Android Background Processing
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Next episode: 26. Schedule Work With AlarmManager
Notes: 25. Use the JobScheduler
The student materials have been reviewed and are updated as of SEPTEMBER 2022.
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The next legacy mechanism you’ll use for background processing is the JobScheduler. It’s actually very similar to how the WorkManager is implemented. But it has some key differences when it comes to communicating the Result output data.
class DownloadImageJobService : JobService() {
override fun onStartJob(params: JobParameters?): Boolean {
val imagePath = params?.extras?.getString("image_path")
}
}
<service
android:name=".DownloadImageJobService"
android:permission="android.permission.BIND_JOB_SERVICE" />
class DownloadImageJobService : JobService() {
override fun onStartJob(params: JobParameters?): Boolean {
val imagePath = params?.extras?.getString("image_path")
return if (imagePath != null) {
downloadImage(imagePath)
true
} else {
jobFinished(null, false)
false
}
}
private fun downloadImage(imageDownloadPath: String) {
Thread(Runnable {
}).start()
}
}
class DownloadImageJobService : JobService() {
override fun onStartJob(params: JobParameters?): Boolean {
val imagePath = params?.extras?.getString("image_path")
return if (imagePath != null) {
downloadImage(imagePath)
true
} else {
jobFinished(null, false)
false
}
}
private fun downloadImage(imageDownloadPath: String) {
Thread(Runnable {
val imageUrl = URL(imageDownloadPath)
val connection = imageUrl.openConnection() as HttpURLConnection
connection.doInput = true
connection.connect()
val imagePath = "owl_image_${System.currentTimeMillis()}.jpg"
val inputStream = connection.inputStream
val file = File(applicationContext.externalMediaDirs.first(), imagePath)
}).start()
}
}
class DownloadImageJobService : JobService() {
...
private fun downloadImage(imageDownloadPath: String) {
Thread(Runnable {
try {
val imageUrl = URL(imageDownloadPath)
val connection = imageUrl.openConnection() as HttpURLConnection
connection.doInput = true
connection.connect()
val imagePath = "owl_image_${System.currentTimeMillis()}.jpg"
val inputStream = connection.inputStream
val file = File(applicationContext.externalMediaDirs.first(), imagePath)
val outputStream = FileOutputStream(file)
outputStream.use { output ->
val buffer = ByteArray(4 * 1024)
var byteCount = inputStream.read(buffer)
while (byteCount > 0) {
output.write(buffer, 0, byteCount)
byteCount = inputStream.read(buffer)
}
output.flush()
}
}).start()
}
}
class DownloadImageJobService : JobService() {
...
private fun downloadImage(imageDownloadPath: String) {
Thread(Runnable {
try {
...
sendBroadcast(Intent().apply {
action = ACTION_IMAGE_DOWNLOADED
putExtra("image_path", file.absolutePath)
})
} catch (error: Throwable) {
jobFinished(null, false)
}
}).start()
}
}
sendBroadcast(Intent().apply {
action = ACTION_IMAGE_DOWNLOADED
putExtra("image_path", file.absolutePath)
})
class DownloadImageJobService : JobService() {
...
override fun onStopJob(params: JobParameters?): Boolean {
return false
}
}
const val ACTION_IMAGE_DOWNLOADED = "image_downloaded"
class ImageDownloadedReceiver(
private val onImageDownloaded: (String) -> Unit
) : BroadcastReceiver() {}
const val ACTION_IMAGE_DOWNLOADED = "image_downloaded"
class ImageDownloadedReceiver(
private val onImageDownloaded: (String) -> Unit
) : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
}
}
const val ACTION_IMAGE_DOWNLOADED = "image_downloaded"
class ImageDownloadedReceiver(
private val onImageDownloaded: (String) -> Unit
) : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
if (intent?.action != ACTION_IMAGE_DOWNLOADED) {
return
}
val imagePath = intent.getStringExtra("image_path")
if (imagePath != null) {
onImageDownloaded(imagePath)
}
}
}
private val receiver by lazy {
ImageDownloadedReceiver {
displayImage(it)
}
}
registerReceiver(receiver, IntentFilter().apply {
addAction(ACTION_IMAGE_DOWNLOADED)
})
override fun onDestroy() {
unregisterReceiver(receiver)
super.onDestroy()
}
val jobScheduler = getSystemService(JobScheduler::class.java) ?: return
const val LOAD_IMAGE_JOB_ID = 10
val jobScheduler = getSystemService(JobScheduler::class.java) ?: return
jobScheduler.schedule(JobInfo.Builder(LOAD_IMAGE_JOB_ID,
ComponentName(this, DownloadImageJobService::class.java))
.build())
val jobScheduler = getSystemService(JobScheduler::class.java) ?: return
jobScheduler.schedule(JobInfo.Builder(LOAD_IMAGE_JOB_ID,
ComponentName(this, DownloadImageJobService::class.java))
.setRequiredNetworkType(JobInfo.NETWORK_TYPE_UNMETERED)
.setExtras(PersistableBundle().apply {
putString("image_path", "https://wallpaperplay.com/walls/full/1/c/7/38027.jpg")
})
.setOverrideDeadline(1500)
.build())