使用 Android 中的下载管理器下载后识别特定文件

Question

I am calling below function to download a binary file.

fun downloadFile(
        baseActivity: Context,
        batteryId: String,
        downloadFileUrl: String?,
        title: String?
    ): Long {
        val directory =
            File(Environment.getExternalStorageDirectory().toString() + "/destination_folder")

        if (!directory.exists()) {
            directory.mkdirs()
        }
        //Getting file extension i.e. .bin, .mp4 , .jpg, .png etc..
        val fileExtension = downloadFileUrl?.substring(downloadFileUrl.lastIndexOf("."))
        val downloadReference: Long
        var objDownloadManager: DownloadManager =
            baseActivity.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
        val uri = Uri.parse(downloadFileUrl)
        val request = DownloadManager.Request(uri)

        //Firmware file name as batteryId and extension
        firmwareFileSubPath = batteryId + fileExtension
        request.setDestinationInExternalPublicDir(
            Environment.DIRECTORY_DOWNLOADS,
            "" + batteryId + fileExtension
        )
        request.setTitle(title)
        downloadReference = objDownloadManager.enqueue(request) ?: 0

        return downloadReference
    }

Once the file got downloaded I am receiving it in below onReceive() method of Broadcast receiver:

override fun onReceive(context: Context, intent: Intent) {
                if (intent.action == DownloadManager.ACTION_DOWNLOAD_COMPLETE) {
                    intent.extras?.let {
                        //retrieving the file
                        val downloadedFileId = it.getLong(DownloadManager.EXTRA_DOWNLOAD_ID)
                        val downloadManager =
                            getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
                        val uri: Uri = downloadManager.getUriForDownloadedFile(downloadedFileId)
                        viewModel.updateFirmwareFilePathToFirmwareTable(uri)
                    }
                }
            }

I am downloading the files one by one and wants to know that which file is downloaded. Based on the particular file download, I have to update the entry in my local database.

So, here in onReceive() method how can I identify that which specific file is downloaded?

Thanks.

Answer 1

You have the Uri of file, now simply get the file name to identify the file, you can use following function to get file name

fun getFileName(uri: Uri): String?  {
    var result: String? = null
    when(uri.scheme){
        "content" -> {
             val cursor: Cursor? = getContentResolver().query(uri, null, null, null, null)
             cursor.use {
                 if (it != null && it.moveToFirst()) {
                     result = it.getString(it.getColumnIndex(OpenableColumns.DISPLAY_NAME))
                 }
             }
        }
        else -> {
            val lastSlashIndex = uri.path?.lastIndexOf('/')
            if(lastSlashIndex != null && lastSlashIndex != -1) {
                 result = uri.path!!.substring(lastSlashIndex + 1)
            }
        }
    }
    return result
}

Answer 2

One way to identify your multiple downloads simultaneously is to track id returned from DownloadManager to your local db mapped to given entry when you call objDownloadManager.enqueue(request) .

Document of DownloadManager.enquque indicates that:

Enqueue a new download. The download will start automatically once the download manager is ready to execute it and connectivity is available.

So, if you store that id mapped to your local database entry for given record then during onReceive() you can identify back to given record.

override fun onReceive(context: Context, intent: Intent) {
            if (intent.action == DownloadManager.ACTION_DOWNLOAD_COMPLETE) {
                intent.extras?.let {
                    //retrieving the file
                    val downloadedFileId = it.getLong(DownloadManager.EXTRA_DOWNLOAD_ID)
                    // Find same id from db that you stored previously
                    val downloadManager =
                        getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
                    val uri: Uri = downloadManager.getUriForDownloadedFile(downloadedFileId)
                    viewModel.updateFirmwareFilePathToFirmwareTable(uri)
                }
            }
        }

Here, it.getLong(DownloadManager.EXTRA_DOWNLOAD_ID) returns you the same id for which download was started previously and enqueue returned.

Document for EXTRA_DOWNLOAD_ID indicates that:

Intent extra included with ACTION_DOWNLOAD_COMPLETE intents, indicating the ID (as a long) of the download that just completed.