如何让一个集团在全球范围内变得可访问

Question

我正在努力将块模式放入我的 Flutter 应用程序中。我使用这个库是为了让它对我来说更简单： https: //felangel.github.io/bloc/#/

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我有一个主要问题。如何让我的 Bloc 在全球范围内都可访问，而不需要一次又一次地传递下去？

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这是我的代码：

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主要.dart：

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import \'package:flutter/material.dart\';\nimport \'package:flutter_bloc/flutter_bloc.dart\';\n\nimport \'db_bloc.dart\';\nimport \'NotesPage.dart\';\n\nvoid main() => runApp(MyApp());\n\nclass MyApp extends StatefulWidget {\n  @override\n  State<StatefulWidget> createState() => MyAppState();\n}\n\nclass MyAppState extends State<MyApp> {\n  final DatabaseBloc _dbNoteBloc = DatabaseBloc();\n\n  @override\n  Widget build(BuildContext context) {\n    return MaterialApp(\n      title: \'Flutter Demo\',\n      home: BlocProvider<DatabaseBloc>(\n        bloc: _dbNoteBloc,\n        child: NotesPage(),\n      ),\n    );\n  }\n\n  @override\n  void dispose() {\n    _dbNoteBloc.dispose();\n    super.dispose();\n  }\n}\n

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注释页：

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import \'package:flutter/material.dart\';\nimport \'package:flutter_bloc/flutter_bloc.dart\';\n\nimport \'db_bloc.dart\';\nimport \'note_model.dart\';\n\nclass NotesPage extends StatefulWidget {\n  _NotesPageState createState() => _NotesPageState();\n}\n\nclass _NotesPageState extends State<NotesPage> {\n  @override\n  Widget build(BuildContext context) {\n    final DatabaseBloc _dbNoteBloc = BlocProvider.of<DatabaseBloc>(context);\n\n    return BlocBuilder<NoteDbEvent, List<Note>>(\n      bloc: _dbNoteBloc,\n      builder: (BuildContext context, List<Note> state) {\n        return Scaffold(\n          appBar: AppBar(\n            title: Text("bla"),\n            actions: <Widget>[\n              // action button\n              IconButton(\n                icon: Icon(Icons.refresh),\n                onPressed: () => _dbNoteBloc\n                    .dispatch(NoteDbEvent(type: NoteDbEventType.GetAll)),\n              ), // action button\n            ],\n          ),\n          body: ListView.builder(\n            itemCount: state.length,\n            itemBuilder: (BuildContext context, int index) {\n              return Column(\n                children: <Widget>[\n                  ListTile(\n                    title: Text(\'${state[index].title}\'),\n                    onLongPress: () => showDialog(\n                          context: context,\n                          builder: (BuildContext context) {\n                            return AlertDialog(\n                              title: Text("L\xc3\xb6schen"),\n                              content: Text(\n                                  "M\xc3\xb6chtest du diese Notiz wirklich l\xc3\xb6schen?"),\n                              actions: <Widget>[\n                                FlatButton(\n                                  child: Text("Close"),\n                                  onPressed: () {\n                                    Navigator.of(context).pop();\n                                  },\n                                ),\n                                FlatButton(\n                                  child: Text("Delete"),\n                                  onPressed: () {\n                                    _dbNoteBloc.dispatch(NoteDbEvent(\n                                        value: state[index],\n                                        type: NoteDbEventType.Delete));\n                                    Navigator.of(context).pop();\n                                  },\n                                ),\n                              ],\n                            );\n                          },\n                        ),\n                  ),\n                  Divider(\n                    height: 0,\n                  ),\n                ],\n              );\n            },\n          ),\n        );\n      },\n    );\n  }\n}\n

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正如您所看到的，我在小部件代码中也有显示对话框代码，我很想将其获取，但到目前为止，如果 _dbNoteBloc 不在 Bloc Builder 内部，则显示对话框代码无法访问 _dbNoteBloc。

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感谢您的每一次帮助。

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PS：如果有人需要这里的块代码，它是：

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import \'package:bloc/bloc.dart\';\nimport "note_model.dart";\nimport \'db.dart\';\n\nenum NoteDbEventType { Insert, Delete, Update, GetAll }\n\nclass NoteDbEvent {\n  NoteDbEventType type;\n  Note value;\n  NoteDbEvent({this.type, this.value});\n}\n\nclass DatabaseBloc extends Bloc<NoteDbEvent, List<Note>> {\n  final db = DBProvider();\n\n  @override\n  List<Note> get initialState =>  [];\n\n  @override\n  Stream<List<Note>> mapEventToState(List<Note> currentState, NoteDbEvent event) async* {\n    switch (event.type) {\n      case NoteDbEventType.Delete:\n        db.deleteNote(event.value.id);\n        currentState.removeWhere((item) => item.id == event.value.id);\n        yield List.from(currentState);\n        break;\n      case NoteDbEventType.Insert:\n        int id = await db.newNote(event.value);\n        event.value.id = id;\n        currentState.add(event.value);\n        yield List.from(currentState);\n        break;\n      case NoteDbEventType.Update:\n        yield currentState;\n        break;\n      case NoteDbEventType.GetAll:\n        var list = await db.getAllNotes();\n        yield currentState = list;\n        break;\n    }\n  }\n}\n

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Answer 1

BLoC 模式更适合用于管理单个特定小部件（例如屏幕）的状态。

BLoC 模式不是由单个特定小部件使用，而是用于每个 UI 功能。这意味着您的小部件与您的 BLoC 的链接并不困难。您始终可以选择在 UI 的每个部分使用或不使用它。显然，将 BLoC 拆分为多个 BLoC 是您的工作。

对于那些不了解这一点的人：如果您想让 BLoC 模式让您的生活更轻松，您可以使用此处的flutter_bloc包，它可以让您访问许多帮助程序。

如果您需要包裹方面的帮助，也可以联系gitter。

关于显示对话框，您可以使用BlocListener相当新的对话框。