android retrofit download progress

Question

I\'m new to retrofit. I\'ve searched but didn\'t found a simple answer. I want to know how can I show progress of download in Notification bar or at least show a progress di

Answer 1

Here is my variant with Kotlin's coroutines

1. Specify API interface. We need @Streaming annotation to say Retrofit that we want to handle response body manually. Otherwise retrofit will try write your file straight into RAM

interface Api {

    @Streaming
    @GET("get-zip-ulr/{id}")
    fun getZip(@Path("id") id: Int): Call
}

2. Create DataSource which will control downloading process

class FilesDataSource(private val parentFolder: File, private val api: Api) {

    suspend fun downloadZip(id: Int, processCallback: (Long, Long) -> Unit): File {
        val response = api.getZip(id).awaitResponse()// returns the response, but it's content will be later
        val body = response.body()
        if (response.isSuccessful && body != null) {
            val file = File(parentFolder, "$id")
            body.byteStream().use { inputStream ->
                FileOutputStream(file).use { outputStream ->
                    val data = ByteArray(8192)
                    var read: Int
                    var progress = 0L
                    val fileSize = body.contentLength()
                    while (inputStream.read(data).also { read = it } != -1) {
                        outputStream.write(data, 0, read)
                        progress += read
                        publishProgress(processCallback, progress, fileSize)
                    }
                    publishProgress(processCallback, fileSize, fileSize)
                }
            }
            return file
        } else {
            throw HttpException(response)
        }
    }

    private suspend fun publishProgress(
        callback: (Long, Long) -> Unit,
        progress: Long, //bytes
        fileSize: Long  //bytes
    ) {
        withContext(Dispatchers.Main) { // invoke callback in UI thtread
            callback(progress, fileSize)
        }
    }
}

Now you can execute downloadZip() method in your ViewModel or Presenter and give it callback which will be linked to some ProgerssBar. After download completion you will receive downloaded file.