Create files in Android's external folder

android-file-exporter.kt

/**
 * Exports file to the given target folder on Android.
 *
 * ref: https://stackoverflow.com/questions/75055593/access-images-in-external-storage-created-by-my-app
 */
@Throws(IOException::class)
suspend fun exportImage(
    contentResolver: ContentResolver,
    file: File,
    targetFolder: String,
    rootDirectory: String = Environment.DIRECTORY_PICTURES
) = withContext(Dispatchers.IO) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        saveImageApi29(contentResolver, file, targetFolder, rootDirectory)
    } else {
        saveImageLegacy(contentResolver, file, targetFolder, rootDirectory)
    }
}

@RequiresApi(29)
@Throws(IOException::class)
private fun saveImageApi29(
    contentResolver: ContentResolver,
    file: File,
    targetFolder: String,
    rootDirectory: String
) {
    val contentUri = MediaStore.Images.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
    val path = "$rootDirectory/$targetFolder"

    val projection = ContentValues().apply {
        put(MediaStore.Images.Media.DISPLAY_NAME, file.name)
        put(MediaStore.Images.Media.SIZE, file.length())
        put(MediaStore.Images.Media.RELATIVE_PATH, path)
    }
    contentResolver.insert(contentUri, projection)?.also { uri ->
        contentResolver.openOutputStream(uri)?.use { outputStream ->
            val fileStream = FileInputStream(file)
            fileStream.copyTo(outputStream)
        }
    } ?: throw IOException("Can't create file ${file.name} in path $path")
}

@Throws(IOException::class)
private fun saveImageLegacy(
    contentResolver: ContentResolver,
    file: File,
    targetFolder: String,
    rootDirectory: String
) {

    val collection = MediaStore.Images.Media.EXTERNAL_CONTENT_URI
    val dir = Environment.getExternalStoragePublicDirectory(rootDirectory).absolutePath + "/$targetFolder"
    val directory = File(dir)
    if (!directory.exists())
        directory.mkdirs()
    val image = File(dir, file.name)
    val values = ContentValues().apply {
        put(MediaStore.Images.Media.DISPLAY_NAME, image.name)
        put(MediaStore.Images.Media.SIZE, image.length())
        put(MediaStore.Images.Media.MIME_TYPE, "image/png")
        put(MediaStore.Images.Media.DATA, image.path)
    }
    contentResolver.insert(collection, values)?.also { uri ->
        contentResolver.openOutputStream(uri)?.use { outputStream ->
            val fileStream = FileInputStream(file)
            fileStream.copyTo(outputStream)
        }
    } ?: throw IOException("Can't create file ${file.name} in path $dir")
}