当我回来或完成时如何重置我的控制器？

分类：编程问答

如何解决当我回来或完成时如何重置我的控制器？

enter image description here

我有一个 QuestionController 类 extends GetxController

当我使用控件退出页面时，我希望它停止工作（因为它仍在后台运行）并在我返回该页面时重新启动。

我已经尝试过：我在 ScoreScreen() 的路线之后添加了这些（在 nextQuestion () 中）：

_isAnswered = false;
_questionNumber.value = 1;

我在进入分数页面之前重置了数值。如果您转到分数页面，它可能会起作用，但是如果您早点回来，则不会。 （问题 num/4 在这里不起作用）。所以这种方式不适合。

当页面退出时，我可以通过什么方式停止并重置它？

控制器类代码：

class QuestionController extends GetxController
    with SingleGetTickerProviderMixin {
  PageController _pageController;

  PageController get pageController => this._pageController;

  List<Question> _questions = questions_data
      .map(
        (e) => Question(
            id: e["id"],question: e["question"],options: e["options"],answer: e["answer_index"]),)
      .toList();

  List<Question> get questions => this._questions;

  bool _isAnswered = false;

  bool get isAnswered => this._isAnswered;

  int _correctAns;

  int get correctAns => this._correctAns;

  int _selectedAns;

  int get selectedAns => this._selectedAns;

  RxInt _questionNumber = 1.obs;

  RxInt get questionNumber => this._questionNumber;

  int _numOfCorrectAns = 0;

  int get numOfCorrectAns => this._numOfCorrectAns;

  @override
  void onInit() {
    _pageController = PageController();
    super.onInit();
  }

  @override
  void onClose() {
    super.onClose();
    _pageController.dispose();
  }

  void checkAns(Question question,int selectedIndex) {
    _isAnswered = true;
    _correctAns = question.answer;
    _selectedAns = selectedIndex;

    if (_correctAns == _selectedAns) _numOfCorrectAns++;

    update();

    Future.delayed(Duration(seconds: 2),() {
      nextQuestion();
    });
  }

  void nextQuestion() {
    if (_questionNumber.value != _questions.length) {
      _isAnswered = false;
      _pageController.nextPage(
          duration: Duration(milliseconds: 300),curve: Curves.ease);
    } else {
      Get.off(ScoreScreen(correctNum: _numOfCorrectAns)); // GetMaterialApp()

      // _isAnswered = false;

      _numOfCorrectAns = 0;

      //_questionNumber.value = 1;

    }
  }

  void updateTheQuestionNum(int index) {
    _questionNumber.value = index + 1;
  }
}

完整代码如下

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:get/get.dart';  // get: ^3.25.4

//  QuizPage()     ===============> 50. line      (Question 1/4) 81. line
//  QuestionCard()  ==============> 116. line
//  Option()   ===================> 163. line
//  QuestionController()  ========> 218. line
//  ScoreScreen() ================> 345. line

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      debugShowCheckedModeBanner: false,theme: ThemeData(canvasColor: Colors.blue),home: HomeScreen(),);
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Home Page"),),body: Center(
        child: InkWell(
          onTap: () {
            Navigator.push(
                context,MaterialPageRoute(builder: (context) => QuizPage()));
          },child: Container(
            padding: EdgeInsets.all(22),color: Colors.green,child: Text(
              "Go Quiz Page",style: TextStyle(color: Colors.white),);
  }
}

class QuizPage extends StatelessWidget {
  const QuizPage({
    Key key,}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    QuestionController _questionController = Get.put(QuestionController());

    return Scaffold(
      appBar: AppBar(
        title: Text("Quiz Page"),body: Stack(
        children: [
          SafeArea(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,children: [
                SizedBox(
                  height: 16,Padding(
                  padding: EdgeInsets.symmetric(horizontal: 16),child: Obx(
                    () => Center(
                      child: RichText(
                          text: TextSpan(
                              // text,style default adjust here OR:children[TextSpan(1,adjust 1),TextSpan(2,adjust 2),..]
                              text:
                                  "Question ${_questionController._questionNumber.value}",style: TextStyle(
                                  fontSize: 33,color: Colors.white70),children: [
                            TextSpan(
                                text:
                                    "/${_questionController._questions.length}",style: TextStyle(fontSize: 25))
                          ])),Divider(color: Colors.white70,thickness: 1),SizedBox(
                  height: 16,Expanded(
                  child: PageView.builder(
                    physics: NeverScrollableScrollPhysics(),controller: _questionController._pageController,onPageChanged: _questionController.updateTheQuestionNum,itemCount: _questionController.questions.length,itemBuilder: (context,index) => QuestionCard(
                      question: _questionController.questions[index],)
              ],)
        ],);
  }
}

class QuestionCard extends StatelessWidget {
  final Question question;

  const QuestionCard({
    Key key,@required this.question,}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    QuestionController _controller = Get.put(QuestionController());

    return Container(
      margin: EdgeInsets.only(left: 16,right: 16,bottom: 16),padding: EdgeInsets.all(16),decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(25),color: Colors.white,child: Column(
        children: [
          Text(
            question.question,style: TextStyle(fontSize: 22),SizedBox(
            height: 8,Flexible(
            child: SingleChildScrollView(
              child: Column(
                children: [
                  ...List.generate(
                      question.options.length,(index) => Option(
                          text: question.options[index],index: index,press: () => _controller.checkAns(question,index)))
                ],);
  }
}

