未处理的异常：查找已停用小部件的祖先是不安全的。怎么解决这个问题？

我正在尝试将条纹支付集成到 flutter 移动应用程序中。付款完成后，我希望应用程序执行Navigator.pop(context)。但是，我收到错误消息：

未处理的异常：查找已停用小部件的祖先是不安全的。 E/flutter (2773)：此时 widget 元素树的状态不再稳定。

这是我的条纹支付代码

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

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

class ExistingCardsPageState extends State<ExistingCardsPage> {
 List cards = [];
 StripeService _service = StripeService();

 Future<StripeTransactionResponse> payViaExistingCard(
     BuildContext context, card, amount) 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: '${amount}00', currency: 'USD', card: stripeCard);
    await EasyLoading.dismiss();
    ScaffoldMessenger.of(context).showSnackBar(
       SnackBar(
         content: Text(response.message),
         duration: new Duration(milliseconds: response.success == true ? 1200 : 3000),
       )
   ).closed.then((_) {
     Navigator.pop(context); /////THIS IS THE ERROR/////

   });

   return response;
}

 @override
 Widget build(BuildContext context) {
   final orderProvider = Provider.of<OrderProvider>(context);
    return Scaffold(
     appBar: AppBar(
    iconTheme: IconThemeData(color: Colors.white),
    title: Text('Choose existing card', style: TextStyle(color: Colors.white),),
  ),
  body: FutureBuilder<QuerySnapshot>(
    future: _service.cards.get(),
    builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
      if (snapshot.hasError) {
        return Text('Something went wrong');
      }

      if (snapshot.connectionState == ConnectionState.waiting) {
        return Center(child: CircularProgressIndicator());
      }

      if(snapshot.data.size==0){
        return Center(
          child: Text('No Credit Card in your account'));
      }

      return Container(
        padding: EdgeInsets.only(left: 8, top: 10, right: 8, bottom: 10),
        child: ListView.builder(
          itemCount: snapshot.data.docs.length,
          itemBuilder: (BuildContext context, int index) {
            var card = snapshot.data.docs[index];
            return InkWell(
              onTap: () {
                payViaExistingCard(context, card, orderProvider.amount).then((response) {
                  if(response.success==true){
                    orderProvider.paymentStatus(response.success);
                  }
                });
              },
              child: CreditCardWidget(
                cardNumber: card['cardNumber'],
                expiryDate: card['expiryDate'],
                cardHolderName: card['cardHolderName'],
                cvvCode: card['cvvCode'],
                showBackView: false,
                onCreditCardWidgetChange: (brand) {
                  print(brand);
                },
              ),
            );
          },
        ),
      );
    },
  )
);
}
}

有谁知道代码有什么问题吗？

对 SnackBar 使用全局上下文

// declare as global
GlobalKey<ScaffoldMessengerState> scaffoldMessengerKey=GlobalKey<ScaffoldMessengerState>();

只需将其添加到main.dart file in

   @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'App Name',
      scaffoldMessengerKey: scaffoldMessengerKey, // add this
    );
  }

然后我们可以在应用程序中的任何地方使用它，而无需传递每个页面上下文。

scaffoldMessengerKey.currentState.showSnackBar(SnackBar(
        content: Text(
          "Your Message",
        ),
      ));