What is the equivalent of Xamarin MessagingCenter in Flutter? - xamarin

Question

With Xamarin, We usually use Message-Center to send a message to any page when Application is running (start App or app is background).
With Flutter, have we any ways that send a message same with Message-Center of Xamarin.Forms?

Answer 1

Based on my research, you can use Channel to achieve that.
BasicMessageChannel is a similar channel.
Native part.
private final Activity activity;
private final BasicMessageChannel<String> messageChannel;
static BasicMessageChannelPlugin registerWith(FlutterView flutterView) {
return new BasicMessageChannelPlugin(flutterView);
}
private BasicMessageChannelPlugin(FlutterView flutterView) {
this.activity = (Activity) flutterView.getContext();
this.messageChannel = new BasicMessageChannel<>(flutterView, "BasicMessageChannelPlugin", StringCodec.INSTANCE);
//Set up a message handler to handle messages from Dart
messageChannel.setMessageHandler(this);
}
#Override
public void onMessage(String s, BasicMessageChannel.Reply<String> reply) {//Handle messages from Dart
reply.reply("BasicMessageChannel：" + s);//Can reply by `reply`
if (activity instanceof IShowMessage) {
((IShowMessage) activity).onShowMessage(s);
}
Toast.makeText(activity, s, Toast.LENGTH_SHORT).show();
}
/**
* Send Dart a message and receive feedback from Dart
*
* #param message Content of the message to send to Dart
* #param callback Feedback from Dart
*/
void send(String message, BasicMessageChannel.Reply<String> callback) {
messageChannel.send(message, callback);
}
#Override
public void reply(String s) {
}
}
Dart Part
import 'package:flutter/services.dart';
static const BasicMessageChannel _basicMessageChannel =
const BasicMessageChannel('BasicMessageChannelPlugin', StringCodec());
//Use BasicMessageChannel to receive messages from Native and reply to Native
_basicMessageChannel
.setMessageHandler((String message) => Future<String>(() {
setState(() {
showMessage = message;
});
return "receive Native's message：" + message;
}));
//use BasicMessageChannelsend message to Native And accept Native's reply
String response;
try {
response = await _basicMessageChannel.send(value);
} on PlatformException catch (e) {
print(e);
}
Here is blog about it.
https://stablekernel.com/flutter-platform-channels-quick-start/

Answer 2

I've been searching the same implementation in Flutter. So far I haven't found any.
This is my simple implementation
import 'package:meta/meta.dart';
abstract class MessagingService {
void subscribe(Object subscriber, {#required String channel, #required void Function(Object) action});
void unsubscribe(Object subscriber, {#required String channel});
void send({#required String channel, Object parameter});
}
class MessagingServiceImpl implements MessagingService {
static final _map = <String, Map<String, void Function(Object)>>{};
#override
void subscribe(Object subscriber, {#required String channel, #required void Function(Object) action}) {
assert(subscriber != null);
assert(channel != null);
assert(channel.isNotEmpty);
assert(action != null);
if (!_map.containsKey(channel)) {
_map[channel] = {};
}
_map[channel].putIfAbsent(subscriber.hashCode.toString(), () => action);
}
#override
void send({#required String channel, Object parameter}) {
assert(channel != null);
assert(channel.isNotEmpty);
if (_map.containsKey(channel)) {
for (final action in _map[channel].values) {
action(parameter);
}
}
}
#override
void unsubscribe(Object subscriber, {#required String channel}) {
if (_map.containsKey(channel)) {
_map[channel].removeWhere((k, v) => k == subscriber.hashCode.toString());
}
}
}