class Option extends StatelessWidget {
  final String text;
  final int index;
  final VoidCallback press;

  const Option({
    Key key,@required this.text,@required this.index,@required this.press,}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return GetBuilder<QuestionController>(
        init: QuestionController(),builder: (q) {
          Color getRightColor() {
            if (q.isAnswered) {
              if (index == q._correctAns) {
                return Colors.green;
              } else if (index == q.selectedAns &&
                  q.selectedAns != q.correctAns) {
                return Colors.red;
              }
            }
            return Colors.blue;
          }

          return InkWell(
            onTap: press,child: Container(
              //-- Option
              margin: EdgeInsets.only(top: 16),decoration: BoxDecoration(
                  color: getRightColor(),borderRadius: BorderRadius.circular(16)),child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,children: [
                  Text(
                    "${index + 1}. $text",style: TextStyle(fontSize: 16,color: Colors.white),],);
        });
  }
}

class QuestionController extends GetxController
    with SingleGetTickerProviderMixin {
  PageController _pageController;

  PageController get pageController => this._pageController;

  List<Question> _questions = questions_data
      .map(
        (e) => Question(
            id: e["id"],)
      .toList();

  List<Question> get questions => this._questions;

  bool _isAnswered = false;

  bool get isAnswered => this._isAnswered;

  int _correctAns;

  int get correctAns => this._correctAns;

  int _selectedAns;

  int get selectedAns => this._selectedAns;

  RxInt _questionNumber = 1.obs;

  RxInt get questionNumber => this._questionNumber;

  int _numOfCorrectAns = 0;

  int get numOfCorrectAns => this._numOfCorrectAns;

  @override
  void onInit() {
    _pageController = PageController();
    //_pageController.addListener(() { _questionNumber.value = _pageController.page.round()+1; });
    super.onInit();
  }

  @override
  void onClose() {
    super.onClose();
    _pageController.dispose();
  }

  void checkAns(Question question,curve: Curves.ease);
    } else {
      Get.off(ScoreScreen(correctNum: _numOfCorrectAns)); // GetMaterialApp()

      // _isAnswered = false;

      _numOfCorrectAns = 0;

      //_questionNumber.value = 1;

    }
  }

  void updateTheQuestionNum(int index) {
    _questionNumber.value = index + 1;
  }
}

class Question {
  final int id,answer;
  final String question;
  final List<String> options;

  Question({
    @required this.id,@required this.options,@required this.answer,});
}

const List questions_data = [
  {
    "id": 1,"question": "Question 1","options": ['option A','B','C','D'],"answer_index": 3,},{
    "id": 2,"question": "Question 2","answer_index": 2,{
    "id": 3,"question": "Question 3","answer_index": 0,{
    "id": 4,"question": "Question 4",];

class ScoreScreen extends StatelessWidget {
  final int correctNum;

  ScoreScreen({@required this.correctNum});

  @override
  Widget build(BuildContext context) {
    QuestionController _qController = Get.put(QuestionController());

    return Scaffold(
      body: Stack(
        fit: StackFit.expand,children: [
          Column(
            children: [
              Spacer(
                flex: 2,Text(
                "Score",style: TextStyle(fontSize: 55,Spacer(),Text(
                "${correctNum * 10}/${_qController.questions.length * 10}",style: TextStyle(fontSize: 33,Spacer(
                flex: 2,InkWell(
                onTap: () => Get.back(),borderRadius: BorderRadius.circular(16),child: Container(
                  padding: EdgeInsets.all(16),decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(16),color: Colors.white24),child: Text(
                    "Back to Home Page",);
  }
}

解决方法

更新答案：

好的，在看到您的完整代码后，我的解决方案需要几个额外的步骤。

将此添加到您的控制器类。它需要在您的 HomeScreen

的 onPressed 中调用 
 void resetQuestionNumber() => _questionNumber.value = 1;

您必须提前初始化控制器，以便将其添加到您的 HomeScreen

final _questionController = Get.put(QuestionController());

您的 onTap 的 HomeScreen 现在看起来像这样。

onTap: () {
    _questionController.resetQuestionNumber();
    Navigator.push(
    context,MaterialPageRoute(builder: (context) => QuizPage()));
},

应该可以。 _pageController 索引直到问题得到回答后才会更新，因此只需在转到 _questionNumber 之前重置 QuizPage，然后它就会赶上。您的 updateTheQuestionNum 可以完全消失，您无需再在 onPageChanged 的 PageView.builder 中处理任何此类事情。

原答案：

如果您只是想让 RxInt _questionNumber 与 _pageController 的值相匹配，您可以在 onInit 中添加一个监听器

_pageController.addListener(() {
  _questionNumber.value = _pageController.page.round() + 1;
});

编辑：添加 + 1 以说明从 0 开始的索引

,

你可以监听“onBack 事件”并配置控制器 这是一个例子

@override
Widget build(BuildContext context) {
  return WillPopScope(
    onWillPop: () {
      disposeController(context);
    },child: Scaffold(
      key: _scaffoldKey,appBar: AppBar(
        leading: IconButton(
            icon: Icon(Icons.arrow_back),onPressed: () {
              _moveToSignInScreen(context);
            }),title: Text("Profile"),),);

}

void disposeController(BuildContext context){
//or what you wnat to dispose/clear
 _pageController.dispose()
}
,

如果你只有一个控制器，你可以使用 Get.reset()。它会清除所有注册的实例。

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