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Workout your tasks
with WorkManager
Magda Miu @magdamiu
Squad Lead Developer at Orange
Android Google Developer Expert
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A User’s Nightmare...
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A User’s Nightmare...
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A User’s Nightmare...
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53%
Users who uninstalled a mobile app with crashes, freezes or errors
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Users who stopped to use a mobile app due to heavy battery usage
36%
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1
4
3
2
Agenda
Android Memory Model
Background Processing Solutions
WorkManager
Summary
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1
4
3
2
Agenda
Android Memory Model
Background Processing Solutions
WorkManager
Summary
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Android is for everyone
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Android is for everyone
apps
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Android is for everyone
apps devices
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Android is for everyone
apps devices users
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Android is for everyone
apps devices users
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Android is for everyone
apps devices users
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Physical memory on device
Used pages
Memory actively being used
Cached pages
Memory backed by device storage. Can be reclaimed if needed.
Free pages
Memory not currently being used for anything.
Source: Understanding Android memory usage (Google I/O '18)
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memory free
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memory free page reclaim
(kswapd)
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memory free page reclaim
(kswapd)
low memory
killer (lmk)
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
Source: Understanding Android memory usage (Google I/O '18)
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android process list
Native Init kswapd netd logd adb ...
System system_server
Persistent
Foreground
Perceptible
Service
Home
Previous
Cached
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Android battery optimizations
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Android battery optimizations
Doze mode
App standby
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Android battery optimizations
Doze mode
App standby
Doze on the go
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Android battery optimizations
Doze mode
App standby
Doze on the go Background service
limitations
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Android battery optimizations
Doze mode
App standby
Doze on the go Background service
limitations
App standby
buckets
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1
4
3
2
Agenda
Android Memory Model
Background Processing Solutions
WorkManager
Summary
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Exact
Timing
Deferrable
Guaranteed
Execution
Best-Effort
Credit: Android Jetpack: easy background processing with WorkManager (Google I/O '18)
time/importance
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Exact
Timing
Deferrable
Guaranteed
Execution
Best-Effort
ThreadPool
Coroutines
RxJava
ThreadPool
Coroutines
RxJava
JobScheduler
JobDispatcher
AlarmManager
BroadcastReceivers
Foreground
Service
time/importance
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Exact
Timing
Deferrable
Guaranteed
Execution
Best-Effort
ThreadPool
Coroutines
RxJava
ThreadPool
Coroutines
RxJava
JobScheduler
JobDispatcher
AlarmManager
BroadcastReceivers
WorkManager
Foreground
Service
time/importance
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4
3
Agenda
WorkManager
Summary
1
2
Android Memory Model
Background Processing Solutions
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“WorkManager is a library for managing
deferrable and guaranteed background
work.”
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Why to use WorkManager?
● Backward compatibility with different OS versions (API level 14+)
● Follows system health best practices
● Supports one-off and periodic tasks
● Supports chained tasks with input/output
● Defines constraints on when the task runs
● Guarantees task execution, even if the app or device restarts
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Fetching data periodically
Uploading images/files to a server
Syncing data between app and server
Sending logs to a server
Executing expensive operations on data
When to use WorkManager?
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Dependencies
dependencies {
def work_version = "2.2.0"
implementation "androidx.work:work-runtime-ktx:$work_version"
}
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WorkManager - main components
Worker WorkRequest WorkManager
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Create
Worker
JobScheduler
API 23+?
AlarmManager +
Broadcast Receiver
NO
YES Play
Services?
Firebase
JobDispatcher
NO
YES
Internal mechanism
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Worker
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Worker
doWork()
Result
FAILURE SUCCESS RETRY
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class SyncWorker(c: Context, wp: WorkerParameters):Worker(c, wp) {
override fun doWork(): Result {
loadData()
return Result.success()
}
}
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class SyncWorker(c: Context, wp: WorkerParameters):Worker(c, wp) {
override fun doWork(): Result {
loadData()
return Result.success()
}
}
Runs synchronously on a background thread
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WorkRequest
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Create Worker
OneTimeWorkRequest
Is it
periodic
?
