Error: Converting object to an encodable object failed: Instance of 'FormData'

[ismailSilkron]

Package

dio

Version

5.8.0

Operating-System

Android

Adapter

Default Dio

Output of flutter doctor -v

Flutter (Channel stable, 3.27.0, on Microsoft Windows [Version 10.0.19045.5371], locale en-MY)
    • Flutter version 3.27.0 on channel stable at C:\flutter_sdk\flutter_v3.27
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 8495dee1fd (9 weeks ago), 2024-12-10 14:23:39 -0800
    • Engine revision 83bacfc525
    • Dart version 3.6.0
    • DevTools version 2.40.2

[√] Windows Version (Installed version of Windows is version 10 or higher)

[√] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
    • Android SDK at C:\Users\Ismail\AppData\Local\Android\sdk
    • Platform android-35, build-tools 35.0.0
    • Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
    • Java version OpenJDK Runtime Environment (build 21.0.3+-12282718-b509.11)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.5.0)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.5.33414.496
    • Windows 10 SDK version 10.0.22000.0

[√] Android Studio (version 2024.2)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 21.0.3+-12282718-b509.11)

[√] VS Code (version 1.97.0)
    • VS Code at C:\Users\Ismail\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.104.0

[√] Connected device (4 available)
    • sdk gphone64 x86 64 (mobile) • emulator-5554 • android-x64    • Android 15 (API 35) (emulator)
    • Windows (desktop)            • windows       • windows-x64    • Microsoft Windows [Version 10.0.19045.5371]
    • Chrome (web)                 • chrome        • web-javascript • Google Chrome 132.0.6834.160
    • Edge (web)                   • edge          • web-javascript • Microsoft Edge 132.0.2957.115

[√] Network resources
    • All expected network resources are available.

Dart Version

3.6.0

Steps to Reproduce

I'm using dio package to upload images/files to my server. However, it gives same error every single time.

Below is the example of code-related snippet:

Future<Result<bool>> _uploadFile(File file) async {
  final String fileName = file.path.split('/').last;

  final FormData formData = FormData.fromMap({
    "api_log": MultipartFile.fromBytes(
      File(file.path).readAsBytesSync(),
      filename: fileName,
      contentType: MediaType.parse("text/plain"),
    ),
  });

  final baseOptions = BaseOptions(
    baseUrl: "https://test.com",
    contentType: Headers.multipartFormDataContentType,
    headers: {},
    connectTimeout: const Duration(seconds: 30),
    receiveTimeout: const Duration(seconds: 30),
  );

  final dio = Dio(baseOptions);

  final Options requestOptions = Options(
    method: 'post',
    headers: {},
    contentType: Headers.multipartFormDataContentType,
  );

  dio.httpClientAdapter = IOHttpClientAdapter(
    createHttpClient: () {
      final HttpClient client =
          HttpClient(context: SecurityContext(withTrustedRoots: false));
      client.badCertificateCallback = (cert, host, port) => true;
      return client;
    },
  );

  await dio.request(
    "/upload_file",
    queryParameters: {},
    data: formData,
    options: requestOptions,
    onSendProgress: (received, total) {
      if (total > 0) {
        final progress = (received / total) * 100;
        print('${progress.toStringAsFixed(0)}% uploaded');
      }
    },
    cancelToken: CancelToken(),
  );

  return Result(data: true);
}

Expected Result

Success execute API call with uploaded files/images

Actual Result

Received DioException error