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How To Solve "The Method 'call' Was Called On Null. Receiver: Null Tried Calling: Call()" Error On Flutter?

- 1 answer

i am trying to integrate stripe payment method in flutter. i am following the tutorial from https://www.youtube.com/watch?v=VOtmM9i25R4.

i got error that says The method 'call' was called on null. Receiver: null Tried calling: call()

this is the code where the error is

import 'package:flutter/material.dart';
import 'package:flutter_credit_card/credit_card_widget.dart';
import 'package:flutter_easyloading/flutter_easyloading.dart';

import 'package:izzilly_customer/API_service/payment_service/stripe- 
payment-service.dart';
import 'package:stripe_payment/stripe_payment.dart';

class ExistingCardsPage extends StatefulWidget {
   static const String id = 'existing-card';
   ExistingCardsPage({Key key}) : super(key: key);

   @override
   ExistingCardsPageState createState() => ExistingCardsPageState();
} 

class ExistingCardsPageState extends State<ExistingCardsPage> {
  List cards = [{
    'cardNumber': '4242424242424242',
    'expiryDate': '04/24',
    'cardHolderName': 'Muhammad Ahsan Ayaz',
    'cvvCode': '424',
    'showBackView': false,
 }, {
    'cardNumber': '5555555566554444',
    'expiryDate': '04/23',
    'cardHolderName': 'Tracer',
    'cvvCode': '123',
    'showBackView': false,
 }];

 payViaExistingCard(BuildContext context, card) async {

    await EasyLoading.show(status: 'Please wait....' );
    var expiryArr = card['expiryDate'].split('/');
    CreditCard stripeCard = CreditCard(
    number: card['cardNumber'],
    expMonth: int.parse(expiryArr[0]),
    expYear: int.parse(expiryArr[1]),
  );
   var response = await StripeService.payViaExistingCard(
    amount: '2500',
    currency: 'USD',
    card: stripeCard
  );
   await EasyLoading.dismiss();
   ScaffoldMessenger.of(context).showSnackBar(
     SnackBar(
      content: Text(response.message),
      duration: new Duration(milliseconds: 1200),
    )
  ).closed.then((_) {
    Navigator.pop(context);
  });
}

  @override
Widget build(BuildContext context) {
  return Scaffold(
   appBar: AppBar(
    title: Text('Choose existing card'),
  ),
  body: Container(
    padding: EdgeInsets.all(20),
    child: ListView.builder(
      itemCount: cards.length,
      itemBuilder: (BuildContext context, int index) {
        var card = cards[index];
        
          return InkWell(
            onTap: () {
              payViaExistingCard(context, card);
            },
            child: CreditCardWidget(
              cardNumber: card['cardNumber'],
              expiryDate: card['expiryDate'],
              cardHolderName: card['cardHolderName'],
              cvvCode: card['cvvCode'],
              showBackView: false,
            )
          );
        }
       
      },
    ),
  ),
);
 }
} 

and this is the error

error picture

this is the code for CreditCardWidget

const Map<CardType, String> CardTypeIconAsset = <CardType, String>{
CardType.visa: 'icons/visa.png',
CardType.americanExpress: 'icons/amex.png',
CardType.mastercard: 'icons/mastercard.png',
CardType.discover: 'icons/discover.png',
};

 class CreditCardWidget extends StatefulWidget {
   const CreditCardWidget(
  {Key? key,
  required this.cardNumber,
  required this.expiryDate,
  required this.cardHolderName,
  required this.cvvCode,
  required this.showBackView,
  this.animationDuration = const Duration(milliseconds: 500),
  this.height,
  this.width,
  this.textStyle,
  this.cardBgColor = const Color(0xff1b447b),
  this.obscureCardNumber = true,
  this.obscureCardCvv = true,
  this.labelCardHolder = 'CARD HOLDER',
  this.labelExpiredDate = 'MM/YY',
  this.cardType,
  this.isHolderNameVisible = false,
  this.backgroundImage,
  this.glassmorphismConfig,
  this.isChipVisible = true,
  this.isSwipeGestureEnabled = true,
  this.customCardTypeIcons = const <CustomCardTypeIcon>[],
  required this.onCreditCardWidgetChange})
  : super(key: key);

 final String cardNumber;
 final String expiryDate;
 final String cardHolderName;
 final String cvvCode;
 final TextStyle? textStyle;
 final Color cardBgColor;
 final bool showBackView;
 final Duration animationDuration;
 final double? height;
 final double? width;
 final bool obscureCardNumber;
 final bool obscureCardCvv;
 final void Function(CreditCardBrand) onCreditCardWidgetChange;
 final bool isHolderNameVisible;
 final String? backgroundImage;
 final bool isChipVisible;
 final Glassmorphism? glassmorphismConfig;
 final bool isSwipeGestureEnabled;

 final String labelCardHolder;
 final String labelExpiredDate;

 final CardType? cardType;
 final List<CustomCardTypeIcon> customCardTypeIcons;

