如何管理 listview.builder 中的控制器列表，这取决于 listView.builder 用于迭代的不同列表

Question

image

I have list of objects (Question). I'm iterating over inside ListView.builder.

I have another list of objects (QuizQuestion) which from every QuizQuestion object I need a propery (ueserAnswer) for the user to change (that's why the TextFormField) so I can save and work with after that.

My main problem is the controller of textFormField and how to get the value.

This code results in 5 objects of Question under everyone a TextFormField (which is the userAnswer related to that exact question) what should I do in order to get the controller and value to work with after that.

At this stage, when I enter a value in any TextFormField and press on the button , I get this error Unhandled Exception: type 'Null' is not a subtype of type 'List<TextEditingController>' of 'function result' which is pointing to this line

for (var i=0;i<GlobalParams.quizmodel.quizQuestions.length;i++){
              print({controllers[i].text});
            }

Any help is REALLY appreciated image

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

  @override
  State<AnswerQuizPage> createState() => _AnswerQuizPageState();
}

class _AnswerQuizPageState extends State<AnswerQuizPage> {
  int? _numPages ;
  int _currentPage = 1;
  bool test=false;
  var questionController= QuestionController(QuestionRepositoryImpl());
  //List<String> reponse=[];
  List<String> asnwers=[];
  List<TextEditingController>_reponse=[];
  List<TextEditingController> _controllers = [];
   late List<TextEditingController> controllers;
  late List<String> reponse;
  List<QuestionModel> listofquestion=[];
  List<QuizQuestion> listofquizquestionsforquiz=GlobalParams.quizmodel.quizQuestions;
  @override
  List<dynamic> trList=[];
  GlobalKey<FormState> globalFormKey=GlobalKey<FormState>();
  void show(){
    List<TextEditingController> _controllers2=[];
    String test;
    GlobalParams.quizmodel.quizQuestions.forEach((element) { final   quantityController =
    TextEditingController(text: element.userAnswer);
    controllers.add(quantityController);
    });
   /* for (var  i=0; i<listofquizquestionsforquiz.length;i++){
      TextEditingController text3ess;
      setState(() {
        //text3ess.text=listofquizquestionsforquiz[i].userAnswer;
       // _controllers2[i].text=test;
      });
    }*/
setState(() {
  _controllers2=controllers;
});

  }
  void initState(){
    super.initState();
    //controllers=[];
show();
  }
  @override
  Widget build(BuildContext context) {
    print(GlobalParams.quizmodel.id);
    Future<List<QuestionModel>> quizlist=questionController.getQuestionsByQuizId(GlobalParams.quizmodel.id);
    quizlist.then((value)  {
      //_numPages=value.length-2;
      listofquestion=value;
    });
    /*if (GlobalParams.model.name=="essai"){
      Future<List<QuestionModel>> quizlist=questionController.getQuestionsByQuizId(1);
      quizlist.then((value)  {
        //_numPages=value.length-2;
        listofquestion=value;
      });
    }
    if (GlobalParams.model.name=="spiderman concentration quiz"){
      Future<List<QuestionModel>> quizlist=questionController.getQuestionsByQuizId(2);
      quizlist.then((value)  {
        //_numPages=value.length-2;
        listofquestion=value;
      });
    }*/
   /* Future<List<QuestionModel>> quizlist=questionController.getQuestionsByQuizId(GlobalParams.quizmodel.id);
    quizlist.then((value)  {
      //_numPages=value.length-2;
      listofquestion=value;
    });*/
    _numPages=listofquestion.length;
    //print(listofquestion);
    int? idtochoose;
    return Scaffold(
      appBar:AppBar(
        elevation: 0,
        title:Text('répondre au quiz'),
        actions: <Widget>[
          //login
          Container(

            decoration: BoxDecoration(
              //color: Colors.orange[600],
                borderRadius: BorderRadius.circular(10)),
            margin: EdgeInsets.only(right: 15.0, top:5.0, bottom: 5.0,),
            child: Tooltip(
              message: "vous devez finir le quiz",
              child: Icon(Icons.more_horiz),
            ),
            /*IconButton(
              icon: const Icon(Icons.arrow_back),
              //padding: EdgeInsets.fromLTRB(0, auto, auto, bottom)
              tooltip: 'Show Snackbar',
              onPressed: () {
                Navigator.of(context).pop();
                Navigator.pushNamed(context, "/superadminhomepage");
              },
            ),*/
          ),


        ],

      ),
      body: Container(
        margin: EdgeInsets.all(50),
        child: FutureBuilder<List<QuestionModel>>(
    future:questionController.getQuestionsByQuizId(GlobalParams.quizmodel.id),
    builder:(context ,snapshot){
    if(snapshot.connectionState==ConnectionState.waiting){
    return Center(child: CircularProgressIndicator(),);
    }
    if (snapshot.hasError){
    print('${snapshot.error}');
    print('${snapshot}');

    return Center(child: Text('${snapshot}'),);
    }
    return Column(
      children: [
        Expanded(child: buildBodyContent(snapshot, questionController)),
       /* QuizQuestionTextControllerWidget(controllers: _controllers, listofquizquestions: GlobalParams.quizmodel.quizQuestions, reponse: reponse),*/
        SizedBox(height: 50,),
        Container(
          child: FormHelper.submitButton("Ajouter", () async{


