UI 관련 오류

1. The following assertion was thrown during performResize

The following assertion was thrown during performResize():
Horizontal viewport was given unbounded height.
Viewports expand in the cross axis to fill their container and constrain their children to match
their extent in the cross axis. In this case, a horizontal viewport was given an unlimited amount of
vertical space in which to expand.

위와 같은 오류 발생 원인 : Column 으로 감싼 ListView 에 설정된 높이가 없음 -> 제한 없는 높이값이 넘어옴

return Column(
  children: [
    const SizedBox(
      height: 200,
    ),
    makeList(snapshot), // => return ListView.separated( ~
  ],
);

Expanded(child: makeList(snapshot),) : 화면의 남는 공간을 차지하는 Widget 설정

2. The following ProgressEvent object was thrown resolving an image codec

The following ProgressEvent object was thrown resolving an image codec:
  [object ProgressEvent]

When the exception was thrown, this was the stack

Image provider:
  NetworkImage("https://image-comic.pstatic.net/webtoon/823999/thumbnail/thumbnail_IMAG21_db3ba875-37f1-4d05-a7c9-73d9bb43fc62.jpg",
  scale: 1.0)

Chrome 환경에서 Image.network Debug 테스트 시 위 오류 발생
~\toonflix\web\index.html > <script> > window.flutterWebRenderer = "html"; 추가

2-1. Exception caught by image resource service

════════ Exception caught by image resource service ════════════════════════════
HTTP request failed, statusCode: 403, https://image-comic.pstatic.net/webtoon/784248/thumbnail/thumbnail_IMAG21_20a8aca7-23d3-4bc0-9916-a31ebc884ca8.jpg

Android Mobile 환경에서 Image.network Debug 테스트 시 위 오류 발생
headers 추가

  headers: const {
    "User-Agent":
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36",
  },

2-2. Chrome + Android Mobile

Chrome + Android Mobile 환경에서 모두 이미지가 나오도록
main.dart > MyHttpOverrides() 추가

class MyHttpOverrides extends HttpOverrides {
  @override
  HttpClient createHttpClient(SecurityContext? context) {
    return super.createHttpClient(context)
      ..userAgent =
          'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36';
  }
}

void main() {
  HttpOverrides.global = MyHttpOverrides();
  runApp(const App());
}

3. BoxConstraints forces an infinite width.

case: Column > Row 안에 FractionallySizedBox 가 존재 (widthFactor: 1 => 100% 의 공간 차지)
box 가 무한대의 width 를 가지기 때문에 에러 발생
FractionallySizedBox 을 감싸는 Expanded 사용, 부모로서 크기를 결정하도록 함

BoxConstraints forces an infinite width.
These invalid constraints were provided to RenderDecoratedBox's layout() function by the following function, which probably computed the invalid constraints in question:
  RenderFractionallySizedOverflowBox.performLayout (package:flutter/src/rendering/shifted_box.dart:1171:14)
The offending constraints were: BoxConstraints(w=Infinity, 0.0<=h<=Infinity)

3-1. Horizontal viewport was given unbounded height

특정한 높이나 너비를 지정해주지 않아서 발생하는 오류

  SizedBox(
    width: MediaQuery.of(context).size.width,
    height: MediaQuery.of(context).size.height,
    child: const TabBarView(
      children: [

TabBarView 는 기본적으로 무한대의 크기를 가짐
- SizedBox 를 이용해 width, height 값 지정

Variable, Function 오류

1. The argument type 'void Function()' can't be assigned ~

The argument type 'void Function()' can't be assigned to the parameter type 'void Function(Timer)'
위의 경우는 Timer 를 파라미터로 할당해주지 않았다는 뜻
Timer 를 인자로 넣어주면 됨

2. Non-nullable instance field 'timer' must be initialized.

Timer timer; 의 경우, 초기화가 필요한데 초기화하지 않은 상태
미리 초기화 하지 않고 사용자가 버튼으 누를 때만 타이머가 생성되게 하려면 late variable modifier 사용
late Timer timer;

3. This class is marked as '@immutable' ~

This class (or a class that this class inherits from) is marked as '@immutable', but one or more of its instance fields aren't final: [클래스명].[변수명]
해당 변수를 final 로 설정해주면 됨 (immutable: 불변)

4. A nullable expression can't be used as an iterator in a for-in loop.

for (var webtoon in snapshot.data)
List 데이터가 null 일 수 있으므로 Null Safety 오류 발생
데이터가 있다고 확신하기 위해 ! 기호 사용하여 오류 제거 -> for (var webtoon in snapshot.data!)

