Extension file to handle images from Google Drive

DriveEx.kt

fun Activity?.createTempFile(uri: Uri, callback: DriveTempFileCallback) {
    val startTime = System.currentTimeMillis() // Just for debugging purpose
    this.doAsyncResult {  // Here I have used the Anko library to simplify things
        var stream: InputStream? = null
        try {
            stream = this@createTempFile?.contentResolver?.openInputStream(uri)
        } catch (e: FileNotFoundException) {
            e.printStackTrace()
        }

        val tempFile = File.createTempFile(Date().time.toString(), ".JPEG")
        tempFile.deleteOnExit()
        try {
            IOUtils.copy(stream, FileOutputStream(tempFile))
        } catch (e: FileNotFoundException) {
            e.printStackTrace()
        }
        onComplete {
            val fetchingTime = System.currentTimeMillis() - startTime
            log("Fetching time of file $fetchingTime")
            callback.onFileCreated(tempFile)

            return@onComplete
        }
        return@doAsyncResult tempFile
    }
}

fun Activity?.getUriListFromTempFile(uriList: ArrayList<Uri>, callback: DriveImageCallback) {
    val startTime = System.currentTimeMillis()
    val resultList = arrayListOf<Uri>()
    for (uri in uriList) {
        createTempFile(uri, DriveTempFileCallback {
            resultList.add(Uri.fromFile(it))
            if (resultList.size == uriList.size) {
                callback.onSuccess(resultList)
                val fetchingTime = System.currentTimeMillis() - startTime
                log("Fetching time of all files $fetchingTime")
            }
        })
    }

}