flutter_dio_download_file.dart

Future<void> downloadFile() async {
    downloading = true;

    Dio dio = Dio();

    try {
      var dir = await getApplicationDocumentsDirectory();     
      await dio.download(
          "https://piccity/223433.png",
          "${dir.path}/downloaded.png",
          onReceiveProgress: (rec, total) {
            print("Rec: $rec , Total: $total");
          });
    } catch (e) {
       print(e);
    }

    print("Download completed");
  }