The getter '_controller' was called on null. Flutter - flutter

Question

I'm using this package in Flutter: https://pub.dev/packages/circular_countdown_timer
However, I need to create a separate widget to separate my code a little bit. I created something like this:
import 'package:circular_countdown_timer/circular_countdown_timer.dart';
import 'package:flutter/material.dart';
class CustomOtpCard extends StatefulWidget {
final String duration;
final String accountName;
final String otp;
final Function(CountDownController) onComplete;
CustomOtpCard({
#required this.duration,
#required this.accountName,
#required this.otp,
#required this.onComplete,
});
#override
_CustomOtpCardState createState() => _CustomOtpCardState();
}
class _CustomOtpCardState extends State<CustomOtpCard> {
CountDownController _controller = CountDownController();
#override
Widget build(BuildContext context) {
return Card(
child: ListTile(
leading: CircularCountDownTimer(
duration: int.parse(widget.duration),
onComplete: widget.onComplete(_controller),
initialDuration: 0,
ringColor: Colors.grey[300],
fillColor: Colors.purple,
backgroundColor: Colors.purple[500],
width: 50.0,
height: 50.0,
),
title: Text(widget.accountName),
subtitle: Text(widget.otp),
),
);
}
}
Now, I use it like this:
return ListView.builder(
itemCount: _totpItems.length,
itemBuilder: (context, index) {
return CustomOtpCard(
duration: '30',
onComplete: (controller) {
BlocProvider.of<TotpGeneratorBloc>(context)
.add(GetTotpItemsEvent());
controller.restart();
},
accountName: _totpItems[index].accountName,
otp: _totpItems[index].otp,
);
},
);
Then the error shows up "The getter '_controller' was called on null.". Here's the image of my error:
It says, that the _controller I passed to the callback is null. What am I doing wrong? Can someone give me a hint?
Thanks!

Answer 1

I presume that when you call controller.restart(), _CustomOtpCardState has been disposed then _controller do not exist anymore.
You could do it this way :
First turn onComplete to a VoidCallback (equivalent to void Function()) :
final VoidCallback onComplete;
Then use it this way :
...
duration: int.parse(widget.duration),
onComplete: () {
widget.onComplete();
_controller.restart();
},
initialDuration: 0,
...
In your ListView.builder :
return CustomOtpCard(
duration: '30',
onComplete: () {
BlocProvider.of<TotpGeneratorBloc>(context)
.add(GetTotpItemsEvent());
},
accountName: _totpItems[index].accountName,
otp: _totpItems[index].otp,
);