attempted some StackOverflow fixes but none worked[Error Image](https://i.sstatic.net/ogEfH.jpg)
I also change everything that needed a null check to nullsafety
class QuestionnaireScreen extends StatefulWidget {
final Questionnaire questionnaire;
QuestionnaireScreen({required this.questionnaire});
@override
_QuestionnaireScreenState createState() => _QuestionnaireScreenState();
}
class _QuestionnaireScreenState extends State<QuestionnaireScreen> {
List<Question> get questions => widget.questionnaire.questions;
late int questionIndex;
Question get currentQuestion => questions[questionIndex];
int get numberOfQuestions => questions.length;
late List<int> chosenAnswers;
bool get userHasAnsweredCurrentQuestion =>
chosenAnswers[questionIndex] != null;
String get instructions => widget.questionnaire.instructions;
String getResultInterpretation() {
// calculate user's total score
int result = 0;
for (int index = 0; index < numberOfQuestions; index++) {
Question question = questions[index];
int answerIndex = chosenAnswers[index];
Answer answer = question.answers[answerIndex];
int score = answer.score;
result += score;
}
// determine interpretation for result
List<Interpretation> interpretations = widget.questionnaire.interpretations;
for (Interpretation interpretation in interpretations) {
if (result >= interpretation.score) {
return interpretation.text;
}
}
// if something went wrong, return the worst interpretation
return interpretations.last.text;
}
@override
void initState() {
super.initState();
questionIndex = 0;
//THIS IS TH ELING CAUSING ISSUES
// STARTS HERE
chosenAnswers = List<int>(numberOfQuestions);
// ENDS HERE
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.questionnaire.name),
),
body: SafeArea(
child: SingleChildScrollView(
child: Column(
children: [
Padding(
padding:
const EdgeInsets.only(left: 20.0, right: 20.0, top: 20.0),
child: Text(
instructions,
textAlign: TextAlign.justify,
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.w500,
color: Theme.of(context).colorScheme.secondary,
),
),
),
Padding(
padding: const EdgeInsets.all(15.0),
child: Card(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
SizedBox(
height: 16,
),
Center(
child: DotsIndicator(
dotsCount: numberOfQuestions,
position: int.parse(questionIndex.toString()),
decorator: DotsDecorator(
size: Size.square(15),
activeSize: Size(18, 18),
activeColor: Theme.of(context).primaryColor,
color: Theme.of(context).disabledColor,
),
),
),
SizedBox(
height: 24,
),
Padding(
padding: const EdgeInsets.only(left: 30.0, right: 8.0),
child: Text(
currentQuestion.text,
style: TextStyle(
fontSize: 20, fontWeight: FontWeight.w700),
textAlign: TextAlign.left,
),
),
SizedBox(
height: 24,
),
RadioButtonGroup(
activeColor: Theme.of(context).primaryColor,
labels: currentQuestion.answers
.map((answer) => answer.text)
.toList(),
onChange: (_, answerIndex) => setState(() {
chosenAnswers[questionIndex] = answerIndex;
}),
picked: !userHasAnsweredCurrentQuestion
? ""
: currentQuestion
.answers[chosenAnswers[questionIndex]].text,
),
SizedBox(
height: 20,
),
Padding(
padding: const EdgeInsets.only(bottom: 20.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Visibility(
visible: questionIndex != 0,
child: Button.accent(
buttonLabel: 'Back',
onPressed: () {
onBackButtonPressed();
},
),
),
Button.primary(
buttonLabel: 'Next',
onPressed: () {
userHasAnsweredCurrentQuestion
? onNextButtonPressed()
: null;
})
],
),
),
],
),
),
),
],
),
),
),
);
}
void onNextButtonPressed() {
if (questionIndex < numberOfQuestions - 1) {
setState(() {
questionIndex++;
});
} else {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (context) => ResultScreen(
questionnaireName: widget.questionnaire.name,
interpretation: getResultInterpretation(),
),
),
);
}
}
void onBackButtonPressed() {
if (questionIndex > 0) {
setState(() {
questionIndex--;
});
}
}
}
Line of code throwing error
chosenAnswers = List<int>(numberOfQuestions);
Fixed Attempted
Tried changeing the error line to
chosenAnswers = numberOfQuestions as List<int>;
But didn't work either
Please who can this be fixed..?
I will appreciate help from everybody Output error
To initialize a list of length numberOfQuestions you can write
chosenAnswers = List.generate(numberOfQuestions, (index) => 0);
Which will initialize it with the value 0 on all indices. Although judging from
bool get userHasAnsweredCurrentQuestion =>
chosenAnswers[questionIndex] != null;
you would want a list of nullable ints, so
late List<int> chosenAnswers;
needs to be
late List<int?> chosenAnswers;
and then you should initiate it as
chosenAnswers = List.generate(numberOfQuestions, (index) => null);