How to query and retrieve downloaded files using DownloadManager in Kotlin Android

How to query and retrieve downloaded files using DownloadManager in Kotlin Android.

Here's a step-by-step tutorial on how to query and retrieve downloaded files using DownloadManager in Kotlin Android:

Step 1: Add the necessary permissions to your AndroidManifest.xml file:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Step 2: Create a new Kotlin class, let's call it DownloadHelper, to handle the download process:

import android.app.DownloadManager
import android.content.Context
import android.net.Uri
import android.os.Environment

class DownloadHelper(private val context: Context) {

    fun downloadFile(url: String, fileName: String) {
        val request = DownloadManager.Request(Uri.parse(url))
        request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI or DownloadManager.Request.NETWORK_MOBILE)
        request.setTitle(fileName)
        request.setDescription("Downloading file...")
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)
        request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName)

        val downloadManager = context.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
        downloadManager.enqueue(request)
    }

    fun getDownloadedFiles(): List<DownloadedFile> {
        val downloadManager = context.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
        val query = DownloadManager.Query()
        query.setFilterByStatus(DownloadManager.STATUS_SUCCESSFUL)

        val cursor = downloadManager.query(query)
        val downloadedFiles = mutableListOf<DownloadedFile>()

        if (cursor.moveToFirst()) {
            do {
                val id = cursor.getLong(cursor.getColumnIndex(DownloadManager.COLUMN_ID))
                val title = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_TITLE))
                val uri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI))

                downloadedFiles.add(DownloadedFile(id, title, uri))
            } while (cursor.moveToNext())
        }

        cursor.close()
        return downloadedFiles
    }

    data class DownloadedFile(val id: Long, val title: String, val uri: String)
}

Step 3: In your activity or fragment, create an instance of DownloadHelper and use its methods to download files and retrieve downloaded files:

val downloadHelper = DownloadHelper(context)

// Download a file
downloadHelper.downloadFile("https://example.com/file.pdf", "file.pdf")

// Retrieve downloaded files
val downloadedFiles = downloadHelper.getDownloadedFiles()
for (file in downloadedFiles) {
    Log.d("DownloadedFile", "ID: ${file.id}, Title: ${file.title}, URI: ${file.uri}")
}

That's it! You now have the ability to download files using DownloadManager and retrieve the downloaded files using DownloadHelper in Kotlin Android.

Note: Don't forget to handle the necessary runtime permissions for downloading and saving files in Android 6.0 (Marshmallow) and above.

I hope this tutorial helps you in querying and retrieving downloaded files using DownloadManager in Kotlin Android! If you have any further questions, feel free to ask.