PeriodicWorkRequest
NO YES
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val syncOnlyOnce = OneTimeWorkRequestBuilder().build()
val syncPeriodically = PeriodicWorkRequestBuilder(1,
TimeUnit.HOURS).build()
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OneTimeWorkRequest
● It is used for non-repeating work
● It could have an initial delay
● It could be part of a chain or graph of work
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PeriodicWorkRequest
● Used for tasks that need to execute periodically
● It could have an initial delay
● The minimum repeat interval that can be defined is 15 minutes (same as the
JobScheduler API)
● It cannot be part of a chain or graph of work
● The execution may be delayed because WorkManager is subject to OS battery
optimizations, such as doze mode
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val periodicRefreshRequest = PeriodicWorkRequest.Builder(
SyncWorker::class.java, // the worker class
30, // repeating interval
TimeUnit.Minutes,
15, // flex interval - worker will run somehow within
this period of time, but at the end of repeating interval
TimeUnit.MINUTES
)
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Constraints
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Set constraints
setRequiredNetworkType(requiredNetworkType: NetworkType)
setRequiresBatteryNotLow(requiresBatteryNotLow: Boolean)
setRequiresCharging(requiresCharging: Boolean)
setRequiresDeviceIdle(requiresDeviceIdle: Boolean)
setRequiresStorageNotLow(requiresStorageNotLow: Boolean)
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NetworkType
CONNECTED // Any working network connection
METERED // A metered network connection
NOT_REQUIRED // A network is not required for this work.
NOT_ROAMING // A non-roaming network connection
UNMETERED // An unmetered network connection
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val constraints = Constraints.Builder()
.setRequiresCharging(true)
.setRequiresStorageNotLow(true)
.setRequiredNetworkType(NetworkType.CONNECTED)
.build()
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setConstraints(constraints)
.build()
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Input & Output Data
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putBoolean / getBoolean putBooleanArray / getBooleanArray
putDouble / getDouble putDoubleArray / getDoubleArray
putFloat / getFloat putFloatArray / getFloatArray
putInt / getInt putIntArray / getIntArray
putLong / getLong putLongArray / getLongArray
putString / getString putStringArray / getStringArray
putByte / getByte putByteArray / getByteArray
Data and Data.Builder* (key-value pairs)
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val userIdData = Data.Builder()
.putInt(DATA_USER_ID, userId)
.build()
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setInputData(userIdData)
.build()
val userIdInput = inputData.getInt(Constants.DATA_USER_ID, 0)
// ktx
val outputData = workDataOf(Constants.DATA_SENT to isDataSent)
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Tagging Work
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val userIdData = Data.Builder()
.putInt(DATA_USER_ID, userId)
.build()
val userIdInput = inputData.getInt(Constants.DATA_USER_ID, 0)
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setInputData(userIdData)
.addTag(Constants.WORKER_SYNC)
.build()
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val userIdData = Data.Builder()
.putInt(DATA_USER_ID, userId)
.build()
val userIdInput = inputData.getInt(Constants.DATA_USER_ID, 0)
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setInputData(userIdData)
.addTag(Constants.WORKER_SYNC)
.addTag(Constants.ONE_SYNC)
.build()
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Unique Work
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WorkManager.getInstance(context)
.enqueueUniquePeriodicWork(
Constants.UNIQUE_NAME,
ExistingPeriodicWorkPolicy.KEEP,
syncPeriodically
)
Unique work sequence
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WorkManager.getInstance(context)
.beginUniqueWork(Constants.UNIQUE_NAME,
ExistingWorkPolicy.REPLACE, task1)
.then(task2)
.then(task3)
.enqueue()
Unique work chain
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Existing Work Policy enums
● KEEP - keeps the existing unfinished WorkRequest. Enqueues it if one does
not already exist.
● REPLACE - always replace the WorkRequest. Cancels and deletes the old
one, if it exists.
● APPEND - appends work to an existing chain or create a new chain.
