How can i listen if the "platform.invokeMethod" is finished?

So, i'm trying to integrating flutter with java third party plugin. So, i do this

try {
     await platform
          .invokeMethod('androidNativePayment', {"data": parameter.toString()});

    } on PlatformException catch (e) {
     print("something went wrong");

In the third party plugin it will open an activity. Is it possible to listen if the activity is closed ?

Note : I can't access the the startActivity();