Android Background Processing
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Next episode: 22. Conclusion
Notes: 21. Challenge - Communication Between Components
The student materials have been reviewed and are updated as of SEPTEMBER 2022.
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To really understand Services and BroadcastReceivers, and the communication between such components, you have to solve a small challenge! :]
const val ACTION_IMAGE_UPLOAD = "image_upload"
class UploadImageReceiver(
private inline val onImageUploaded: (Boolean) -> Unit) : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
if (intent?.action == ACTION_IMAGE_UPLOAD) {
val isUploaded = intent.getBooleanExtra("is_uploaded", false)
onImageUploaded(isUploaded)
}
}
}
class UploadService : JobIntentService() {
private val remoteApi by lazy { App.remoteApi }
}
<service
android:name=".service.UploadService"
android:permission="android.permission.BIND_JOB_SERVICE" />
class UploadService : JobIntentService() {
private val remoteApi by lazy { App.remoteApi }
companion object {
private const val JOB_ID = 52
fun startWork(context: Context, intent: Intent) {
enqueueWork(context, UploadService::class.java, JOB_ID, intent)
}
}
...
}
class UploadService : JobIntentService() {
...
override fun onHandleWork(intent: Intent) {
val filePath = intent.getStringExtra("image_path")
if (filePath != null) {
uploadImage(filePath)
}
}
...
}
class UploadService : JobIntentService() {
...
private fun uploadImage(filePath: String) {
GlobalScope.launch {
val result = remoteApi.uploadImage(File(filePath))
val intent = Intent()
intent.putExtra("is_uploaded", result.message == "Success!")
intent.action = ACTION_IMAGE_UPLOAD
sendBroadcast(intent)
}
}
...
}
private val synchronizeImagesReceiver by lazy {
SynchronizeImagesReceiver {
toast("Images synchronized!")
}
}
private val uploadImageReceiver by lazy {
UploadImageReceiver { isUploaded ->
toast(if (isUploaded) "Image uploaded!" else "Upload failed! :[")
}
}
registerReceiver(synchronizeImagesReceiver, IntentFilter().apply {
addAction(ACTION_IMAGES_SYNCHRONIZED)
})
registerReceiver(uploadImageReceiver, IntentFilter().apply {
addAction(ACTION_IMAGE_UPLOAD)
})
override fun onStop() {
...
unregisterReceiver(uploadImageReceiver)
super.onStop()
}
val intent = Intent().apply { putExtra("image_path", fileUri) }
UploadService.startWork(requireContext(), intent)