Channel Invokemethod from native android not invoking the flutter method - flutter

Question

Basically I'm invoking a payment sdk in native android(kotlin) using platform channel. SDK is initialised successfully. After payment transaction I will receive the payment status in a kotlin file which actually extends sdk class files (not an activity). From this callback method I need to pass the status to the flutter dart code. Everything runs successfully without any error but while passing the payment status flutter method is not invoked.
Flutter dart code.
#override
void initState() {
// TODO: implement initState
super.initState();
platform.setMethodCallHandler(_handlePaymentResponse); // To call from native android after payment response.
}
// Invoked from Native Android after payment response.
Future<dynamic> _handlePaymentResponse(MethodCall call) async {
print('_handlePaymentResponse method called');
switch(call.method) {
case "message":
debugPrint('From Native====' + call.arguments);
return new Future.value("");
}
}
// On button click this method will be invoked.
Future<void> _initializeSDK() async {
print('Token $token');
try {
await platform.invokeMethod('callPaymentSDK');
} on PlatformException catch (e) {
print("Failed to initialize SDK : '${e.message}'.");
}
}
Native Android : Paymentstatus.kt
class PaymentResponse() : LibraryPaymentStatusProtocol, Parcelable {
//val channel = MethodChannel(flutterView, MainActivity.CHANNEL)
var backgroundFlutterView: FlutterNativeView? = null
override fun paymentStatus(p0: String?, p1: Activity?) {
if (p1 != null) {
Handler(Looper.getMainLooper()).post {
Log.v("PaymentResponse", "Main thread called")
backgroundFlutterView = FlutterNativeView(p1, true)
val channel = MethodChannel(backgroundFlutterView, MainActivity.CHANNEL)
channel.invokeMethod("message", p0); // Invoking Flutter method
}
}
}
}

Answer 1

I ran in to the same issue, and in the end the solution that worked for me (not sure if this is the ideal approach) was to store a reference to the FlutterEngine inside my MainActivity like so:
class MainActivity: FlutterActivity() {
companion object {
var flutterEngineInstance: FlutterEngine? = null
}
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
flutterEngineInstance = flutterEngine
}
}
In my code I would then just invoke a method like this:
MethodChannel(
MainActivity.flutterEngineInstance.dartExecutor.binaryMessenger,
"com.example"
).invokeMethod("method", mapOf())

Answer 2

For my case i didn't receive data from android native to flutter when i called channel.invokeMethod from OnCreate() in MainActivity: FlutterActivity()
so i added channel.invokeMethod( ... ) inside onStart() method, its worked.
also you can use:
runOnUiThread { channel.invokeMethod( ... ) }
or
Handler(Looper.getMainLooper()).post { channel.invokeMethod( ... ) }