Error in flutter : <asynchronous suspension> - flutter

Question

I want to show a dialog box after product add successfully but when I clicking on Add To Cart Button then I am getting that type of error which is in image.
This dialog box want to show using httpException, in product_detailpage.dart page where i use this httpExcetion there are i use dotted line.
This is my cart_api.dart page
import 'dart:convert';
import 'package:hospital/CartPage/Cart_Api/cart_http_exception.dart';
import 'package:hospital/customApiVariable.dart';
import 'package:http/http.dart' as http;
Future add_to_cart_fn(
String quantity, String plistId, String uid, String sid) async {
var url = Uri.parse(
'$ecommerceBaseUrl/addToCartApi.php?a2rTokenKey=$a2rTokenKey&action=addToCart&uid=60daaedd3b9f8751161');
print('add_to_cart_url:' + url.toString());
final response = await http.post(url, headers: {
"Accept": "Application/json"
}, body: {
"quantity": quantity,
"plistId": plistId,
"uid": uid,
"sid": sid,
});
print("ae" + response.body);
final convertderDatatoJson = jsonDecode(response.body);
try {
if (convertderDatatoJson['status'] == "true") {
print('status' + convertderDatatoJson['status']);
print('msg' + convertderDatatoJson['msg']);
throw HttpException(convertderDatatoJson['msg']);
}
} catch (e) {
throw e;
}
return convertderDatatoJson;
}
this is my httpException.dart page
class HttpException implements Exception {
final msg;
HttpException(this.msg);
#override
String toString() {
// TODO: implement toString
return msg;
}
}
This is my product_detailPage.dart page,
import 'dart:convert';
import 'package:carousel_pro/carousel_pro.dart';
import 'package:flutter/material.dart';
import 'package:hospital/CartPage/Cart_Api/cart_api.dart';
import 'package:hospital/CartPage/Cart_Api/cart_http_exception.dart';
import 'package:hospital/CartPage/pages/cartPage.dart';
import 'package:hospital/Drawer/dropdown_menu.dart';
import 'package:hospital/ProductDetailsPage/product_detailPage.dart';
import 'package:hospital/ProductDetailsPage/related_product_page.dart';
import 'package:hospital/SecondSection/Medicine/medicine_page.dart';
import 'package:hospital/constant.dart';
import 'package:hospital/customApiVariable.dart';
import 'package:http/http.dart' as http;
import 'package:line_icons/line_icons.dart';
import 'package:provider/provider.dart';
class DetailPage extends StatefulWidget {
final plistId;
const DetailPage({Key key, this.plistId}) : super(key: key);
#override
_DetailPageState createState() => _DetailPageState();
}
class _DetailPageState extends State<DetailPage> {
final GlobalKey<FormState> _formKey = GlobalKey();
int quantity = 1;
var response;
var detailPageApi;
#override
void initState() {
super.initState();
fetchData(widget.plistId);
}
fetchData(var consultWithDoctor) async {
a2rTokenKey=carpet1234');
var api = Uri.parse(
'$ecommerceBaseUrl/productListApi.php?a2rTokenKey=$a2rTokenKey&plistId=${widget.plistId}');
response = await http.get(
api,
);
print("detailPageApi " + api.toString());
print("detailPageBody " + response.body);
// in double quotes drink is key value of json
detailPageApi = jsonDecode(response.body);
print("detailPagelist " + detailPageApi.toString());
// return doctorDetailsApi;
setState(() {});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: kGreen,
title: Text(
"Details",
style: TextStyle(fontStyle: FontStyle.italic),
),
actions: [
IconButton(
icon: Icon(Icons.shopping_cart),
// onPressed: () => print("open cart"),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Cartpage()),
);
},
),
DropDownMenu(),
],
),
body: Container(
child: response != null
? ListView.builder(
// itemCount: categoryApi.length.clamp(0, 3),//THis is for showed minimun length of item listview.builder flutter
itemCount: detailPageApi.length.clamp(0, 1),
scrollDirection: Axis.vertical,
physics: ScrollPhysics(),
shrinkWrap: true,
itemBuilder: (context, index) {
var details = detailPageApi[index];
if (details['num'] == 0) {
return Center(
child: CircularProgressIndicator(
backgroundColor: Colors.white,
),
);
}
return Column(
children: <Widget>[
Hero(
tag: "1",
child: SizedBox(
height: 300.0,
width: 300.0,
child: Carousel(
boxFit: BoxFit.cover,
autoplay: false,
animationCurve: Curves.fastOutSlowIn,
animationDuration: Duration(milliseconds: 800),
dotSize: 6.0,
dotIncreasedColor: Colors.black,
dotBgColor: Colors.transparent,
// dotPosition: DotPosition.topRight,
dotVerticalPadding: 10.0,
showIndicator: true,
indicatorBgPadding: 7.0,
images: [
NetworkImage(details['pImgImg']),
],
),
),
),
