Flutter : Multipart File request not working - api

Question

I want to upload image by multipart File request. With using this code When I pass two image files then it's working fine. But when I want to pass one image file and another is null then it's not working.
where is the problem? How can I solve this ?
Here is my code -
Future<Map<String, dynamic>> updateprofile(
UpdateProfileInfo updateProfileInfo,
File imageFile,
File signatureFile) async {
String url = "$baseAPIUrl/update-profile-info";
String _token = await SavedData().loadToken();
String authorization = "Bearer $_token";
final headers = {
'Content-Type': 'application/json',
'Accept': 'application/json',
"Authorization": authorization
};
var request = http.MultipartRequest("POST", Uri.parse(url));
request.headers.addAll(headers);
request.fields.addAll(updateProfileInfo.toJson());
request.files
.add(await http.MultipartFile.fromPath('image', imageFile.path));
request.files.add(
await http.MultipartFile.fromPath('signature', signatureFile.path));
print(" Update Profile Json ${updateProfileInfo.toJson()}");
print("Request Fields ${request.fields}");
http.StreamedResponse response = await request.send();
String respStr = await response.stream.bytesToString();
dynamic respJson;
try {
respJson = jsonDecode(respStr);
} on FormatException catch (e) {
print(e.toString());
}
print('API ${response.statusCode}\n $respJson');
bool isSuccess = response.statusCode == 200;
var data = json.decode(respStr);
return {
'isSuccess': isSuccess,
"message": isSuccess ? data["success"]["message"] : null,
"name": isSuccess ? data["success"]["name"] : null,
"classgroup": isSuccess ? data["success"]["classgroup"] : null,
"image": isSuccess ? data["success"]["image"] : null,
"error": isSuccess ? null : data['error']['message'],
};
}
Here is postman Screenshot
1.
2. POSTMAN Generated code for Dart - http

Answer 1

when one of your file is null, you should avoid adding it to the request body.
if(imageFile != null){
request.files
.add(await http.MultipartFile.fromPath('image', imageFile.path));
}
if(signatureFile != null){
request.files.add(
await http.MultipartFile.fromPath('signature', signatureFile.path));
}
its because signatureFile.path is going to cause an error here

Answer 2

using dio package should work
Future<bool> updateImage(var pickedFile) async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();` <br/>
var token = sharedPreferences.getString("token");
Dio dio = Dio();
final File file = File(pickedFile.path);
String fileName = file.path.split('/').last;
dio.options.headers["authorization"] = token;
FormData formData = FormData.fromMap({
"image": await MultipartFile.fromFile(file.path),
});
try {
var response = await dio.post(API.kBASE_URL, data: formData);
if (response.statusCode == 200) {
return true;
} else {
return false;
}
} catch (r) {
return false;
}
}