How to download a file with Retrofit2?

Question

How can I download a file(image/video) from my PHP server using Retrofit2 ?

I wasn't able to find any resources or tutorials online on how to proceed; I found this post that treats a certain download error on SO but it's not very clear to me. Could anyone point me to the right direction?

UPDATE:

Here is my code:

FileDownloadService.java

public interface FileDownloadService {
    @GET(Constants.UPLOADS_DIRECTORY + "/{filename}")
    @Streaming
    Call<ResponseBody> downloadRetrofit(@Path("filename") String fileName);
}

MainActivity.java (@Blackbelt's solution)

private void downloadFile(String filename) {
    FileDownloadService service = ServiceGenerator
            .createService(FileDownloadService.class, Constants.SERVER_IP_ADDRESS);
    Call<ResponseBody> call = service.downloadRetrofit("db90408a4bb1ee65d3e09d261494a49f.jpg");

    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(final Response<ResponseBody> response, Retrofit retrofit) {
            try {
                InputStream is = response.body().byteStream();
                FileOutputStream fos = new FileOutputStream(
                        new File(Environment.getExternalStorageDirectory(), "image.jpg")
                );
                int read = 0;
                byte[] buffer = new byte[32768];
                while ((read = is.read(buffer)) > 0) {
                    fos.write(buffer, 0, read);
                }

                fos.close();
                is.close();
            } catch (Exception e) {
                Toast.makeText(MainActivity.this, "Exception: " + e.toString(), Toast.LENGTH_LONG).show();
            }
        }

        @Override
        public void onFailure(Throwable t) {
            Toast.makeText(MainActivity.this, "Failed to download file...", Toast.LENGTH_LONG).show();
        }
    });
}

I get a FileNotFoundException when USB debugging is active, & a NetworkOnMainThreadException when not.

MainActivity.java: (@Emanuel's solution)

private void downloadFile(String filename) {
    FileDownloadService service = ServiceGenerator
            .createService(FileDownloadService.class, Constants.SERVER_IP_ADDRESS);
    Call<ResponseBody> call = service.downloadRetrofit("db90408a4bb1ee65d3e09d261494a49f.jpg");

    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(final Response<ResponseBody> response, Retrofit retrofit) {
            Log.i(TAG, "external storage = " + (Environment.getExternalStorageState() == null));
            Toast.makeText(MainActivity.this, "Downloading file... " + Environment.getExternalStorageDirectory(), Toast.LENGTH_LONG).show();

            File file = new File(Environment.getDataDirectory().toString() + "/aouf/image.jpg");
            try {
                file.createNewFile();
                Files.asByteSink(file).write(response.body().bytes());
            } catch (Exception e) {
                Toast.makeText(MainActivity.this,
                        "Exception: " + e.toString(),
                        Toast.LENGTH_LONG).show();
            }
        }

        @Override
        public void onFailure(Throwable t) {
            Toast.makeText(MainActivity.this, "Failed to download file...", Toast.LENGTH_LONG).show();
        }
    });
}

I get a FileNotFoundException.

Answer 1

This is a little example showing how to download the Retrofit JAR file. You can adapt it to your needs.

This is the interface:

import com.squareup.okhttp.ResponseBody;
import retrofit.Call;
import retrofit.http.GET;
import retrofit.http.Path;

interface RetrofitDownload {
    @GET("/maven2/com/squareup/retrofit/retrofit/2.0.0-beta2/{fileName}")
    Call<ResponseBody> downloadRetrofit(@Path("fileName") String fileName);
}

And this is a Java class using the interface:

import com.google.common.io.Files;
import com.squareup.okhttp.ResponseBody;
import retrofit.Call;
import retrofit.Callback;
import retrofit.Response;
import retrofit.Retrofit;

import java.io.File;
import java.io.IOException;

public class Main {

    public static void main(String... args) {
        Retrofit retrofit = new Retrofit.Builder().
                baseUrl("http://repo1.maven.org").
                build();

        RetrofitDownload retrofitDownload = retrofit.create(RetrofitDownload.class);

        Call<ResponseBody> call = retrofitDownload.downloadRetrofit("retrofit-2.0.0-beta2.jar");

        call.enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Response<ResponseBody> response, Retrofit retrofitParam) {
                File file = new File("retrofit-2.0.0-beta2.jar");
                try {
                    file.createNewFile();
                    Files.asByteSink(file).write(response.body().bytes());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onFailure(Throwable t) {
            }
        });
    }
}