stream value does not changed after update event.. (Flutter,bloc) - flutter

Question

I'm really new to flutter and now I'm studying bloc pattern in flutter.
so I'm trying to implement a function which user click button (blue or green), it should change the theme color blue or green.
but the problem is I set initiaData as purple color and it just shows orange theme even user click the green or blue button.
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

You haven't extended Equatable on Abstract Event, which is used to identify if event Object is same or not. change your event class to following :
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
}