KEEP + REPLACE + APPEND = ExistingWorkPolicy
KEEP + REPLACE = ExistingPeriodicWorkPolicy
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Delays and Retries
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/* Used to indicate that WorkManager should increase the backoff
time exponentially */
EXPONENTIAL
/* Used to indicate that WorkManager should increase the backoff
time linearly */
LINEAR
BackoffPolicy enum
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// add initial delay for OneTimeWorkRequest
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setInitialDelay(15, TimeUnit.MINUTES)
.build()
// backoff delay and policy
val syncOnlyOnce = OneTimeWorkRequestBuilder()
.setBackoffCriteria(BackoffPolicy.LINEAR,
OneTimeWorkRequest.MIN_BACKOFF_MILLIS,
TimeUnit.MICROSECONDS)
.build()
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Work Status
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WorkInfo
UUID State Data Tags
BLOCKED
CANCELLED
ENQUEUED
FAILED
RUNNING
SUCCEEDED
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WorkInfo
Id
WorkManager.getWorkInfoById(UUID)
WorkManager.getWorkInfoByIdLiveData(UUID)
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WorkInfo
Id
WorkManager.getWorkInfoById(UUID)
WorkManager.getWorkInfoByIdLiveData(UUID)
Tag
WorkManager.getWorkInfosByTag(String)
WorkManager.getWorkInfosByTagLiveData(String)
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WorkInfo
Unique Name
WorkManager.getWorkInfosForUniqueWork(String)
WorkManager.getWorkInfosForUniqueWorkLiveData(String)
Id
WorkManager.getWorkInfoById(UUID)
WorkManager.getWorkInfoByIdLiveData(UUID)
Tag
WorkManager.getWorkInfosByTag(String)
WorkManager.getWorkInfosByTagLiveData(String)
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LiveData & WorkManager
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WorkManager.getInstance().getWorkInfoByIdLiveData(syncOnlyOnce.id)
.observe(this, Observer { workInfo ->
if (workInfo != null &&
workInfo.state == State.SUCCEEDED) {
displayMessage("Sync finished!")
}
})
Id
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WorkManager.getInstance().getWorkInfoByIdLiveData(syncOnlyOnce.id)
.observe(this, Observer { workInfo ->
if (workInfo != null &&
workInfo.state == State.SUCCEEDED) {
displayMessage("Sync finished!")
}
})
LiveData
Id
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WorkManager.getInstance()
.getWorkInfosByTagLiveData(Constants.TAG_SYNC)
.observe(this,
Observer> { workStatusList ->
val currentWorkStatus = workStatusList ?.getOrNull(0)
if (currentWorkStatus ?.state ?.isFinished == true) {
displayMessage("Sync finished!")
}
})
Tag
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WorkManager.getInstance()
.getWorkInfosByTagLiveData(Constants.TAG_SYNC)
.observe(this,
Observer> { workStatusList ->
val currentWorkStatus = workStatusList ?.getOrNull(0)
if (currentWorkStatus ?.state ?.isFinished == true) {
displayMessage("Sync finished!")
}
})
LiveData>
Tag
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WorkManager.getInstance()
.getWorkInfosForUniqueWorkLiveData(Constants.UNIQUE_NAME)
.observe(this,
Observer> { workStatusList ->
val currentWorkStatus = workStatusList ?.getOrNull(0)
if (currentWorkStatus ?.state ?.isFinished == true) {
displayMessage("Sync finished!")
}
})
Unique name
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WorkManager.getInstance()
.getWorkInfosForUniqueWorkLiveData(Constants.UNIQUE_NAME)
.observe(this,
Observer> { workStatusList ->
val currentWorkStatus = workStatusList ?.getOrNull(0)
if (currentWorkStatus ?.state ?.isFinished == true) {
displayMessage("Sync finished!")