            print('hello');
            print('${GlobalParams.quizmodel.id}');
            print('${GlobalParams.quizmodel.quizQuestions[0].quizquestionpk.idQuestion}');
            /*for (var i=0;i<listofquizquestionsforquiz.length;i++){
              print("thabbet");
              print('réponse melowel ${ GlobalParams.quizmodel.quizQuestions[i].userAnswer}');
              print ("chouf");
            }*/
            /*for (var j=0;j<_controllers.length;j++){
              print('${_controllers[j].text}');
            }*/
            for (var j=0;j<reponse.length;j++){
              print('${reponse[j]}');
            }
         /*   for (TextEditingController c in _controllers) {c.dispose();}*/
            for (var i=0;i<GlobalParams.quizmodel.quizQuestions.length;i++){
              print({controllers[i].text});
            }
            print(controllers[0].text);
          },
            btnColor: Colors.blue,
            borderColor: Colors.white,
            txtColor: Colors.white,
            borderRadius: 10,),
        ),

      ],
    );

    },
    ),
      ),
    );
  }
}

SafeArea buildBodyContent (AsyncSnapshot <List<QuestionModel>> snapshot,
    QuestionController questionController){
 List <String> reponse=[];
  List<String> asnwers=[];
 List<QuizQuestion> listofquizquestions=GlobalParams.quizmodel.quizQuestions;
 List<TextEditingController> controllers=[];
 // List<TextEditingController> _reponse=[];
  List<TextEditingController> _controllers = [];
 int idx;

 GlobalParams.quizmodel.quizQuestions.forEach((element) { final   quantityController =
 TextEditingController(text: element.userAnswer);
 controllers.add(quantityController);
 });
  return SafeArea(
    child:
    Scrollbar(
      isAlwaysShown: true,
      thickness: 5,
     // scrollbarOrientation: ScrollbarOrientation.,
      child: ListView.builder(
          itemBuilder: (context,index)
          {
         //   _controllers.add(new TextEditingController());
            var cq=snapshot.data?[index];
            controllers.add( TextEditingController());
            listofquizquestions.map((e) { idx = listofquizquestions.indexOf(e);
            controllers.add( TextEditingController());
            } );

            return Column(
              children:[
                SizedBox(height: 10,),
                Container(
                  width: MediaQuery.of(context).size.width/2,
                  padding: EdgeInsets.only(top:5.0, bottom: 5.0, left: 10.0, right: 10.0),
                  decoration: BoxDecoration(
                    color: Colors.orange,
                    borderRadius: BorderRadius.all(Radius.circular(10)),
                  ),
                  child: Column(
                    children: [
                      SizedBox(height: 10,),
                      Text(cq!.enonce, style: TextStyle(
                        fontSize: 16,

                      ),
                      ),
                      SizedBox(height: 10,),
                      Text(
                        'réponse a : ${cq.propositionA}', style: TextStyle(
                        fontSize: 16,

                      ),),
                      SizedBox(height: 10,),
                      Text(
                        'réponse b : ${cq.propositionB}', style: TextStyle(
                        fontSize: 16,

                      ),),
                      SizedBox(height: 10,),
                      Text(
                        'réponse c : ${cq.propositionC}', style: TextStyle(
                        fontSize: 16,

                      ),),
                      SizedBox(height: 10,),
                      Text(
                        'réponse d : ${cq.propositionD}', style: TextStyle(
                        fontSize: 16,

                      ),),
                      SizedBox(height: 10,),

                    ],
                  ),
                ),
                SizedBox(height: 10,),
                /*TextFormField(
                  controller: _controllers[index],

                  onEditingComplete:(){ print(""); },
                  decoration: InputDecoration(
                    hintText: "nom du quiz",
                  ),
                  validator: (value){
                    setState(){

                    }
                    value="a";
                    if (value.isNotEmpty){
                     // _controllers.add(_controllers[index]);
                      print('${_controllers[index]}');
                      reponse[index]=value;
                      //asnwers.add(asnwers[index]);
                      // tr="QUATRE_A_CINQ";
                      return null;
                    } else {
                      return "libelle ne peut pas être vide";
                    }
                  },
                  keyboardType: TextInputType.text,
                ),*/
                /*Column(
                  // mainAxisSize : MainAxisSize.min,
                  children:[
                    ...(listofquizquestions).map((item) {
                      int idx = listofquizquestions.indexOf(item);
                      controllers.add(TextEditingController());
                      var j=0;
                      return  */
                        Column(
                          children: [
                            TextFormField(
                            controller: controllers[index],
                            //onEditingComplete: (text) {  print('First text field: $text');  },
                            decoration: InputDecoration(
                              hintText: ' réponse',
                            ),
                            validator: (value){
                              value="a";
                              if (value.isNotEmpty){
                                // _controllers.add(_controllers[index]);
                                print('${controllers[index].text}');
                                reponse.add(value);
                                //asnwers.add(asnwers[index]);
                                // tr="QUATRE_A_CINQ";
                                return null;
                              } else {
                                return "libelle ne peut pas être vide";
                              }
                            },
                            keyboardType: TextInputType.text,
                      ),
                          ],
                        ),
                   /* })
                  ],
                ),*/
                SizedBox(height: 10,),
              ],
            );
          },
          itemCount: snapshot.data?.length ??0),
    ),
  );
}

Answer 1

For solving this error: Unhandled Exception: type 'Null' is not a subtype of type 'List<TextEditingController>' of 'function result'

Try writing this:

List<TextEditingController> controllers = [];

instead of:

late List<TextEditingController> controllers;