Unhandled Exception: FormatException: Invalid radix-10 number (at character 1) - html

Question

I was following this flutter beginner tutorial from net ninja here .But my timezone UTC +5:30 in Sri Lanka so i tried to add the half an hour but it keep getting this error that I cant fix. Please help me if you can!!.
Full Traceback error:
Performing hot restart...
Syncing files to device AOSP on IA Emulator...
Restarted application in 797ms.
E/flutter (31824): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: FormatException: Invalid radix-10 number (at character 1)
E/flutter (31824): 5:3
E/flutter (31824): ^
E/flutter (31824):
E/flutter (31824): #0 int._throwFormatException (dart:core-patch/integers_patch.dart:131:5)
E/flutter (31824): #1 int._parseRadix (dart:core-patch/integers_patch.dart:142:16)
E/flutter (31824): #2 int._parse (dart:core-patch/integers_patch.dart:100:12)
E/flutter (31824): #3 int.parse (dart:core-patch/integers_patch.dart:63:12)
E/flutter (31824): #4 WorldTime.getTime (package:world_time_app/services/world_time.dart:24:39)
E/flutter (31824): <asynchronous suspension>
E/flutter (31824): #5 _LoadingState.SetupWorldTime (package:world_time_app/pages/loading.dart:14:3)
E/flutter (31824): <asynchronous suspension>
E/flutter (31824):
Code :
import 'package:flutter/material.dart';
import 'package:http/http.dart';
import 'dart:convert';
class WorldTime{
String location;
String time;
String flag;
String url;
WorldTime({this.location, this.flag, this.url});
Future<void> getTime() async{
Response response = await get('https://www.worldtimeapi.org/api/timezone/$url');
Map data = jsonDecode(response.body.toString());
//print(data);
String datetime = data['datetime'];
String offset = data['utc_offset'].substring(2,5);
//print(dataTime);
//print(offset);
DateTime now = DateTime.parse(datetime);
now = now.add(Duration(hours: int.parse(offset)));
time = now.toString();
print(time);
}
}

Answer 1

In my case I was passing subroutes inside authority parameter, like this:
var response =
await http.get(Uri.https('https://favqs.com/api/quotes/', '4'), headers: {
'Content-Type': 'application/json',
'Authorization': "Token token='xxxxxxxxxxxxxxxx'",
});
but after removing https and moving /api/quotes/ in the second parameter, the issue got solved.
var response =
await http.get(Uri.https('favqs.com', '/api/quotes/4'), headers: {
'Content-Type': 'application/json',
'Authorization': "Token token='xxxxxxxxxxxxxxxx'",
});

Answer 2

You are trying to parse 5:3 as int, which causes the error.
The issue is in the substring that is returning an invalid number (5:3).
First you should do data['utc_offset'].substring(1,3) to get only the hour
And data['utc_offset'].substring(4,6) to get only the minutes.
After that, you can manipulate as you wish, like:
String offsetHours = data['utc_offset'].substring(1, 3);
String offsetMinutes = data['utc_offset'].substring(4, 6);
DateTime now = DateTime.parse(datetime);
now = now.add(Duration(
hours: int.parse(offsetHours),
minutes: int.parse(offsetMinutes)),
);