Un recorrido por las distintas soluciones para trabajar cuando no hay conexion y sincronizar datos que hemos implementado, no solo para lidiar con la falta de conectividad sino tambien con la mala conectividad. Desde utilizar Receivers hasta Work Manager, analizando el porque necesitamos este tipo de soluciones para mejorar nuestras apps.

1. HOW DO WE WORK
OFFLINE
JUAN CARLOS GARCÍA SECO

2. ▸ Android Developer
▸ jcgseco@gmail.com
▸ @ikarimeister

3. USE CASE

4. ACCESS
CONTROL

5. TICKET SALES
ON BOARD

6. WHY OFFLINE?

7. TUNNELS

8. REMOTE PLACES

9. GOOD SIGNAL
HIGH SPEED

10. NO CONNECTION

11. GOING OFFLINE

12. BACKEND AS SOURCE
OF TRUTH

13. PERSISTING OFFLINE
REQUESTS

14. sealed class NetworkError : Errors()
data class NoInternetConnection(
val request: String,
val type: OfflineRequestType
) : Errors()
object AlreadyCreated : NetworkError()
object BadRequest : NetworkError()
object Forbidden : NetworkError()

15. suspend fun createSell(sale : SaleRequestDto)
: Either<NetworkError, SaleResponseDto>
apiClient.createSell(sale)
.mapLeft { it.mapToDomainError() }

16. fun NetworkError.mapToDomainError(): DomainError =
when (this) {
is NoInternetConnection -> {
repository?.save(this.request,
this.type)
DomainError
}
AlreadyCreated -> DomainError
BadRequest -> DomainError
Forbidden -> DomainError
}

17. INITIAL DATA LOAD

18. WE NEED SOME DATA
TO WORK

19. BE AWARE IF YOU NEED THE
DATA FOR YOUR FEATURE

20. DON’T BURN THE
BACKEND

21. SYNCHRONIZING

22. ON DEMAND SYNC

23. PERIODIC SYNC

24. fun initSync() {
val myIntent = Intent(this,
SyncService::class.java)
val pendingIntent =
PendingIntent.getService(this, 0, myIntent, 0)
getSystemService(Context.ALARM_SERVICE)
.setRepeating(
AlarmManager.RTC_WAKEUP, 0,
frequency, pendingIntent)
}

25. class SyncService : IntentService(SyncService::class.java.name) {
lateinit var repository : OfflineRepository
lateinit var salesSync : SalesSyncUseCase
lateinit var accessSync : AccessControlSyncUseCase
lateinit var refundSync : RefundSyncUseCase
override fun onHandleIntent(intent: Intent) {
if (hasConnection()) {
repository.getAll().map{ offlineRequest ->
when(offlineRequest.type){
OfflineRequestType.SALES ->
salesSync(offlineRequest.request)
OfflineRequestType.REFUND -> refundSync(offlineRequest.request)
OfflineRequestType.ACCESS_CONTROL -> accessSync(offlineRequest.request)
}
}
}
}
}

26. IMPROVING UX

27. OFFLINE MODE

28. i
apiClient.createSell(sale)
.mapLeft { it.mapToDomainError() }

29. LOCAL STORAGE AS
SOURCE OF TRUTH

30. REMOVING
PROGRESS BAR

31. OPTIMISTIC
FEEDBACK

32. JETPACK TO RESCUE

33. WORK MANAGER

34. class RemoveLocalCopy(
context: Context,
params: WorkerParameters
) : Worker(context, params) {
private val use case = UseCase()
override fun doWork(): Result =
usecase(inputData.keyValueMap[PARAM] as String).fold(
{
when (it) {
IOError -> Result.retry()
ForbiddenOperationError, FatalError, ResourceNotFound -> Result.failure()
}
},
{
Result.success(workDataOf(PARAM to it))
}
)
}

35. CONSTRAINTS &
BACKOFF POLICIES

36. fun OneTimeWorkRequest.Builder.requireInternetWork(data:
Data, retry: Long)
: OneTimeWorkRequest =
this.setConstraints(
Constraints.Builder()
.setRequiredNetworkType(NetworkType.CONNECTED)
.build()
)
.setBackoffCriteria(BackoffPolicy.LINEAR, retry,
TimeUnit.SECONDS)
.setInputData(data)
.build()

37. UNIQUE WORKS &
EXISTING POLICIES

38. val work: WorkContinuation =
WorkManager.getInstance()
.beginUniqueWork(uniqueName,
ExistingWorkPolicy.KEEP, request1)
.then(request2)
.then(request3)
.then(listOf(request4, request5))
work.enqueue()

39. NEXT STEPS

40. PERIODIC SYNC TO
WORKERS

41. OPTIMIZE DATA
LOADS

42. THANKS!
ANY QUESTIONS?
You can find me at:
▸jcgseco@gmail.com
▸@ikarimeister

43. CREDITS AND RESOURCES
▸ Saúl Díaz: Offline Second
▸ Android Dev Podcast: Offline First
▸ Android Dev Podcast: Workers & Room
▸ Android Developers: https://developer.android.com/topic/
libraries/architecture/workmanager
▸ Working with WorkManager (Android Dev Summit ’18):
https://www.youtube.com/watch?v=83a4rYXsDs0

44. IMAGES
▸ Barrier Photo: https://www.flickr.com/photos/48603151@N00/
▸ Box-Office Photos: https://www.flickr.com/photos/incinema/
▸ Train Photos: https://www.flickr.com/photos/jtcurses9/
▸ Vader Photo: https://www.flickr.com/photos/jdhancock/
▸ Offline Photo: https://www.flickr.com/photos/no-luogo/