更新事件后流值不变.(Flutter，整体)

Question

我对扑动真的很陌生，现在我正在研究扑动中的整体模式。所以我试图实现一个用户点击按钮(蓝色或绿色(的功能，它应该将主题颜色更改为蓝色或绿色。但问题是，我将initiaData设置为紫色，即使用户单击绿色或蓝色按钮，它也只显示橙色主题。

event.dart

abstract class ChangeColorEvent {}
class ChangeToGreen extends ChangeColorEvent {}
class ChangeToBlue extends ChangeColorEvent {}

bloc.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:theme_change/bloc/colorTheme/event.dart';
class ColorThemeBloc {
var _theme =
ThemeData(brightness: Brightness.light, primaryColor: Colors.orange);
final _colorStateController = StreamController();
StreamSink get _inTheme => _colorStateController.sink;
Stream get theme => _colorStateController.stream;
final _colorEventController = StreamController<ChangeColorEvent>();

Sink<ChangeColorEvent> get changeColorEventSink => _colorEventController.sink;
ColorThemeBloc() {
//wherever there's a new event we want to map it to a new state
_colorEventController.stream.listen(_mapEventToState);
}
void _mapEventToState(ChangeColorEvent event) {
print(event);
if (event is ChangeToGreen)
_theme =
ThemeData(brightness: Brightness.light, primaryColor: Colors.red);
else
_theme =
ThemeData(brightness: Brightness.light, primaryColor: Colors.pink);
_inTheme.add(_theme);
print(_theme);
}
void dispose() {
_colorEventController.close();
_colorStateController.close();
}
}

themeChange.dart

import 'package:flutter/material.dart';
import 'package:theme_change/bloc/colorTheme/bloc.dart';
import 'package:theme_change/bloc/colorTheme/event.dart';
class ThemeChange extends StatelessWidget {
// final bool isDarkThemeEnabled;
// final ThemeBloc bloc;
final _bloc = ColorThemeBloc();
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
RaisedButton(
onPressed: () {
Navigator.pop(context);
},
color: Colors.grey,
child: Text('GO BACK'),
),
// ListTile(
//   title: Text("Dark Theme"),
//   trailing: Switch(
//       value: isDarkThemeEnabled, onChanged: bloc.changeTheTheme),
// ),
RaisedButton(
onPressed: () => _bloc.changeColorEventSink.add(ChangeToBlue()),
color: Colors.blue,
child: Text('blue'),
),
RaisedButton(
onPressed: () => _bloc.changeColorEventSink.add(ChangeToGreen()),
color: Colors.green,
child: Text('Green'),
)
],
),
),
);
}
}

main.dart

class MyApp extends StatelessWidget {
final _bloc = ColorThemeBloc();
@override
Widget build(BuildContext context) {
return StreamBuilder(
initialData: ThemeData(
brightness: Brightness.light, primaryColor: Colors.purple),
stream: _bloc.theme,
builder: (context, snapshot) {
return MaterialApp(
theme: snapshot.data,
title: 'Flutter Demo',
home: DemoScreen(),
);
});
}
}

Answer 1

您还没有在抽象事件上扩展Equatable，它用于识别事件对象是否相同。将您的事件类别更改为以下类别：

abstract class ChangeColorEvent extends Equatable{}
class ChangeToGreen extends ChangeColorEvent {
// Add props, if you want to return data, else 
}
class ChangeToBlue extends ChangeColorEvent {
// Add props, if you want to return data, else 
}