 @override
  _CreditCardWidgetState createState() => _CreditCardWidgetState();
 }

 class _CreditCardWidgetState extends State<CreditCardWidget>
 with SingleTickerProviderStateMixin {
 late AnimationController controller;
 late Animation<double> _frontRotation;
 late Animation<double> _backRotation;
 late Gradient backgroundGradientColor;
 late bool isFrontVisible = true;
 late bool isGestureUpdate = false;

  bool isAmex = false;

@override
void initState() {
super.initState();

///initialize the animation controller
controller = AnimationController(
  duration: widget.animationDuration,
  vsync: this,
);

_gradientSetup();
_updateRotations(false);
}

void _gradientSetup() {
backgroundGradientColor = LinearGradient(
  // Where the linear gradient begins and ends
  begin: Alignment.topRight,
  end: Alignment.bottomLeft,
  // Add one stop for each color. Stops should increase from 0 to 1
  stops: const <double>[0.1, 0.4, 0.7, 0.9],
  colors: <Color>[
    widget.cardBgColor.withOpacity(1),
    widget.cardBgColor.withOpacity(0.97),
    widget.cardBgColor.withOpacity(0.90),
    widget.cardBgColor.withOpacity(0.86),
  ],
);
}

@override
void dispose() {
 controller.dispose();
 super.dispose();
}

@override
Widget build(BuildContext context) {
///
/// If uer adds CVV then toggle the card from front to back..
/// controller forward starts animation and shows back layout.
/// controller reverse starts animation and shows front layout.
///
if (!isGestureUpdate) {
  _updateRotations(false);
  if (widget.showBackView) {
    controller.forward();
  } else {
    controller.reverse();
  }
} else {
  isGestureUpdate = false;
}

final CardType? cardType = widget.cardType != null
    ? widget.cardType
    : detectCCType(widget.cardNumber);
widget.onCreditCardWidgetChange(CreditCardBrand(cardType));

return Stack(
  children: <Widget>[
    _cardGesture(
      child: AnimationCard(
        animation: _frontRotation,
        child: _buildFrontContainer(),
      ),
    ),
    _cardGesture(
      child: AnimationCard(
        animation: _backRotation,
        child: _buildBackContainer(),
      ),
    ),
  ],
);
}

void _leftRotation() {
  _toggleSide(false);
}

void _rightRotation() {
  _toggleSide(true);
 }

void _toggleSide(bool isRightTap) {
  _updateRotations(!isRightTap);
  if (isFrontVisible) {
   controller.forward();
   isFrontVisible = false;
 } else {
  controller.reverse();
  isFrontVisible = true;
 }
  }

 void _updateRotations(bool isRightSwipe) {
   setState(() {
   final bool rotateToLeft =
      (isFrontVisible && !isRightSwipe) || !isFrontVisible && 
  isRightSwipe;

  ///Initialize the Front to back rotation tween sequence.
  _frontRotation = TweenSequence<double>(
    <TweenSequenceItem<double>>[
      TweenSequenceItem<double>(
        tween: Tween<double>(
                begin: 0.0, end: rotateToLeft ? (pi / 2) : (-pi / 2))
            .chain(CurveTween(curve: Curves.linear)),
        weight: 50.0,
      ),
      TweenSequenceItem<double>(
        tween: ConstantTween<double>(rotateToLeft ? (-pi / 2) : (pi / 
 2)),
        weight: 50.0,
      ),
    ],
  ).animate(controller);

   ///Initialize the Back to Front rotation tween sequence.
  _backRotation = TweenSequence<double>(
    <TweenSequenceItem<double>>[
      TweenSequenceItem<double>(
        tween: ConstantTween<double>(rotateToLeft ? (pi / 2) : (-pi / 
   2)),
        weight: 50.0,
      ),
      TweenSequenceItem<double>(
        tween: Tween<double>(
                begin: rotateToLeft ? (-pi / 2) : (pi / 2), end: 0.0)
            .chain(
          CurveTween(curve: Curves.linear),
        ),
        weight: 50.0,
      ),
    ],
  ).animate(controller);
  });
  }

