Android: Kotlin: running tasks upon app closing

Question

While a user moves around my app I collect key events in a list. When the user quits the app I want to:

1. write that list to a file; and
2. upload that file to the cloud for analysis on the backend

I put everything in a function and unit-tested, and it works fine so long as the app is still active. But:

1. calling the function from the MainActivity onStop() doesn't upload the file to the cloud (it is written to the device successfully)
2. ditto onPause()
3. I tried to send a completableDeferred to the function and .await for it, but that didn't help either (I used a coroutine scope initiated by MainActivity).

I've heard before the edict "Though shalt not mess with the lifecycle events", so I guess this is a confirmation...

How do you suggest I accomplish this (upload the file to the cloud when the user quits the app)? It doesn't need to be immediate, it just needs to happen eventually.

Thank you!

Answer 1

Maybe try to use WorkManager. It can work in background

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

    override fun doWork(): Result {
        val filePath = inputData.getString("filePath") ?: return Result.failure()

        return try {
            val file = File(filePath)
            if (file.exists()) {
                uploadToCloud(file)
                Result.success()
            } else {
                Result.failure()
            }
        } catch (e: Exception) {
            e.printStackTrace()
            Result.retry()
        }
    }

    private fun uploadToCloud(file: File) {
        // ...
    }
}

And start it from Activity onStop

override fun onStop() {
    super.onStop()

    val filePath = saveEventsToFile()

    val data = Data.Builder()
        .putString("filePath", filePath)
        .build()

    val uploadWorkRequest = OneTimeWorkRequestBuilder<FileUploadWorker>()
        .setInputData(data)
        .build()

    WorkManager.getInstance(applicationContext).enqueue(uploadWorkRequest)
}

private fun saveEventsToFile(): String {
    val filePath = "${filesDir.path}/events.json"
    return filePath
}