NICE pay 연동 - 01

 @override
  Widget build(BuildContext context) {
    var shoppingController = Get.put(GetShoppingsController());

    return Scaffold(
        appBar: LeadingAppBar(
          appBar: AppBar(),
          title: 'NICE 결제',
        ),
        body: SafeArea(
          child: InAppWebView(
            initialUrlRequest: URLRequest(
              url: Uri.parse(
                '위의 개발한 서버의 요청 URL/payment',
              ),
              body: Uint8List.fromList(
                utf8.encode(
                  getRequestBody(shoppingController),  // 요청 데이터
                ),
              ),
              method: 'POST',
              headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
              },
            ),
            initialOptions: options,
            onWebViewCreated: (controller) {
              controller.addJavaScriptHandler(
                  handlerName: 'NicepayHandler',
                  callback: (arguments) {
                    Map<String, dynamic> resp = jsonDecode(arguments[0]);
                    if (resp['paySuccess'] == 'true') {
                      Map<String, dynamic> param = {};
                      param['reportSeq'] = shoppingController.reportSeq.value;
                      param['addrSeq'] = shoppingController.addrSeq.value;
                      param['impUid'] = resp['tid'];
                      List<dynamic> prdAmountList = [];
                      for (var i = 0;
                          i < shoppingController.prdList.length;
                          i++) {
                        var prd = shoppingController.prdList[i];
                        prdAmountList.add({
                          'prdKey': prd['prdKey'],
                          'payAmount': prd['amount']
                        });
                      }
                      param['prdAmountList'] = prdAmountList;

                      postBuysApi(param, context);
                    } else {
                      Get.back(result: resp);
                    }
                  });
            },
            shouldOverrideUrlLoading: (controller, navigationAction) async {
              String requestUrl = navigationAction.request.url.toString();
              debugPrint('웹뷰 [onUpdateVisitedHistory]: $requestUrl');

              if (!requestUrl.startsWith('http') &&
                  !requestUrl.startsWith('https')) {
                if (Platform.isAndroid) {
                  getAppUrl(requestUrl);
                  return NavigationActionPolicy.CANCEL;
                } else if (Platform.isIOS) {
                  await launchUrl(
                    Uri.parse(requestUrl),
                  );
                  return NavigationActionPolicy.CANCEL;
                }
              }
              return NavigationActionPolicy.ALLOW;
            },
          ),
        ));
  }

...
  /// 결제 요청 파라미터
  String getRequestBody(GetShoppingsController controller) {
    String result = "";
    result += "goodsName=${controller.prdName.value}";      // 상품명
    result += "&price=${controller.payAmount.value}";       // 결제금액
    result += "&buyerName=${controller.buyerName.value}";   // 결제자 이름
    result += "&buyerTel=${controller.buyerTel.value}";     // 결제자 전화번호
    return result;
  }

  /// 앱 실행 및 설치 MethodChannel 호출
  Future getAppUrl(String url) async {
    await platform.invokeMethod('getAppUrl', <String, Object>{'url': url}).then(
        (value) async {
      debugPrint('paring url : $value');

      if (await canLaunchUrl(Uri.parse(value))) {
        await launchUrl(
          Uri.parse(value),
        );
        return;
      } else {
        debugPrint('이동 불가능한 URL입니다.');
        return;
      }
    });
  }