Android Background Processing

Sep 23 2022 · Kotlin 1.6, Android 12, Android Studio Chipmunk 2021.2.1

Part 2: Use WorkManager in Complex Apps

13. Challenge - DownloadManager

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Previous episode: 12. Use DownloadManager Next episode: 14. Conclusion

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Notes: 13. Challenge - DownloadManager

The student materials have been reviewed and are updated as of SEPTEMBER 2022.

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To finish off the WorkManager and DownloadManager practice, you first have to solve a challenge! In this challenge, you have to replace the SynchronizeImageWorker code, with the DownloadManager. Here’s a hint, you can extract the code for the DownloadManager, to the FileUtils, and then reuse it for each image you have to download!

  fun queueImagesForDownload(context: Context, images: Array<String>) {
    if (images.isNotEmpty()) {
      val downloadManager = context.getSystemService(DownloadManager::class.java)

      val requests = images.mapNotNull { imageUrl ->
        val file = File(context.externalMediaDirs.first(), imageUrl)

        buildDownloadManagerRequest(file, imageUrl)
      }

      requests.forEach { request -> downloadManager?.enqueue(request) }
    }
  }
  
private fun buildDownloadManagerRequest(file: File, imageUrl: String): DownloadManager.Request? {
    return DownloadManager.Request(Uri.parse("$BASE_URL/files/$imageUrl"))
        .setTitle("Image download")
        .setDescription("Downloading")
        .setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE)
        .setDestinationUri(Uri.fromFile(file))
        .setAllowedOverMetered(true)
        .setAllowedOverRoaming(false)
  }
FileUtils.queueImagesForDownload(applicationContext, images)
FileUtils.queueImagesForDownload(requireContext(), arrayOf(imageUrl))