postMessage method not working

[andreibosco]

I'm trying to use postMessage to call a method on Unity and I'm getting the following error:

/MethodChannel#unity_view_0( 6284): Failed to handle method call
E/MethodChannel#unity_view_0( 6284): java.lang.ClassCastException
E/MethodChannel#unity_view_0( 6284): 	at io.flutter.plugin.common.MethodCall.argument(MethodCall.java:74)
E/MethodChannel#unity_view_0( 6284): 	at com.rexraphael.flutterunitywidget.FlutterUnityView.onMethodCall(FlutterUnityView.java:54)
E/MethodChannel#unity_view_0( 6284): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:201)
E/MethodChannel#unity_view_0( 6284): 	at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:88)
E/MethodChannel#unity_view_0( 6284): 	at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:219)
E/MethodChannel#unity_view_0( 6284): 	at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#unity_view_0( 6284): 	at android.os.MessageQueue.next(MessageQueue.java:325)
E/MethodChannel#unity_view_0( 6284): 	at android.os.Looper.loop(Looper.java:142)
E/MethodChannel#unity_view_0( 6284): 	at android.app.ActivityThread.main(ActivityThread.java:6494)
E/MethodChannel#unity_view_0( 6284): 	at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#unity_view_0( 6284): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
E/MethodChannel#unity_view_0( 6284): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
E/flutter ( 6284): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: PlatformException(error, null, null)
E/flutter ( 6284): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:564:7)
E/flutter ( 6284): #1      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:302:33)
E/flutter ( 6284): <asynchronous suspension>
E/flutter ( 6284): #2      UnityWidgetController.postMessage (package:flutter_unity_widget/flutter_unity_widget.dart:44:14)
E/flutter ( 6284): #3      _UnityTestScreenState.build.<anonymous closure> (package:hydrocephaly_app/unity_test.dart:43:48)
E/flutter ( 6284): #4      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:511:14)
E/flutter ( 6284): #5      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:566:30)
E/flutter ( 6284): #6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:166:24)
E/flutter ( 6284): #7      TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:240:9)
E/flutter ( 6284): #8      TapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:177:9)
E/flutter ( 6284): #9      PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:436:9)
E/flutter ( 6284): #10     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:73:12)
E/flutter ( 6284): #11     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:11)
E/flutter ( 6284): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:221:19)
E/flutter ( 6284): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:199:22)
E/flutter ( 6284): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
E/flutter ( 6284): #15     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
E/flutter ( 6284): #16     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
E/flutter ( 6284): #17     _rootRunUnary (dart:async/zone.dart:1136:13)
E/flutter ( 6284): #18     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 6284): #19     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 6284): #20     _invoke1 (dart:ui/hooks.dart:233:10)
E/flutter ( 6284): #21     _dispatchPointerDataPacket (dart:ui/hooks.dart:154:5)
E/flutter ( 6284): 

This is how I'm calling it on flutter:

_unityWidgetController.postMessage("Cube", "ChangeObjMaterial", "_");

[juicycleff]

Did you see the demo example usage?

[thomas-stockx]

The demo example didn't use postMessage (which wasn't working). I've opened a pull request with the fix.