 ///
 /// Builds a front container containing
 /// Card number, Exp. year and Card holder name
 ///
  Widget _buildFrontContainer() {
 final TextStyle defaultTextStyle =
    Theme.of(context).textTheme.headline6!.merge(
          const TextStyle(
            color: Colors.white,
            fontFamily: 'halter',
            fontSize: 16,
            package: 'flutter_credit_card',
          ),
        );

final String number = widget.obscureCardNumber
    ? widget.cardNumber.replaceAll(RegExp(r'(?<=.{4})\d(?=.{4})'), 
  '*')
    : widget.cardNumber;
 return CardBackground(
  backgroundImage: widget.backgroundImage,
  backgroundGradientColor: backgroundGradientColor,
  glassmorphismConfig: widget.glassmorphismConfig,
  height: widget.height,
  width: widget.width,
  child: Column(
    crossAxisAlignment: CrossAxisAlignment.start,
    children: <Widget>[
      Expanded(
        flex: widget.isChipVisible ? 2 : 0,
        child: Row(
          crossAxisAlignment: CrossAxisAlignment.end,
          children: <Widget>[
            if (widget.isChipVisible)
              Padding(
                padding: const EdgeInsets.only(left: 16),
                child: Image.asset(
                  'icons/chip.png',
                  package: 'flutter_credit_card',
                  scale: 1,
                ),
              ),
            const Spacer(),
            Align(
              alignment: Alignment.topRight,
              child: Padding(
                padding: const EdgeInsets.only(left: 16, right: 16, 
   top: 8),
                child: widget.cardType != null
                    ? getCardTypeImage(widget.cardType)
                    : getCardTypeIcon(widget.cardNumber),
              ),
            ),
          ],
        ),
      ),
      const SizedBox(
        height: 10,
      ),
      Expanded(
        child: Padding(
          padding: const EdgeInsets.only(left: 16),
          child: Text(
            widget.cardNumber.isEmpty ? 'XXXX XXXX XXXX XXXX' : 
   number,
            style: widget.textStyle ?? defaultTextStyle,
          ),
        ),
      ),
      Expanded(
        flex: 1,
        child: Padding(
          padding: const EdgeInsets.only(left: 16),
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: <Widget>[
              Text(
                'VALID\nTHRU',
                style: widget.textStyle ??
                    defaultTextStyle.copyWith(fontSize: 7),
                textAlign: TextAlign.center,
              ),
              const SizedBox(width: 5),
              Text(
                widget.expiryDate.isEmpty
                    ? widget.labelExpiredDate
                    : widget.expiryDate,
                style: widget.textStyle ?? defaultTextStyle,
              ),
            ],
          ),
        ),
      ),
      Visibility(
        visible: widget.isHolderNameVisible,
        child: Expanded(
          child: Padding(
            padding: const EdgeInsets.only(left: 16, right: 16, 
    bottom: 16),
            child: Text(
              widget.cardHolderName.isEmpty
                  ? widget.labelCardHolder
                  : widget.cardHolderName,
              maxLines: 1,
              overflow: TextOverflow.ellipsis,
              style: widget.textStyle ?? defaultTextStyle,
            ),
          ),
        ),
      ),
    ],
  ),
);
}

///
/// Builds a back container containing cvv
  ///
 Widget _buildBackContainer() {
final TextStyle defaultTextStyle =
    Theme.of(context).textTheme.headline6!.merge(
          const TextStyle(
            color: Colors.black,
            fontFamily: 'halter',
            fontSize: 16,
            package: 'flutter_credit_card',
          ),
        );

  final String cvv = widget.obscureCardCvv
    ? widget.cvvCode.replaceAll(RegExp(r'\d'), '*')
    : widget.cvvCode;

  return CardBackground(
  backgroundImage: widget.backgroundImage,
  backgroundGradientColor: backgroundGradientColor,
  glassmorphismConfig: widget.glassmorphismConfig,
  height: widget.height,
  width: widget.width,
  child: Column(
    mainAxisAlignment: MainAxisAlignment.spaceAround,
    crossAxisAlignment: CrossAxisAlignment.start,
    children: <Widget>[
      Expanded(
        flex: 2,
        child: Container(
          margin: const EdgeInsets.only(top: 16),
          height: 48,
          color: Colors.black,
        ),
      ),
      Expanded(
        flex: 2,
        child: Container(
          margin: const EdgeInsets.only(top: 16),
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Expanded(
                flex: 9,
                child: Container(
                  height: 48,
                  color: Colors.white70,
                ),
              ),
              Expanded(
                flex: 3,
                child: Container(
                  color: Colors.white,
                  child: Padding(
                    padding: const EdgeInsets.all(5),
                    child: Text(
                      widget.cvvCode.isEmpty
                          ? isAmex
                              ? 'XXXX'
                              : 'XXX'
                          : cvv,
                      maxLines: 1,
                      style: widget.textStyle ?? defaultTextStyle,
                    ),
                  ),
                ),
              )
            ],
          ),
        ),
      ),
      Expanded(
        flex: 2,
        child: Align(
          alignment: Alignment.bottomRight,
          child: Padding(
            padding: const EdgeInsets.only(left: 16, right: 16, 
  bottom: 16),
            child: widget.cardType != null
                ? getCardTypeImage(widget.cardType)
                : getCardTypeIcon(widget.cardNumber),
          ),
        ),
      ),
    ],
  ),
);
}