}
})
LiveData>
Unique name
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Happy path - One Time Work
BLOCKED RUNNING SUCCEEDED
ENQUEUED
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“Unhappy” path - One Time Work
FAILED
CANCELLED
CANCEL
FAILURE
RETRY
BLOCKED RUNNING
ENQUEUED SUCCEEDED
SUCCESS
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“Unhappy” path - Periodic Work
RUNNING
ENQUEUED
CANCELLED
CANCEL
SUCCESS
RETRY, FAILURE
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WorkManager
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enqueue beginWith beginUniqueWork
cancel
WorkManager
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Chaining Tasks
Task 1
Task 2
Task 3
Input
Output
Input
Output
Input
Output
Outputs are Inputs to
child tasks
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WorkManager.getInstance(context)
.beginWith(task1)
.then(task2)
.then(task3)
.enqueue()
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WorkManager.getInstance(context)
.beginWith(task1)
.then(task2)
.then(task3)
.enqueue()
WorkContinuation
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Task 1 Task 2
Task 3
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WorkManager.getInstance(context)
.beginWith(listOf(task1, task2))
.then(task3)
.enqueue()
WorkContinuation
Parallel execution
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Task 1
Task 2
Task 3
Task 4
Task 5
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val leftChain = WorkManager.getInstance(context)
.beginWith(task1)
.then(task2)
val rightChain = WorkManager.getInstance(context)
.beginWith(task3)
.then(task4)
val resultChain = WorkContinuation
.combine(listOf(leftChain, rightChain))
.then(task5)
resultChain.enqueue()
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InputMerger
+merge(): Data
ArrayCreatingInputMerger OverwritingInputMerger
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Key Value
user_id 23
name “Android Pie”
ArrayCreatingInputMerger
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Key Value
user_id 23
name “Android Pie”
Key Value
user_id 37
name “Android 10”
token “211-war-qw2-akjda”
ArrayCreatingInputMerger
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Key Value
user_id 23
name “Android Pie”
Key Value
user_id 37
name “Android 10”
token “211-war-qw2-akjda”
ArrayCreatingInputMerger
Key Value
user_id {23, 37}
name {“Android Pie”, “Android 10”}
token {“211-war-qw2-akjda”}
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Key Value
user_id 23
name “Android Pie”
Key Value
user_id “37”
name “Android 10”
token “211-war-qw2-akjda”
ArrayCreatingInputMerger
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Key Value
user_id 23
name “Android Pie”
Key Value
user_id “37”
name “Android 10”
token “211-war-qw2-akjda”
ArrayCreatingInputMerger
Key Value
user_id IllegalArgumentException
name {“Android Pie”, “Android 10”}
token {“211-war-qw2-akjda”}
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Key Value
user_id 23
name “Android Pie”
points 350
OverwritingInputMerger
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Key Value
user_id 23
name “Android Pie”
points 350
Key Value
user_id “37”
name “Android 10”
token “211-war-qw2-akjda”
OverwritingInputMerger
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Key Value
user_id 23
name “Android Pie”
points 350
Key Value
user_id “37”
name “Android 10”
token “211-war-qw2-akjda”
OverwritingInputMerger
Key Value
user_id 23
name “Android Pie”
points 350
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Key Value
user_id 23
name “Android Pie”
points 350
Key Value
user_id “37”
name “Android 10”
token “211-war-qw2-akjda”
OverwritingInputMerger
Key Value
user_id “37”
name “Android 10”
points 350
token “211-war-qw2-akjda”
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val merge = OneTimeWorkRequestBuilder()
.setInputMerger(ArrayCreatingInputMerger::class.java)
.setConstraints(constraints)
.build()
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// running work
WorkManager.getInstance(context).enqueue(syncOnlyOnce)
// cancelling work
WorkManager.getInstance().cancelAllWork()
WorkManager.getInstance().cancelAllWorkByTag(Constants.TAG_SYNC)
WorkManager.getInstance().cancelUniqueWork(Constants.UNIQUE_NAME)
WorkManager.getInstance().cancelWorkById(UUID.fromString(Constants
.UNIQUE_UDID))
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// running work
WorkManager.getInstance(context).enqueue(syncOnlyOnce)
// cancelling work
WorkManager.getInstance(context).cancelAllWork()
WorkManager.getInstance().cancelAllWorkByTag(Constants.TAG_SYNC)
WorkManager.getInstance().cancelUniqueWork(Constants.UNIQUE_NAME)
WorkManager.getInstance().cancelWorkById(UUID.fromString(Constants
.UNIQUE_UDID))
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// running work