SizedBox(
height: 50,
),
Padding(
padding: const EdgeInsets.only(left: 20, right: 20),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
"Name :",
style: TextStyle(
fontSize: 18,
height: 1.5,
fontWeight: FontWeight.w500),
),
SizedBox(
width: 20,
),
Flexible(
child: Text(
// widget.details,
details['productName'],
style: TextStyle(
fontSize: 17,
height: 1.5,
fontWeight: FontWeight.w500),
),
),
],
),
),
SizedBox(
height: 20,
),
Padding(
padding: const EdgeInsets.only(left: 20, right: 20),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
"Details :",
style: TextStyle(
fontSize: 18,
height: 1.5,
fontWeight: FontWeight.w500),
),
SizedBox(
width: 20,
),
Flexible(
child: Text(
// widget.details,
details['productDescription'],
style: TextStyle(
fontSize: 17,
height: 1.5,
fontWeight: FontWeight.w500),
),
),
],
),
),
SizedBox(
height: 20,
),
Padding(
padding: const EdgeInsets.only(left: 20, right: 20),
child: Row(
children: <Widget>[
Text(
"Price :",
style: TextStyle(
fontSize: 18, fontWeight: FontWeight.w500),
),
SizedBox(
width: 20,
),
Row(
children: <Widget>[
Text(
// "Rs " + widget.pPromotionPrice,
"Rs 55.0",
style: TextStyle(
fontSize: 17,
fontWeight: FontWeight.w500),
),
SizedBox(
width: 20,
),
Text(
// "Rs " + widget.pPrice,
"Rs 100",
style: TextStyle(
fontSize: 18,
fontWeight: FontWeight.w500,
// color: warning,
decoration: TextDecoration.lineThrough),
)
],
)
],
),
),
SizedBox(
height: 25,
),
Padding(
padding: const EdgeInsets.only(right: 20, left: 20),
child: Row(
children: <Widget>[
Text(
"Qty :",
style: TextStyle(
fontSize: 17, fontWeight: FontWeight.w500),
),
SizedBox(
width: 20,
),
Row(
children: <Widget>[
InkWell(
onTap: () {
if (quantity > 1) {
setState(() {
quantity = --quantity;
});
}
// minus here
},
child: Container(
width: 25,
height: 25,
decoration: BoxDecoration(
// border: Border.all(color: primary),
shape: BoxShape.circle),
child: Icon(
LineIcons.minus,
size: 15,
),
),
),
SizedBox(
width: 15,
),
Text(
quantity.toString(),
style: TextStyle(fontSize: 16),
),
SizedBox(
width: 15,
),
InkWell(
onTap: () {
setState(() {
quantity = ++quantity;
});
// minus here
},
child: Container(
width: 25,
height: 25,
decoration: BoxDecoration(
// border: Border.all(color: primary),
shape: BoxShape.circle),
child: Icon(
LineIcons.plus,
size: 15,
),
),
),
],
)
],
),
),
SizedBox(
height: 50,
),
InkWell(
onTap: () async {
---------------------------------------------
//here show my msg using dialog box
try {} on HttpException catch (e) {
print('hiii');
var errorMessage = 'Authentication Failed';
if (e.toString().contains(
'Product Succesfully Added to Cart')) {
errorMessage =
'Product Succesfully Added to Cart';
print(errorMessage);
_showerrorDialog(errorMessage);
}
} catch (error) {
var errorMessage = 'Please try again later';
_showerrorDialog(errorMessage);
}
------------------------------------------------
var qty = quantity.toString();
var plistId = widget.plistId;
print('pplistid' + plistId);
var uid = var_uid.toString();
var sid = var_sid.toString();
print('uuid' + uid);
print('ssid' + sid);
var response =
await add_to_cart_fn(qty, plistId, uid, sid);
print("rsp: " + response['status']);
},
// },
child: Padding(
padding: EdgeInsets.only(left: 20, right: 20),
child: Container(
height: 45,
width: double.infinity,
decoration: BoxDecoration(
color: kGreen,
borderRadius: BorderRadius.circular(30)),
child: Center(
child: Text(
"ADD TO CART",
style: TextStyle(
color: kWhite,
fontSize: 20,
),
),
),
),
),
),
SizedBox(height: 20.0),
// SomeMedicinePage(),
RelatedProductPage(plistId: widget.plistId)
],
);
})
: Center(
child: CircularProgressIndicator(
backgroundColor: Colors.white,
),
),
),
);
}
void _showerrorDialog(String message) {
showDialog(
context: context,
builder: (ctx) => AlertDialog(
title: Text(
'An Error Occurs',
style: TextStyle(color: Colors.blue),
),
content: Text(message),
actions: <Widget>[
FlatButton(
child: Text('Okay'),
onPressed: () => Navigator.of(context, rootNavigator: true).pop())
],
),
);
}
}

Answer 1

Found this answer (not mine):
is not an indication of a problem, it just indicates that code execution is not synchronous code executed line-by-line, but instead a callback from a completed Future started at some position in the callstack
Source :
https://stackoverflow.com/questions/60658945/asynchronous-suspension-in-stacktrace-output-in-flutter#:~:text=is%20not%20an,some%20position%20in%20the%20callstack.

Answer 2

wrap that api or platform specific code inside a try and catch block on catch (e){ do your stuff here error handling }