5. The instance member 'webtoon' can's be accessed in an initializer.

The instance member 'webtoon' can's be accessed in an initializer. Try replacing the reference to the instance member with a different expression

final Future<WebtoonDetailModel> webtoonDetail = ApiService.getToonById(webtoon.id);

getToonById() 는 파라미터로 webtoon.id 를 받음
webtoonDetail 프로퍼티를 초기화할 때 webtoon 프로퍼티에 접근 불가
- StatelessWidget -> StatefulWidget 변경하여 해결
- 파라미터는 initState() 에서 widget.webtoon.id 형태로 사용

6. The method 'validate' can't be unconditionally invoked ~

The method 'validate' can't be unconditionally invoked because the receiver can be 'null'. Try making the call conditional (using '?.') or adding a null check to the target ('!').

final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

_formKey.currentState.validate();

currentState 가 없을 수도 있기 때문에 validate() 호출 불가
- 아래 두 가지 방법 중 택 1

if (_formKey.currentState != null) {
  _formKey.currentState!.validate(); // null 체크 후 확실히 존재함을 표시
}

_formKey.currentState?.validate();

7. (Failed assertion: 'items.length >= 2' : is not true.)

_AssertionError : 어떤 조건이 참이지 않을 때 발생하는 오류
items.length >= 2 : item 하위에 2개 이상의 item 이 존재해야 함

8. Don't user 'BuildContext's across async gaps.

Don't user 'BuildContext's across async gaps. Try rewriting the code to not use the 'BuildContext', or guard the user with a 'mounted' check.
async 환경에서 context 사용 시 발생하는 오류
mounted 체크하여 오류 제거

if (!mounted) return;
    
Navigator.push(
  context, (생략)
);

Const 오류

1. Use 'const' with the constructor

파란 밑줄과 함께 Use 'const' with the constructor to improve performance. 문구 확인(constant constructor 는 const 를 쓰는 걸 추천한다)
backgroundColor: const Color(0xFF181818), const SizedBox(...
const 로 만들어주는 것이 효과적, const 붙이면 밑줄 사라짐
Command Palette (Ctrl + Shift + P) > open user settings > settings.json 파일 열기
- editor.codeActionsOnSave 추가 : 자동으로 const 가 필요한 곳을 수정해줌
- dart.previewFlutterUiGuides 추가 : 부모-자식 식별을 위한 가이드라인 표시

  "[dart]": {
    "editor.tabSize": 2,
    "editor.insertSpaces": true,
    "editor.detectIndentation": false,
    "editor.suggest.insertMode": "replace",
    "editor.defaultFormatter": "Dart-Code.dart-code",
    "editor.inlayHints.enabled": "offUnlessPressed"
  },
  "editor.codeActionsOnSave": {
    "source.fixAll": true
  },
  "dart.previewFlutterUiGuides": true,

2. Arguments of a constant creation must be constant expressions

  child: const Padding(
    padding: EdgeInsets.symmetric(vertical: 20, horizontal: 50),
    child: Text(
      text, // 변수 text 를 받도록 하니, 이곳에서 빨간 밑줄 발생
      style: TextStyle(
        fontSize: 20,
        color: textColor,
      ),
    ),
  ),

위 코드에서 오류가 발생하는 이유
- Text 의 부모가 Padding 이고, Padding 은 const 생성자를 가지고 있음
- Text 가 const(상수)일 땐 가능한 이야기이나, 현재는 const 가 아닌 커스터마이징된 text 변수
const 를 지워준 후 저장, source.fixAll 에 의해 적절한 위치에 const 가 생성됨
즉, 컴파일 시 미리 알 수 있는 영역을 묶어 const 가 쓰여지는 것

