Introduction to WorkManager Bartosz Ostrowski Lead Software Engineer at GlobalLogic GDG Szczecin @bartoszostrowsk 

What is WorkManager? 

Android Jetpack Components ● Foundations ● Architecture ● Behaviour ● UI 

Architecture Components ● DataBinding ● Room ● WorkManager ● LiveData ● Navigation ● Paging ● ViewModel ● Lifecycle 

What is it for? WorkManager is intended for tasks that are deferrable—that is, not required to run immediately — and required to run reliably even if the app exits or the device restarts. 

Key features ● Compatibility up to Android 4.0 ● Work constraints: network, battery level, ... ● Scheduling single of recurring tasks ● Chaining tasks ● Monitoring and managing scheduled tasks 

Sample scenarios ● Google Drive app - one-time worker for sending scan (waits for WiFi connection to sync) ● Language learning apps (e.g. Duolingo or Memrise) - for daily notifications about new words to learn (recurring worker) ● Instagram - chained worker for more complex tasks: take photo, apply filter, upload to server, share on Facebook and/or Twitter 

Compatibility Backward compatibility up to API 14 ● Devices running API 14-22 : AlarmManager + BroadcastReceiver ● Devices running API 23+: JobScheduler 

Getting started 

Dependencies Top-level build.gradle allprojects { repositories { google() jcenter() } } 

dependencies { def work_version = "2.3.1" // (Java only) implementation "androidx.work:work-runtime:$work_version" // Kotlin + coroutines implementation "androidx.work:work-runtime-ktx:$work_version" // RxJava2 support implementation "androidx.work:work-rxjava2:$work_version" // GCMNetworkManager support implementation "androidx.work:work-gcm:$work_version" // Test helpers androidTestImplementation "androidx.work:work-testing:$work_version" } 

class SampleWorker(ctx: Context, params: WorkerParameters) : Worker(ctx, params) { override fun doWork(): Result { // Do sth! return Result.success() } } val request: OneTimeWorkRequest = OneTimeWorkRequest.Builder(SampleWorker::class.java) .build() WorkManager.getInstance(applicationContext).enqueue(request) 

Supported constraints ● Network connection (by type: connected, metered, unmetered, not required, not roaming) ● Battery not low ● Charging ● Storage not low ● Device idle 

val constraints = Constraints.Builder() .setRequiresBatteryNotLow(true) .setRequiredNetworkType(NetworkType.UNMETERED) .setRequiresCharging(false) .setRequiresStorageNotLow(true) .setRequiresDeviceIdle(true) .build() val request: OneTimeWorkRequest = OneTimeWorkRequest.Builder(SampleWorker::class.java) .setConstraints(constraints) .build() 

What if the job fails? Work may finish with the following results: ● SUCCESS ● RETRY ● FAILURE WorkManager has defined back-off policies: ● LINEAR ● EXPONENTIAL 

// Request builder val retryingRequest = OneTimeWorkRequest.Builder(RetryingWorker::class.java) .setBackoffCriteria(BackoffPolicy.LINEAR, 1, TimeUnit.MINUTES) .build() WorkManager.getInstance(applicationContext).enqueue(retryingRequest) // Worker override fun doWork(): Result { if (runAttemptCount > 3) { return Result.failure() } return Result.retry() } 

Repeating task ● Dedicated for regular, cyclic tasks, e.g. database backup ● Can be scheduled with minimal 15 minute frequency ● Cannot be used as a timer. It is not fully deterministic in timely manner. 

val request = PeriodicWorkRequest .Builder(RecurringWorker::class.java, 4, TimeUnit.HOURS) .build() WorkManager.getInstance(applicationContext) .enqueueUniquePeriodicWork("recurring", ExistingPeriodicWorkPolicy.REPLACE, request) WorkManager.getInstance(applicationContext) .enqueueUniquePeriodicWork("recurring", ExistingPeriodicWorkPolicy.KEEP, request) 

Old vs. new approach... … for cyclic notifications ● Boot complete broadcast receiver ● App update broadcast receiver ● Manifest update: permissions, receivers ● Maintaining AlarmManager for notifications ● Worker + request builder Old New 

Chaining work ● Can be scheduled to run in parallel ● Can be schedule to run sequentially, feeding latter worker with a result of the prior task. 

Proprietary + Confidential Source: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis non erat sem Chaining work 

WorkManager.getInstance(applicationContext) .beginWith(listOf(blur, noise, glow)) .then(compress) .then(upload) .enqueue() 

class UploadWorker(ctx: Context, params: WorkerParameters) : Worker(ctx, params) { override fun doWork(): Result { val input = inputData.getString("value") val time = System.currentTimeMillis() // Fake job for 15 seconds Thread.sleep(15000) val output = Data.Builder() .putString("value", "$input + UPLOAD") .build() Log.d(TAG, "doWork() : Work is done. Took = " + (System.currentTimeMillis() - time) + " ms. Output = " + output.getString("value")) return Result.success(output) } 

class CompressWorker(ctx: Context, params: WorkerParameters) : Worker(ctx, params) { override fun doWork(): Result { val input = inputData.getString("value") val time = System.currentTimeMillis() // Fake job for 15 seconds Thread.sleep(15000) val output = Data.Builder() .putString("value", "$input + COMPRESS") .build() Log.d(TAG, "doWork() : Work is done. Took = " + (System.currentTimeMillis() - time) + " ms. Output = " + output.getString("value")) return Result.success(output) } 

Chaining work... InputMergers ● OverwritingInputMerger ● ArrayCreatingInputMerger 

val output = Data.Builder() .putString("keyA", "value1") .putInt("keyB", 1) .putString("keyC", "valueC") .build() val output = Data.Builder() .putString("keyA", "value2") .putInt("keyB", 2) .putString("keyD", "valueD") .build() // Result of Worker3 -> {keyA = value1, keyB = 1, keyC = valueC, keyD = valueD} // or // Result of Worker3 -> {keyA = value2, keyB = 2, keyC = valueC, keyD = valueD} 

val output = Data.Builder() .putString("keyA", "value1") .putInt("keyB", 1) .putString("keyC", "valueC") .build() val output = Data.Builder() .putString("keyA", "value2") .putInt("keyB", 2) .putString("keyD", "valueD") .build() // keyA = [value1, value2] // keyB = [1, 2] // keyC = [valueC] // keyD = [valueD] 

Further topics to cover ● Testing ● Conjunction with LiveData and RxJava ● Getting statuses of a worker ● Cancelling and stopping workers ● Existing workers - replace, keep, append ● News in WorkManager - e.g. LongWorker 

Reference ● Android Developer Documentation ● Background work with WorkManager - Codelabs ● WorkManager Basics - Article on Medium ● InputMerger with WorkManager ● https://github.com/bartoszostrowski/WorkManagerExample 

Thank You! Bartosz Ostrowski Lead Software Engineer at GlobalLogic GDG Szczecin @bartoszostrowsk