Android WorkManager 2026: คู่มือฉบับสมบูรณ์ Background Tasks, Constraints และคำถามสัมภาษณ์งาน

dependencies {
    val workVersion = "2.11.2"
    implementation("androidx.work:work-runtime-ktx:$workVersion")
    // Optional: for testing
    androidTestImplementation("androidx.work:work-testing:$workVersion")
}

class SyncWorker(
    context: Context,
    params: WorkerParameters
) : Worker(context, params) {

    override fun doWork(): Result {
        // Read input data
        val userId = inputData.getString("user_id") ?: return Result.failure()
        
        return try {
            // Perform sync operation
            val syncService = SyncService.getInstance(applicationContext)
            syncService.syncUserData(userId)
            Result.success()
        } catch (e: IOException) {
            // Retry on network errors
            Result.retry()
        } catch (e: Exception) {
            // Permanent failure
            Result.failure()
        }
    }
}

class UploadWorker(
    context: Context,
    params: WorkerParameters
) : CoroutineWorker(context, params) {

    override suspend fun doWork(): Result {
        val imageUri = inputData.getString("image_uri")
            ?: return Result.failure()
        
        // Progress reporting (visible in WorkInfo observers)
        setProgress(workDataOf("status" to "compressing"))
        
        val compressed = ImageCompressor.compress(imageUri)
        
        setProgress(workDataOf("status" to "uploading"))
        
        return try {
            val response = ApiClient.imageService.upload(compressed)
            val outputData = workDataOf("url" to response.imageUrl)
            Result.success(outputData)
        } catch (e: HttpException) {
            if (e.code() in 500..599) Result.retry()
            else Result.failure()
        }
    }
}

fun scheduleUpload(context: Context, imageUri: String) {
    val constraints = Constraints.Builder()
        .setRequiredNetworkType(NetworkType.UNMETERED) // WiFi only
        .setRequiresBatteryNotLow(true)
        .setRequiresStorageNotLow(true)
        .build()

    val uploadRequest = OneTimeWorkRequestBuilder<UploadWorker>()
        .setConstraints(constraints)
        .setInputData(workDataOf("image_uri" to imageUri))
        .setBackoffCriteria(
            BackoffPolicy.EXPONENTIAL,
            Duration.ofMinutes(1)
        )
        .addTag("upload")
        .build()

    WorkManager.getInstance(context)
        .enqueueUniqueWork(
            "upload_$imageUri",
            ExistingWorkPolicy.KEEP,
            uploadRequest
        )
}

fun processAndUploadImages(context: Context, imageUris: List<String>) {
    val workManager = WorkManager.getInstance(context)

    // Parallel compression workers
    val compressRequests = imageUris.map { uri ->
        OneTimeWorkRequestBuilder<CompressWorker>()
            .setInputData(workDataOf("uri" to uri))
            .build()
    }

    // Single upload worker runs after all compressions complete
    val uploadRequest = OneTimeWorkRequestBuilder<BatchUploadWorker>()
        .setConstraints(
            Constraints.Builder()
                .setRequiredNetworkType(NetworkType.CONNECTED)
                .build()
        )
        .build()

    // Cleanup runs after upload, regardless of success
    val cleanupRequest = OneTimeWorkRequestBuilder<CleanupWorker>()
        .build()

    workManager
        .beginWith(compressRequests) // Parallel
        .then(uploadRequest)          // Sequential
        .then(cleanupRequest)          // Sequential
        .enqueue()
}

fun scheduleDailySync(context: Context) {
    val syncRequest = PeriodicWorkRequestBuilder<SyncWorker>(
        repeatInterval = 6, 
        repeatIntervalTimeUnit = TimeUnit.HOURS,
        flexTimeWindow = 30,
        flexTimeUnit = TimeUnit.MINUTES
    )
        .setConstraints(
            Constraints.Builder()
                .setRequiredNetworkType(NetworkType.CONNECTED)
                .build()
        )
        .addTag("periodic_sync")
        .build()

    WorkManager.getInstance(context)
        .enqueueUniquePeriodicWork(
            "daily_sync",
            ExistingPeriodicWorkPolicy.UPDATE,
            syncRequest
        )
}

class UploadViewModel(application: Application) : AndroidViewModel(application) {

    private val workManager = WorkManager.getInstance(application)

    // Flow-based observation
    fun observeUpload(workId: UUID): Flow<WorkInfo?> {
        return workManager.getWorkInfoByIdFlow(workId)
    }

    // Check if any upload is running
    val activeUploads: Flow<List<WorkInfo>> = 
        workManager.getWorkInfosByTagFlow("upload")
            .map { workInfos ->
                workInfos.filter { it.state == WorkInfo.State.RUNNING }
            }
}

// In Compose UI
@Composable
fun UploadProgress(workId: UUID, viewModel: UploadViewModel) {
    val workInfo by viewModel.observeUpload(workId)
        .collectAsState(initial = null)

    when (workInfo?.state) {
        WorkInfo.State.RUNNING -> {
            val status = workInfo?.progress?.getString("status") ?: "working"
            CircularProgressIndicator()
            Text(status)
        }
        WorkInfo.State.SUCCEEDED -> {
            val url = workInfo?.outputData?.getString("url")
            Text("Uploaded: $url")
        }
        WorkInfo.State.FAILED -> Text("Upload failed")
        else -> {}
    }
}

class MetricsRepository(private val context: Context) {
    
    private val workManager = WorkManager.getInstance(context)

    suspend fun getWorkerMetrics(workerName: String): List<WorkMetricsInfo> {
        val query = WorkMetricsQuery.Builder()
            .setWorkerClassName(workerName)
            .setLimit(100)
            .build()
        
        return workManager.getWorkMetrics(query)
    }

    fun analyzeFailures(metrics: List<WorkMetricsInfo>): Map<Int, Int> {
        // Count stop reasons
        return metrics
            .flatMap { it.stopReasonCounts.entries }
            .groupBy { it.key }
            .mapValues { entry -> entry.value.sumOf { it.value } }
    }
}

@RunWith(AndroidJUnit4::class)
class SyncWorkerTest {

    private lateinit var context: Context

    @Before
    fun setup() {
        context = ApplicationProvider.getApplicationContext()
        val config = Configuration.Builder()
            .setMinimumLoggingLevel(Log.DEBUG)
            .setExecutor(SynchronousExecutor())
            .build()
        WorkManagerTestInitHelper.initializeTestWorkManager(context, config)
    }

    @Test
    fun syncWorker_withValidUserId_succeeds() = runTest {
        val inputData = workDataOf("user_id" to "123")
        
        val worker = TestListenableWorkerBuilder<SyncWorker>(context)
            .setInputData(inputData)
            .build()

        val result = worker.doWork()
        
        assertThat(result).isEqualTo(ListenableWorker.Result.success())
    }

    @Test
    fun syncWorker_withoutUserId_fails() = runTest {
        val worker = TestListenableWorkerBuilder<SyncWorker>(context)
            .build()

        val result = worker.doWork()
        
        assertThat(result).isEqualTo(ListenableWorker.Result.failure())
    }
}

WorkManager.getInstance(context).cancelAllWorkByTag("upload")

val request = OneTimeWorkRequestBuilder<UploadWorker>()
    .setBackoffCriteria(
        BackoffPolicy.EXPONENTIAL,
        Duration.ofSeconds(30) // Initial delay, minimum 10 seconds
    )
    .setBackoffOnSystemInterruption(true) // New in 2.11
    .build()