작동 시 발생 문제

1. sleep()

로딩 중 화면 테스트를 위해 sleep() 을 사용했으나, 설정한 Duration 이후로도 sleep 상태에 있는 문제
- Async 코드에서는 Future.delayed() 사용

// In Async Code
await Future.delayed(Duration(seconds: 1));
// In Sync Code
sleep(Duration(seconds:1));

2. Set 'android:enableOnBackInvokedCallback="true"' in the application manifest.

android/app/src/main/AndroidManifest.xml 에 아래와 같이 추가
- Android 애플리케이션의 기본 설정을 정의하는 곳

    <application
        android:label="your_app_name"
        android:icon="@mipmap/ic_launcher"
        android:enableOnBackInvokedCallback="true"> <!-- 여기 추가 -->

VSCode > Terminal > 아래 명령어 입력

flutter clean
flutter pub get

Android 12(API 레벨 31) 이상의 기기에서 시스템의 뒤로가기 기능을 더 유연하고 통제 가능하게 사용하기 위함

3. ImagePicker().pickImage() - PlatformException

PlatformException (PlatformException(channel-error, Unable to establish connection on channel: "dev.flutter.pigeon.image_picker_android.ImagePickerApi.pickImages"., null, null))
image_picker: ^1.1.2 사용, final xfile = await ImagePicker().pickImage(); 실행하면 오류 발생
android/app/src/main/AndroidManifest.xml 에 아래와 같이 추가

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/> <!-- 여기 추가 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <!-- 여기 추가 -->
    <application
        android:label="RiFFest"

Flutter Error - ynjch97/YNJCH_WIKI GitHub Wiki

UI 관련 오류

1. The following assertion was thrown during performResize

2. The following ProgressEvent object was thrown resolving an image codec

2-1. Exception caught by image resource service

2-2. Chrome + Android Mobile

3. BoxConstraints forces an infinite width.

3-1. Horizontal viewport was given unbounded height

Variable, Function 오류

1. The argument type 'void Function()' can't be assigned ~

2. Non-nullable instance field 'timer' must be initialized.

3. This class is marked as '@immutable' ~

4. A nullable expression can't be used as an iterator in a for-in loop.

5. The instance member 'webtoon' can's be accessed in an initializer.

6. The method 'validate' can't be unconditionally invoked ~

7. (Failed assertion: 'items.length >= 2' : is not true.)

8. Don't user 'BuildContext's across async gaps.

Const 오류

1. Use 'const' with the constructor

2. Arguments of a constant creation must be constant expressions

작동 시 발생 문제

1. sleep()

2. Set 'android:enableOnBackInvokedCallback="true"' in the application manifest.

3. ImagePicker().pickImage() - PlatformException

참고 사이트 링크

Front-End

Back-End

Linux

ETC

다운로드

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Flutter Error - ynjch97/YNJCH_WIKI GitHub Wiki

UI 관련 오류

1. The following assertion was thrown during performResize

2. The following ProgressEvent object was thrown resolving an image codec

2-1. Exception caught by image resource service

2-2. Chrome + Android Mobile

3. BoxConstraints forces an infinite width.

3-1. Horizontal viewport was given unbounded height

Variable, Function 오류

1. The argument type 'void Function()' can't be assigned ~

2. Non-nullable instance field 'timer' must be initialized.

3. This class is marked as '@immutable' ~

4. A nullable expression can't be used as an iterator in a for-in loop.

5. The instance member 'webtoon' can's be accessed in an initializer.

6. The method 'validate' can't be unconditionally invoked ~

7. (Failed assertion: 'items.length >= 2' : is not true.)

8. Don't user 'BuildContext's across async gaps.

Const 오류

1. Use 'const' with the constructor

2. Arguments of a constant creation must be constant expressions

작동 시 발생 문제

1. sleep()

2. Set 'android:enableOnBackInvokedCallback="true"' in the application manifest.

3. ImagePicker().pickImage() - PlatformException

참고 사이트 링크

Front-End

Back-End

Linux

ETC

다운로드

⚠️ **GitHub.com Fallback** ⚠️

⚠️ GitHub.com Fallback ⚠️