Multipart Upload

Activity.java

// From Camera
Bitmap photo = (Bitmap) data.getExtras().get("data");

File imageFileFolder = new File(getCacheDir(),"Avatar");
if( !imageFileFolder.exists() ){
    imageFileFolder.mkdir();
}

FileOutputStream out = null;

File imageFileName = new File(imageFileFolder, "avatar-" + System.currentTimeMillis() + ".jpg");
try {
    out = new FileOutputStream(imageFileName);
    photo.compress(Bitmap.CompressFormat.JPEG, 100, out);
    out.flush();
} catch (IOException e) {
    Log.e(TAG, "Failed to convert image to JPEG", e);
} finally {
    try {
        if (out != null) {
            out.close();
        }
    } catch (IOException e) {
        Log.e(TAG, "Failed to close output stream", e);
    }
}

TypedFile image = new TypedFile("image/jpeg", imageFileName);

mUserService.uploadAvatar(mAuthToken, image, new Callback<Boolean>() {
    @Override
    public void success(Boolean aBoolean, Response response) {
        Log.v(TAG, "Avatar successfully saved to server");
    }

    @Override
    public void failure(RetrofitError error) {
        Log.e(TAG, "Failed to save user avatar: " + error.getResponse().getReason(), error);
    }
});

UserService.java

    @Multipart
    @POST("/user/me/avatar?access_token={access_token}")
    void uploadAvatar(@Name("access_token") String accessToken, @Name("avatar") TypedFile image, retrofit.http.Callback<Boolean> callback);

This set up results in having multipart params, but no multipart files in the HttpServletRequest on the API side.

Why do I have to save it before uploading? What if I already have the bitmap and I just want to convert that to a bytearray and upload it without saving the image locally to my device? This feature of uploading an image without saving it to the phone should be in your library