How to fix stripe payment in flutter

Question

i have the issue on flutter_stripe_payment i am getting this error MissingPluginException (MissingPluginException(No implementation found for method setPublishableKey on channel stripe_payment))

1. i have trid on MainActivity extend from FlutterActivity to FlutterFragmentActivity.
2. i changing from minSdkVersion 16 to minSdkVersion 21 inside build.gradle in android > app
3. i added ext.kotlin_version = '1.2.71' inside build.gradle in Android folder

    import 'package:app/UiHelper/AppBarHelper.dart';
    import 'package:app/UiHelper/ColorHelper.dart';
    import 'package:flutter/cupertino.dart';
    import 'package:flutter/material.dart';
    import 'package:stripe_payment/stripe_payment.dart';

    class MenuBookingScreen extends StatelessWidget {
       @override
       Widget build(BuildContext context) {
        return DrawWidget();
      }
    }

    class _ViewState extends State<DrawWidget> {
      @override
      void initState() {
        super.initState();
        initAction();
        // this part throw error while hot reload
        StripeSource.setPublishableKey("mykey");
      }

      initAction() async {}

      @override
      Widget build(BuildContext context) {
        return Scaffold(
            appBar: AppBarHelper().appBarGenerator(context),
            backgroundColor: ColorHelper().appBackground,
            body: Material(
                color: ColorHelper().appBody, child: uIDomElement(context)));
      }

      Widget uIDomElement(BuildContext context) {
        var _size = MediaQuery.of(context).size;
        return Container(
          width: _size.width,
          child: RaisedButton(
            color: Colors.indigo,
            textColor: Colors.white,
            disabledColor: Colors.grey,
            disabledTextColor: Colors.black,
            padding: EdgeInsets.all(13),
            splashColor: Colors.blueAccent,
            shape: RoundedRectangleBorder(borderRadius:BorderRadius.circular(5.0)),
            onPressed: () {
              // Add Card
            },
            child: Row(
              children: <Widget>[
                Icon(Icons.credit_card),
                SizedBox(
                  width: 15,
                ),
                Text("Add Card")
              ],
            ),
          ),
        );
      }
    }

    class DrawWidget extends StatefulWidget {
      @override
      _ViewState createState() => _ViewState();
    }

Answer 1

Probably too late, but in case someone else bumps into this problem. 'flutter clean' did the trick for me..