flutter_bloc - 如果没有 BlocBuilder，我如何获得价值？

Question

我仍然是流和 bloc 模式的初学者。

我想做以下事情：

• 触发事件。
• 根据事件获取对象的状态
• 将此对象作为 JSON 存储在数据库中。

所有示例都在展示，如何使用 BlocBuilder 在小部件中显示对象。但我不需要显示值，只获取并存储它。我不知道如何将值放入变量中。

我该怎么做？在 View 类中，我正在调度事件，但现在我需要知道如何在不使用 BlocBuilder 的情况下将对象恢复为状态。

以下是详细信息：

集团

class SchoolBloc extends Bloc<SchoolEvent, SchoolState> {
  final SchoolRepository _schoolRepository;
  StreamSubscription _schoolSubscription;

  SchoolBloc({@required SchoolRepository schoolRepository})
      : assert(schoolRepository != null),
        _schoolRepository = schoolRepository;

  @override
  SchoolState get initialState => SchoolsLoading();

  @override
  Stream<SchoolState> mapEventToState(SchoolEvent event) async* {
    if (event is LoadSchool) {
      yield* _mapLoadSchoolToState();

  Stream<SchoolState> _mapLoadSchoolToState(LoadSchool event) async* {
    _schoolSubscription?.cancel();
    _schoolSubscription = _schoolRepository.school(event.id).listen(
      (school) {
        SchoolLoaded(school);
      }
    );
  }

活动

@immutable
abstract class SchoolEvent extends Equatable {
  SchoolEvent([List props = const []]) : super(props);
}
class LoadSchool extends SchoolEvent {
  final String id;

  LoadSchool(this.id) : super([id]);

  @override
  String toString() => 'LoadSchool';
}

州

@immutable
abstract class SchoolState extends Equatable {
  SchoolState([List props = const []]) : super(props);
}

class SchoolLoaded extends SchoolState {
  final School school;

  SchoolLoaded([this.school]) : super([school]);

  @override
  String toString() => 'SchoolLoaded { school: $school}';
}

查看

class CourseView extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _CourseViewState();
}

class _CourseViewState extends State<CourseView> {
  @override
  initState() {
    super.initState();
    print("this is my init text");

    final _schoolBloc = BlocProvider.of<SchoolBloc>(context);

    _schoolBloc.dispatch(LoadSchool("3kRHuyk20UggHwm4wrUI"));

    // Here I want to get back the school object and save it to a db
  }

测试失败

出于测试目的，我做了以下操作：

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:teach_mob/core/blocs/school/school.dart';

class CourseView extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _CourseViewState();
}

class _CourseViewState extends State<CourseView> {

  @override
  void initState() {
    super.initState();  
        BlocProvider.of<SchoolBloc>(context)
      .dispatch(LoadSchool("3kRHuyk20UggHwm4wrUI"));  
  }

  @override
  Widget build(BuildContext context) {
    return BlocListener<SchoolBloc, SchoolState>(
      listener: (context, state) {
        print("BlocListener is triggered");
      },
      child: Text("This is a test")
    );
  }
}

LoadSchool 事件被触发。 BlocListener的child属性中的文本显示出来了，但是应该打印“BlocListener is triggered”的监听函数没有被执行。

Answer 1

使用 BlocListener。它旨在用于您提到的那些情况。