Unhandled Exception: Instance of 'StripeConfigException' - flutter

Question

I want to intigrate stripe payment but i get this error
I am using flutter_stripe: ^8.0.0+1
ERROR MESSAGES
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Instance of 'StripeConfigException'
E/flutter (20428): #0 Stripe.publishableKey (package:flutter_stripe/src/stripe.dart:30:7)
E/flutter (20428): #1 Stripe.applySettings (package:flutter_stripe/src/stripe.dart:104:25)
E/flutter (20428): #2 Stripe._awaitForSettings (package:flutter_stripe/src/stripe.dart:624:25)
E/flutter (20428): #3 Stripe.initPaymentSheet (package:flutter_stripe/src/stripe.dart:463:11)
E/flutter (20428): #4 _stripeState.intpayment (package:ecommerce/payment_intigration/stripe.dart:42:23)
E/flutter (20428):
E/flutter (20428):
I/flutter (20428): Instance of 'StripeConfigException'
CODE
void main() {
WidgetsFlutterBinding.ensureInitialized();
Stripe.publishableKey = 'key';
runApp( MaterialApp(
home: MediaQuery(
data: MediaQueryData(),
child: stripe(),
),
),);
}
class stripe extends StatefulWidget {
const stripe({Key? key}) : super(key: key);
#override
State<stripe> createState() => _stripeState();
}
class _stripeState extends State<stripe> {
Future<void> intpayment(
{required String email, required double amount})async{
try{
final response= await http.post(Uri.parse("https://api.stripe.com/v1/payment_intents")
,body:{
"receipt_email": email,
"amount": amount.toInt().toString(),
"currency": "usd"
},
headers: {
'Authorization': 'Bearer ' + 'secret key',
'Content-Type': 'application/x-www-form-urlencoded'
}
);
final jsonresponse=jsonDecode(response.body);
print(jsonresponse.toString());
Stripe.instance.initPaymentSheet(paymentSheetParameters: SetupPaymentSheetParameters(
paymentIntentClientSecret: jsonresponse['paymentIntent'],
merchantDisplayName: 'Grocery Flutter course',
customerId: jsonresponse['customer'],
customerEphemeralKeySecret: jsonresponse['ephemeralKey'],
));
await Stripe.instance.presentPaymentSheet();
print("payment successfull");
}
catch(e){
if (e is StripeException) {
print(e);
}
print(e);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Payment Demo'),
),
body: Center(
child: ElevatedButton(
onPressed: () {
intpayment(email: "zohaib6778#gmail.com", amount: 50.0);
},
child: Text("Pay20\$"),
),
),
);
}
}
`