WorkManager.getInstance(context).enqueue(syncOnlyOnce)
// cancelling work
WorkManager.getInstance(context).cancelAllWork()
WorkManager.getInstance(context).cancelAllWorkByTag(Constants.TAG_SYNC)
WorkManager.getInstance().cancelUniqueWork(Constants.UNIQUE_NAME)
WorkManager.getInstance().cancelWorkById(UUID.fromString(Constants
.UNIQUE_UDID))
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// running work
WorkManager.getInstance(context).enqueue(syncOnlyOnce)
// cancelling work
WorkManager.getInstance(context).cancelAllWork()
WorkManager.getInstance(context).cancelAllWorkByTag(Constants.TAG_SYNC)
WorkManager.getInstance(context).cancelUniqueWork(Constants.UNIQUE_NAME)
WorkManager.getInstance().cancelWorkById(UUID.fromString(Constants
.UNIQUE_UDID))
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// running work
WorkManager.getInstance(context).enqueue(syncOnlyOnce)
// cancelling work
WorkManager.getInstance(context).cancelAllWork()
WorkManager.getInstance(context).cancelAllWorkByTag(Constants.TAG_SYNC)
WorkManager.getInstance(context).cancelUniqueWork(Constants.UNIQUE_NAME)
WorkManager.getInstance(context).cancelWorkById(UUID.fromString(Constants
.UNIQUE_UDID))
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Threading options
1. ListenableWorker
2. Worker
3. CoroutineWorker
4. RxWorker
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Threading in WorkManager
Worker
WorkRequest Executor
Internal
TaskExecutor
Database
enqueue execute
Constraints met
WorkerFactory
Credit: Working with WorkManager Presentation Android Developer Summit 2018
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androidx.work.workdb
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WorkSpec table
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ListenableWorker
+startWork(): ListenableFuture
Worker CoroutineWorker RxWorker
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ListenableWorker
Overview
● A ListenableWorker only signals when the work should start and stop
● The start work signal is invoked on the main thread, so we go to a background
thread of our choice manually
● A ListenableFuture is a lightweight interface: it is a Future that provides
functionality for attaching listeners and propagating exceptions
Stop work
● It is always cancelled when the work is expected to stop. Use a
CallbackToFutureAdapter to add a cancellation listener
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Worker
Overview
● Worker.doWork() is called on a background thread, synchronously
● The background thread comes from the Executor specified in
WorkManager's Configuration, but it could also be customised
Stop work
● Worker.onStopped() is called. This method could be overridden or we could
call Worker.isStopped() to checkpoint the code and free up resources
when necessary
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CoroutineWorker
Overview
● For Kotlin users, WorkManager provides first-class support for coroutines
● Instead of extending Worker, we should extend CoroutineWorker
● CoroutineWorker.doWork() is a suspending function
● The code runs on Dispatchers.Default, not on Executor (customisation
by using CoroutineContext)
Stop work
● CoroutineWorkers handle stoppages automatically by cancelling the
coroutine and propagating the cancellation signals
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RxWorker
Overview
● For RxJava2 users, WorkManager provides interoperability
● Instead of extending Worker, we should extend RxWorker
● RxWorker.createWork() method returns a Single indicating the
Result of the execution, and it is called on the main thread, but the return
value is subscribed on a background thread by default. Override
RxWorker.getBackgroundScheduler() to change the subscribing thread.
Stop work
● Done by default
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4
Agenda
Summary
1
3
2
Android Memory Model
Background processing solutions
WorkManager
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WorkManager - Recap
● WorkManager is a wrapper for the existing background processing solutions
● Create one time or periodic work requests
● Identify our tasks by using ids, tags and unique names
● Add constraint, delay and retry policy
● Use input/output data and merge them
● Create chains of tasks
● Use the available threading options
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Resources
● Official Documentation and Official Reference
● Working with WorkManager (Android Dev Summit ’18)
● Android Jetpack: easy background processing with WorkManager (Google
I/O '18)
● https://medium.com/@magdamiu
● Icons from https://www.flaticon.com
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Thank you!
Magda Miu @magdamiu
Squad Lead Developer at Orange
Android Google Developer Expert