Widget _cardGesture({required Widget child}) {
bool isRightSwipe = true;
return widget.isSwipeGestureEnabled
    ? GestureDetector(
        onPanEnd: (_) {
          isGestureUpdate = true;
          if (isRightSwipe) {
            _leftRotation();
          } else {
            _rightRotation();
          }
        },
        onPanUpdate: (DragUpdateDetails details) {
          // Swiping in right direction.
          if (details.delta.dx > 0) {
            isRightSwipe = true;
          }

          // Swiping in left direction.
          if (details.delta.dx < 0) {
            isRightSwipe = false;
          }
        },
        child: child,
      )
    : child;
}

/// Credit Card prefix patterns as of March 2019
/// A [List<String>] represents a range.
/// i.e. ['51', '55'] represents the range of cards starting with 
'51' 
 to those starting with '55'
 Map<CardType, Set<List<String>>> cardNumPatterns =
  <CardType, Set<List<String>>>{
CardType.visa: <List<String>>{
  <String>['4'],
},
CardType.americanExpress: <List<String>>{
  <String>['34'],
  <String>['37'],
},
CardType.discover: <List<String>>{
  <String>['6011'],
  <String>['622126', '622925'],
  <String>['644', '649'],
  <String>['65']
},
CardType.mastercard: <List<String>>{
  <String>['51', '55'],
  <String>['2221', '2229'],
  <String>['223', '229'],
  <String>['23', '26'],
  <String>['270', '271'],
  <String>['2720'],
},
   };

 /// This function determines the Credit Card type based on the 
  cardPatterns
 /// and returns it.
 CardType detectCCType(String cardNumber) {
//Default card type is other
CardType cardType = CardType.otherBrand;

if (cardNumber.isEmpty) {
  return cardType;
}

  cardNumPatterns.forEach(
  (CardType type, Set<List<String>> patterns) {
    for (List<String> patternRange in patterns) {
      // Remove any spaces
      String ccPatternStr =
          cardNumber.replaceAll(RegExp(r'\s+\b|\b\s'), '');
      final int rangeLen = patternRange[0].length;
      // Trim the Credit Card number string to match the pattern 
     prefix length
      if (rangeLen < cardNumber.length) {
        ccPatternStr = ccPatternStr.substring(0, rangeLen);
      }

      if (patternRange.length > 1) {
        // Convert the prefix range into numbers then make sure the
        // Credit Card num is in the pattern range.
        // Because Strings don't have '>=' type operators
        final int ccPrefixAsInt = int.parse(ccPatternStr);
        final int startPatternPrefixAsInt = int.parse(patternRange[0]);
        final int endPatternPrefixAsInt = int.parse(patternRange[1]);
        if (ccPrefixAsInt >= startPatternPrefixAsInt &&
            ccPrefixAsInt <= endPatternPrefixAsInt) {
          // Found a match
          cardType = type;
          break;
        }
      } else {
        // Just compare the single pattern prefix with the Credit 
  Card prefix
        if (ccPatternStr == patternRange[0]) {
          // Found a match
          cardType = type;
          break;
        }
      }
    }
  },
);

return cardType;
 }

Widget getCardTypeImage(CardType? cardType) {
final List<CustomCardTypeIcon> customCardTypeIcon = 
getCustomCardTypeIcon(cardType!);
if(customCardTypeIcon.isNotEmpty){
  return customCardTypeIcon.first.cardImage;
} else {
  return Image.asset(
    CardTypeIconAsset[cardType]!,
    height: 48,
    width: 48,
    package: 'flutter_credit_card',
  );
}
}

