How to Pick Multiple Image And Upload it via RestAPI Flutter

To pick images from the library use a package from pub.dev. For example multi_image_picker for example.

The question of uploading multiple images to Dio is a duplicate. But here is the suggested solution in the linked article:

Future<Response<dynamic>> uploadImages(List<Asset> images, String url) async {
  List<MultipartFile> multipartImageList = new List<MultipartFile>();

  for (Asset asset in images) {
    ByteData byteData = await asset.getByteData();
    List<int> imageData = byteData.buffer.asUint8List();
    MultipartFile multipartFile = new MultipartFile.fromBytes(
      imageData,
      filename: 'load_image',
      contentType: MediaType("image", "jpg"),
    );
    multipartImageList.add(multipartFile);
  }

  FormData formData = FormData.fromMap({
    "multipartFiles": multipartImageList,
    "userId": '1'
  });

  Dio dio = new Dio();
  var response = await dio.post(url, data: formData);
  return response;
}