Unhandled Exception: type 'Null' is not a subtype of type 'int' in type cast error when trying to call function with no int

Hello I was calling a startelection function from my flutter app on a button click and I got this error the startelection function connects my flutter app with my solidity smart contract and starts the election through infura I don't know why I am getting this error it was running fine before

error :

E/flutter (31094): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: type 'Null' is not a subtype of type 'int' in type cast
E/flutter (31094): #0 JsonRPC.call (package:web3dart/json_rpc.dart:53:27)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #1 Web3Client._makeRPCCall (package:web3dart/src/core/client.dart:54:20)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #2 Web3Client.getGasPrice (package:web3dart/src/core/client.dart:175:18)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #3 _fillMissingData (package:web3dart/src/core/transaction_signer.dart:36:16)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #4 Web3Client.signTransaction (package:web3dart/src/core/client.dart:316:26)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #5 Web3Client.sendTransaction (package:web3dart/src/core/client.dart:285:18)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #6 startElection (package:election/services/functions.dart:29:18)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094): #7 _HomeState.build.<anonymous closure> (package:election/pages/home.dart:53:25)
E/flutter (31094): <asynchronous suspension>
E/flutter (31094):

home.dart
`
import 'package:election/utils/Constants.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart';
import 'package:web3dart/web3dart.dart';

import '../services/functions.dart';
import 'Electioninfo.dart';

class Home extends StatefulWidget {
const Home({Key? key}) : super(key: key);

@override
State createState() => _HomeState();
}

class _HomeState extends State {
late Client? httpClient;
late Web3Client? ethclient;
TextEditingController controller = TextEditingController();

@override
void initState() {
httpClient = Client();
ethclient = Web3Client(infura_url, httpClient!);
super.initState();
}

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Start Election'),
),
body: Container(
padding: const EdgeInsets.all(14),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
TextField(
controller: controller,
decoration: const InputDecoration(
filled: true, hintText: 'Enter election name'),
),
const SizedBox(
height: 10,
),
Container(
width: double.infinity,
height: 45,
child: ElevatedButton(
onPressed: () async {
if (controller.text.isNotEmpty) {
await startElection(controller.text, ethclient!);
if(!mounted)return;
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ElectionInfo(
ethClient: ethclient!,
electionName: controller.text,
)));
}
},
child: const Text('Start Election')))
],
),
),
);
}
}`

functions.dart:

`Future startElection(String name,Web3Client ethclient) async{

var response = await callFunction('startElection', [name], ethclient, owner_private_key);
print("election started successfully");

return response;
}

Future callFunction(String funcname,Listargs,Web3Client ethClient,String privateKey) async{

EthPrivateKey credentials = EthPrivateKey.fromHex(privateKey);
DeployedContract contract = await loadcontract();

final ethfunction = contract.function(funcname);
final result = ethClient.sendTransaction(
credentials,Transaction.callContract(contract: contract, function: ethfunction, parameters: args),
chainId: null,fetchChainIdFromNetworkId: true);

return result;
}`

Comments

[Ayevbeosa Iyamu]

Most likely the JSON response isn't what the JSON parser was expecting.