// This method returns the icon for the visa card type if found
// else will return the empty container
Widget getCardTypeIcon(String cardNumber) {
Widget icon;
final CardType ccType = detectCCType(cardNumber);
final List<CustomCardTypeIcon> customCardTypeIcon = 
 getCustomCardTypeIcon(ccType);
if (customCardTypeIcon.isNotEmpty) {
  icon = customCardTypeIcon.first.cardImage;
  isAmex = ccType == CardType.americanExpress;
 } else {
  switch (ccType) {
    case CardType.visa:
      icon = Image.asset(
        CardTypeIconAsset[ccType]!,
        height: 48,
        width: 48,
        package: 'flutter_credit_card',
      );
      isAmex = false;
      break;

    case CardType.americanExpress:
      icon = Image.asset(
        CardTypeIconAsset[ccType]!,
        height: 48,
        width: 48,
        package: 'flutter_credit_card',
      );
      isAmex = true;
      break;

    case CardType.mastercard:
      icon = Image.asset(
        CardTypeIconAsset[ccType]!,
        height: 48,
        width: 48,
        package: 'flutter_credit_card',
      );
      isAmex = false;
      break;

    case CardType.discover:
      icon = Image.asset(
        CardTypeIconAsset[ccType]!,
        height: 48,
        width: 48,
        package: 'flutter_credit_card',
      );
      isAmex = false;
      break;

    default:
      icon = Container(
        height: 48,
        width: 48,
      );
      isAmex = false;
      break;
  }
}

return icon;
}

List<CustomCardTypeIcon> getCustomCardTypeIcon(CardType 
 currentCardType) =>
  widget.customCardTypeIcons
      .where((CustomCardTypeIcon element) =>
          element.cardType == currentCardType)
      .toList();
 }

 class MaskedTextController extends TextEditingController {
 MaskedTextController(
  {String? text, required this.mask, Map<String, RegExp>? 
 translator})
  : super(text: text) {
this.translator = translator ?? 
 MaskedTextController.getDefaultTranslator();

addListener(() {
  final String previous = _lastUpdatedText;
  if (beforeChange(previous, this.text)) {
    updateText(this.text);
    afterChange(previous, this.text);
  } else {
    updateText(_lastUpdatedText);
  }
});

updateText(this.text);
}

 String mask;

late Map<String, RegExp> translator;

Function afterChange = (String previous, String next) {};
Function beforeChange = (String previous, String next) {
return true;
};

String _lastUpdatedText = '';

void updateText(String text) {
if (text.isNotEmpty) {
  this.text = _applyMask(mask, text);
} else {
  this.text = '';
}

_lastUpdatedText = this.text;
}

void updateMask(String mask, {bool moveCursorToEnd = true}) {
this.mask = mask;
updateText(text);

if (moveCursorToEnd) {
  this.moveCursorToEnd();
}
}

void moveCursorToEnd() {
final String text = _lastUpdatedText;
selection = TextSelection.fromPosition(TextPosition(offset: 
text.length));
}

@override
set text(String newText) {
 if (super.text != newText) {
  super.text = newText;
  moveCursorToEnd();
}
}

static Map<String, RegExp> getDefaultTranslator() {
return <String, RegExp>{
  'A': RegExp(r'[A-Za-z]'),
  '0': RegExp(r'[0-9]'),
  '@': RegExp(r'[A-Za-z0-9]'),
  '*': RegExp(r'.*')
};
}

String _applyMask(String? mask, String value) {
String result = '';

int maskCharIndex = 0;
int valueCharIndex = 0;

 while (true) {
  // if mask is ended, break.
  if (maskCharIndex == mask!.length) {
    break;
  }

  // if value is ended, break.
  if (valueCharIndex == value.length) {
    break;
  }

  final String maskChar = mask[maskCharIndex];
  final String valueChar = value[valueCharIndex];

  // value equals mask, just set
  if (maskChar == valueChar) {
    result += maskChar;
    valueCharIndex += 1;
    maskCharIndex += 1;
    continue;
  }

  // apply translator if match
  if (translator.containsKey(maskChar)) {
    if (translator[maskChar]!.hasMatch(valueChar)) {
      result += valueChar;
      maskCharIndex += 1;
    }

    valueCharIndex += 1;
    continue;
  }

  // not masked value, fixed char on mask
  result += maskChar;
  maskCharIndex += 1;
  continue;
  }

   return result;
 }
}

enum CardType {
   otherBrand,
   mastercard,
  visa,
  americanExpress,
  discover,
}

can someone help me to fix this??

thank you very much

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Answer

The issue is CreditCardWidget has a required parameter onCreditCardWidgetChange which expects a function, it's missing in your code. You should change your code to pass that:

CreditCardWidget(
   cardNumber: card['cardNumber'],
   expiryDate: card['expiryDate'],
   cardHolderName: card['cardHolderName'],
   cvvCode: card['cvvCode'],
   showBackView: false,
   onCreditCardWidgetChange: (brand) {
      print(brand);
   },
),
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source: stackoverflow.com
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