State Management with Provider Use Provider to separte state from the parent widget

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Quiz State

Define a class that contains the data required by the UI. Add getters and setters for the data, making sure to call notifyListeners() when the data changes.

file_type_flutter quiz/quiz_state.dart
import 'package:flutter/material.dart';
import 'package:quizapp/services/models.dart';

class QuizState with ChangeNotifier {
  double _progress = 0;
  Option? _selected;

  double get progress => _progress;
  Option? get selected => _selected;

  set progress(double newValue) {
    _progress = newValue;
    notifyListeners();
  }

  set selected(Option? newValue) {
    _selected = newValue;
    notifyListeners();
  }
}

Provider

Now that we have our state, we need to make it available to widgets that depend on it. At this point, we also use a FutureBuilder to fetch the quiz data from Firestore.

file_type_flutter quiz/quiz_provider.dart
file_type_flutter quiz.dart
class QuizScreen extends StatelessWidget {
  const QuizScreen({Key? key, required this.quizId}) : super(key: key);
  final String quizId;

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => QuizState(),
      child: FutureBuilder<Quiz>(
        future: FirestoreService().getQuiz(quizId),
        builder: (context, snapshot) {
          var state = Provider.of<QuizState>(context);

          if (!snapshot.hasData || snapshot.hasError) {
            return Loader();
          } else {
            var quiz = snapshot.data!;

            return Scaffold();
          }
        },
      ),
    );
  }
}

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