRegistration = documentReference.addSnapshotListener(....) } override fun onInactive() { // # observers 1 -> 0 awww, everyone left... listenerRegistration!!.remove() } }

38.

documentReference: DocumentReference) : LiveData<StockPrice>(), EventListener<DocumentSnapshot> { private var listenerRegistration: ListenerRegistration? = null override fun onActive() { // # observers 0 -> 1 woo-hoo! someone cares! listenerRegistration = documentReference.addSnapshotListener(this) } override fun onInactive() { // # observers 1 -> 0 awww, everyone left... listenerRegistration!!.remove() } override fun onEvent(snap: DocumentSnapshot?, e: FirebaseFirestoreException?) {} }

39.

@CodingDoug Implement LiveData with Firestore document updates override fun onEvent(snap:
DocumentSnapshot?, e: FirebaseFirestoreException?) { }

40.

DocumentSnapshot?, e: FirebaseFirestoreException?) { if (snap != null && snap.exists()) { val model = StockPrice( snap.id, snap.getDouble("price")!!.toFloat() ) } }

41.

DocumentSnapshot?, e: FirebaseFirestoreException?) { if (snap != null && snap.exists()) { val model = StockPrice( snap.id, snap.getDouble("price")!!.toFloat() ) // Here you go, all my admiring observers! Go update your UI! setValue(model) } }

42.

DocumentSnapshot?, e: FirebaseFirestoreException?) { if (snap != null && snap.exists()) { val model = StockPrice( snap.id, snap.getDouble("price")!!.toFloat() ) // Here you go, all my admiring observers! Go update your UI! setValue(model) } else if (e != null) { TODO("You should handle errors. Do as I say, not as I do.") } }

43.

@CodingDoug • Who creates the instance of LiveData? ◦ StockPriceLiveData
constructor exposes Firestore implementation details. ◦ Remember: views should know nothing of data store. • LiveData loses its data on configuration change. ◦ Would rather have immediate LiveData results after configuration change. Two problems to resolve

44.

@CodingDoug @CodingDoug ViewModel Survives configuration changes Same ViewModel instance appears
in reconfigured activities Shared & Managed System manages the scope of instances, may be shared Lifecycle-aware Automatically cleaned up on final destroy

45.

@CodingDoug ViewModel

46.

@CodingDoug Implement a ViewModel that yields a LiveData class StocksViewModel
: ViewModel() { }

47.

: ViewModel() { fun getStockPriceLiveData(ticker: String): StockPriceLiveData { } }

48.

: ViewModel() { // Find a repository object using dependency injection private val repository: StockDataRepository = ... fun getStockPriceLiveData(ticker: String): StockPriceLiveData { } }

49.

: ViewModel() { // Find a repository object using dependency injection private val repository: StockDataRepository = ... fun getStockPriceLiveData(ticker: String): StockPriceLiveData { } } // StockDataRepository knows where the data actually comes from interface StockDataRepository { fun getStockPriceLiveData(ticker: String): StockPriceLiveData }

50.

: ViewModel() { // Find a repository object using dependency injection private val repository: StockDataRepository = ... fun getStockPriceLiveData(ticker: String): StockPriceLiveData { return repository.getStockPriceLiveData(ticker) } } // StockDataRepository knows where the data actually comes from interface StockDataRepository { fun getStockPriceLiveData(ticker: String): StockPriceLiveData }

51.

@CodingDoug Implement a repository backed by Firestore interface StockDataRepository {
fun getStockPriceLiveData(ticker: String): StockPriceLiveData }

52.

fun getStockPriceLiveData(ticker: String): StockPriceLiveData } class FirestoreStockDataRepository : StockDataRepository { override fun getStockPriceLiveData(ticker: String): StockPriceLiveData { } }

53.

fun getStockPriceLiveData(ticker: String): StockPriceLiveData } class FirestoreStockDataRepository : StockDataRepository { // Should use DI for this too private val firestore = FirebaseFirestore.getInstance() override fun getStockPriceLiveData(ticker: String): StockPriceLiveData { } }

54.

fun getStockPriceLiveData(ticker: String): StockPriceLiveData } class FirestoreStockDataRepository : StockDataRepository { // Should use DI for this too private val firestore = FirebaseFirestore.getInstance() override fun getStockPriceLiveData(ticker: String): StockPriceLiveData { val ref = firestore.collection("stocks-live").document(ticker) return StockPriceLiveData(ref) } }

55.

@CodingDoug LiveData & ViewModel & Repository & Firebase

56.

@CodingDoug Use ViewModel and LiveData in an activity class MyActivity
: AppCompatActivity() { private lateinit var tickerTextView: TextView private lateinit var priceTextView: TextView override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // Redacted: inflate and initialize views... } }

57.

: AppCompatActivity() { private lateinit var tickerTextView: TextView private lateinit var priceTextView: TextView override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // Inflate and initialize views... val viewModel = ViewModelProviders.of(this).get(StocksViewModel::class.java) } }

58.

: AppCompatActivity() { private lateinit var tickerTextView: TextView private lateinit var priceTextView: TextView override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // Inflate and initialize views... val viewModel = ViewModelProviders.of(this).get(StocksViewModel::class.java) val liveData = viewModel.getStockPriceLiveData("HSTK") } }

59.

: AppCompatActivity() { private lateinit var tickerTextView: TextView private lateinit var priceTextView: TextView override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // Inflate and initialize views... val viewModel = ViewModelProviders.of(this).get(StocksViewModel::class.java) val liveData = viewModel.getStockPriceLiveData("HSTK") liveData.observe(this, Observer<StockPrice> { stockPrice -> }) } }

60.

: AppCompatActivity() { private lateinit var tickerTextView: TextView private lateinit var priceTextView: TextView override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // Inflate and initialize views... val viewModel = ViewModelProviders.of(this).get(StocksViewModel::class.java) val liveData = viewModel.getStockPriceLiveData("HSTK") liveData.observe(this, Observer<StockPrice> { stockPrice -> if (stockPrice != null) { tickerTextView.text = stockPrice.ticker priceTextView.text = stockPrice.price.toString() } }) } }

61.

@CodingDoug

62.

@CodingDoug • LiveData<StockPrice> doesn’t propagate errors • Errors need to
bubble up to the UI   class DataOrException<T, E: Exception?>(val data: T?, val exception: E?) typealias StockPriceOrException = DataOrException<StockPrice, Exception> LiveData<StockPrice> => LiveData<StockPriceOrException> What about errors?

63.

@CodingDoug • https://github.com/CodingDoug/firebase-jetpack • Sync individual documents/nodes, and queries ◦
Query → RecyclerView support is inefficient and still needs work • Implementations for both Realtime Database and Firestore • Background sync with WorkManager • Backend implemented with TypeScript for node and Cloud Functions • Stay tuned for more! Lots more in the repo

64.

Thank you! @CodingDoug firebase.google.com Get the code: Get the app:
bit.ly/2NtAuQP bit.ly/2NtGedo

Firebase & Jetpack: fit like a glove (360|AnDev, Denver)

Firebase & Jetpack: fit like a glove (360|AnDev, Denver)

Want more?

Transcript