I could not decode http response into UTF-8 by Flutter - ios

Question

In the process of developing iOS application with Flutter, there is a problem that HTTP response cannot be decoded with UTF-8, and I would like to solve it.
The Android Pixel 2 emulator was able to decode without any problems, so I think it is an iOS-specific problem.
The result is the result of running using tPhone 12 Pro Max emulator. (iOS Deployment Target=9.0)
This issue is that content of decoded_body_byte is null.
import 'dart:async';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:html/dom.dart' as dom;
import 'package:http/http.dart' as http;
import 'package:charset_converter/charset_converter.dart';
import 'package:flutter_user_agent/flutter_user_agent.dart';
// skip
String userAgent;
try {
userAgent = await FlutterUserAgent.getPropertyAsync('userAgent');
print("userAgent: ${userAgent}");
} on PlatformException {
userAgent = '<error>';
}
var response = await http.Client().get(Uri.parse("http://news4vip.livedoor.biz/archives/52385788.html"), headers: {'User-Agent': userAgent});
print("Response status: ${response.statusCode}");
print("response.headers: ${response.headers['content-type']}");
String decoded_body_byte = await CharsetConverter.decode("UTF-8", response.bodyBytes);
print("decoded_body_byte: ${decoded_body_byte}"); // ここの結果がnullになってしまうことが問題になっています。
Uint8List encoded = await CharsetConverter.encode("UTF-8", "【画像】中日「かっこいい」今季のユニホーム発表ｗｗｗ");
print("encoded.length: ${encoded.length}");
String decoded_body_byte_only_title = await CharsetConverter.decode("UTF-8", response.bodyBytes.sublist(71, 71 + 78));
print("decoded_body_byte_only_title: ${decoded_body_byte_only_title}");
The following is the output result of the above code.
2021-01-23 17:09:29.964984+0900 Runner[89036:14458916] flutter: userAgent: CFNetwork/1209 Darwin/20.2.0 (iPhone iOS/14.3)
2021-01-23 17:09:30.187131+0900 Runner[89036:14458916] flutter: Response status: 200
2021-01-23 17:09:30.190547+0900 Runner[89036:14458916] flutter: response.headers: text/html; charset=utf-8
2021-01-23 17:09:30.195755+0900 Runner[89036:14458916] flutter: decoded_body_byte: null
2021-01-23 17:09:30.197368+0900 Runner[89036:14458916] flutter: encoded.length: 78
2021-01-23 17:09:30.198128+0900 Runner[89036:14458916] flutter: decoded_body_byte_only_title: 【画像】中日「かっこいい」今季のユニホーム発表ｗｗｗ
Below is the output result of $ flutter doctor.
I would appreciate it if you could answer.
% flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 1.22.5, on macOS 11.1 20C69 darwin-x64, locale ja-JP)
[!] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
! Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licenses
[✓] Xcode - develop for iOS and macOS (Xcode 12.3)
[!] Android Studio (version 4.1)
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
[✓] VS Code (version 1.52.1)
[✓] Connected device (2 available)
! Doctor found issues in 2 categories.

Answer 1

I can decode target web page using below Plugin instead of charset converter.
Maybe this http response included illegal character.
https://api.flutter.dev/flutter/dart-convert/Utf8Codec/decode.html
final decoded = Utf8Decoder(allowMalformed: true).convert(response.bodyBytes);