Question

我有一个小部件（SessionManager），当有新的流对象可用但不重绘时，我希望对其进行重绘，包括其子级。我按下一个按钮来获取下一个问题，如果我遇到一个问题，我应该进入一个新视图，但我不能超越该按钮视图。

class SessionManager extends StatelessWidget{

  @override
  Widget build(BuildContext context) {

    return StreamProvider<Question>.value(
      value: QuizzService().questionStream,
      child: MaterialApp(
          home: Wrapper()
      )
    );

  }
}

class Wrapper extends StatelessWidget{

  @override
  Widget build(BuildContext context) {
      final Question question = Provider.of<Question>(context, listen: true);

      if(question != null){
        return SingleAnswerWithImage();
      }else{
        return
          RaisedButton(
            child: Text("Start question"),
            onPressed: () {
              QuizzService().getNextQuestion();
            },

          );
      }
  }
}

class QuizzService {
  StreamController<Question> _questionStreamController = StreamController();

  Stream<Question> get questionStream {
    return _questionStreamController.stream;
  }

  void getNextQuestion() {

    List<String> answerOptions = ["Hell yes!", "Hell no!", "Why would you even ask me that", "Some answers can be to long as well i guess. This is probably one of them. Unless there is some magic in flutter that autoscales extremly long long texts"];

    Question q = new Question("How do you know hello world? " + TimeOfDay.now().toString(), "https://picsum.photos/370/250", answerOptions, "Java - core", QuestionType.SingleAnswerWithImage);

    _questionStreamController.add(q);

  }

class Question {

  String text;
  String imageUrl;
  List<String> answerOptions;
  String tag;
  QuestionType type;


  Question(this.text, this.imageUrl, this.answerOptions, this.tag, this.type);

}

Answer 1

我的问题是我在不同的小部件中有多个QuizzService类的实例。因此解决方案是使QuizzService类成为单例。这是我的QuizzService的最终版本

class QuizzService {
  StreamController<Question> _questionStreamController = StreamController();

  static final QuizzService _singleton = new QuizzService._internal()

  Stream<Question> get questionStream {
    return _questionStreamController.stream;
  }

  factory QuizzService() {
    return _singleton;
  }

  QuizzService._internal() {

  }

  void getNextQuestion() {

    List<String> answerOptions = ["Hell yes!", "Hell no!", "Why would you even ask me that", "Some answers can be to long as well i guess. This is probably one of them. Unless there is some magic in flutter that autoscales extremly long long texts"];

    Question q = new Question("How do you know hello world? " + TimeOfDay.now().toString(), "https://picsum.photos/370/250", answerOptions, "Java - core", QuestionType.SingleAnswerWithImage);

    _questionStreamController.add(q);

  }
}

Flutter StreamProvider没有更新

1 个答案: