Flutter Mobile Development · 강의

ARB 파일 및 gen_l10n 현지화 작업 흐름

flutter_localizations와 gen_l10n 파이프라인을 설정해 타입이 지정된 번역을 생성합니다.

ARB 파일 및 gen_l10n 현지화 작업 흐름은(는) CoddyKit의 무료 Flutter Mobile Development 강의입니다. 이것은 4개 중 1번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Flutter Mobile Development 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Flutter Mobile Development 강의에는 총 4개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

Step 1: Why gen_l10n + dependencies

Hard-coding strings like Text('Welcome') makes an app impossible to translate. Flutter's official solution is gen_l10n: you write translations in ARB (Application Resource Bundle, a JSON format) files, and the build tool generates a typed Dart class so typos become compile-time errors.

Two pieces are required in pubspec.yaml. The flutter_localizations SDK package supplies Material/Cupertino/Widgets translations, and the generate: true flag turns on the gen_l10n build step.

intl is pulled in because generated code uses it for plurals and dates.
After editing, run flutter pub get.

dependencies:
  flutter:
    sdk: flutter
  flutter_localizations:
    sdk: flutter
  intl: any

flutter:
  generate: true

Step 2: l10n.yaml config

Create an l10n.yaml file at the project root. It tells gen_l10n where your ARB files live and what to name the generated class.

arb-dir — folder holding the .arb files.
template-arb-file — the source-of-truth locale that defines keys and metadata.
output-localization-file — name of the generated Dart file.
output-class — the class name you import in code.

# l10n.yaml
arb-dir: lib/l10n
template-arb-file: app_en.arb
output-localization-file: app_localizations.dart
output-class: AppLocalizations

Step 3: The template ARB file

The template locale (here app_en.arb) defines every key. Each key maps to a translated value. Keys starting with @ are metadata: they describe the entry but produce no string.

@@locale declares which locale this file is.
@welcome can carry a description to help translators.

The filename pattern is app_<localeCode>.arb.

{
  "@@locale": "en",
  "welcome": "Welcome",
  "@welcome": {
    "description": "Greeting shown on the home screen"
  },
  "settings": "Settings"
}

Step 4: A translated ARB file

For each additional language, add a sibling file with the same keys but translated values. Metadata (the @ keys) is only required in the template; translations may omit it.

Here app_tr.arb provides Turkish strings.
Missing keys fall back to the template locale, so keep the template complete.

{
  "@@locale": "tr",
  "welcome": "Hoş geldiniz",
  "settings": "Ayarlar"
}

Step 5: Generate the code

Code generation runs automatically during flutter run or flutter build when generate: true is set. You can also force it with flutter gen-l10n.

Output lands in .dart_tool/flutter_gen/gen_l10n/ by default.
The generated AppLocalizations class exposes one getter per key.
Add the generated path to your IDE's import suggestions; do not commit generated files.

Step 6: Wire into MaterialApp

Register the generated delegates and supported locales on MaterialApp. AppLocalizations.localizationsDelegates bundles your delegate plus the Material/Widgets/Cupertino ones, and supportedLocales lists what you ship.

Flutter picks the best match between the device locale and supportedLocales.
If none match, the first entry in supportedLocales is used.

import 'package:flutter/material.dart';
import 'package:flutter_gen/gen_l10n/app_localizations.dart';

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      localizationsDelegates: AppLocalizations.localizationsDelegates,
      supportedLocales: AppLocalizations.supportedLocales,
      home: const HomeScreen(),
    );
  }
}

Step 7: Read a string

Inside a widget you fetch the localized instance with AppLocalizations.of(context) and read a getter. The call is null only if the delegates are missing, so the common idiom uses !.

Each key from the ARB becomes a strongly-typed getter.
Rename a key in the ARB and every wrong usage fails to compile.

import 'package:flutter/material.dart';
import 'package:flutter_gen/gen_l10n/app_localizations.dart';

class HomeScreen extends StatelessWidget {
  const HomeScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context)!;
    return Scaffold(
      appBar: AppBar(title: Text(l10n.settings)),
      body: Center(child: Text(l10n.welcome)),
    );
  }
}

Step 8: Placeholders

To inject values, declare placeholders in the template metadata. The value uses {name} syntax, and gen_l10n turns the getter into a method.

Each placeholder needs a type (e.g. String, int, DateTime).
The generated method signature follows the placeholder order.

{
  "@@locale": "en",
  "greeting": "Hello, {name}!",
  "@greeting": {
    "description": "Personalized greeting",
    "placeholders": {
      "name": { "type": "String" }
    }
  }
}

Step 9: Call a placeholder method

Because greeting takes an argument, the generated member is a method, not a getter. You pass the value at the call site.

l10n.greeting('Ada') returns "Hello, Ada!".
Types are enforced: passing an int where a String is expected fails to compile.

Widget buildGreeting(BuildContext context, String userName) {
  final l10n = AppLocalizations.of(context)!;
  return Text(l10n.greeting(userName));
}

Step 10: Plurals with ICU

ARB supports ICU message syntax for plurals. A {count, plural, ...} block selects the right wording per language. Declare the placeholder as num (or int).

=0, one, and other are common categories.
# is replaced by the formatted number.
Different locales have different plural rules — ICU handles them automatically.

{
  "itemCount": "{count, plural, =0{No items} one{1 item} other{{count} items}}",
  "@itemCount": {
    "placeholders": {
      "count": { "type": "int" }
    }
  }
}

Step 11: A plain-Dart formatter

The selection logic ICU performs is just rules over a number. Here is a tiny standalone Dart program that mimics English plural selection — useful for understanding what gen_l10n generates under the hood.

Real apps use the generated method; this is only for intuition.

String itemCount(int count) {
  if (count == 0) return 'No items';
  if (count == 1) return '1 item';
  return '$count items';
}

void main() {
  for (final n in [0, 1, 5]) {
    print(itemCount(n));
  }
}

Quick Check

You added a new key logout only to app_en.arb but forgot it in app_tr.arb. A Turkish-locale user opens the screen. What happens?

Recap

You built the full Flutter localization pipeline:

Added flutter_localizations + intl and set generate: true.
Configured l10n.yaml (arb-dir, template, output class).
Wrote a template ARB plus per-locale translations.
Let gen_l10n create the typed AppLocalizations class.
Registered localizationsDelegates and supportedLocales, then read strings via AppLocalizations.of(context)!.
Used placeholders for dynamic values and ICU plurals for count-aware text.

The payoff: translations are type-checked, missing template keys are caught early, and translators work in a clean JSON format.

자주 묻는 질문

“ARB 파일 및 gen_l10n 현지화 작업 흐름” 강의는 무료인가요?

네 — “ARB 파일 및 gen_l10n 현지화 작업 흐름” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Flutter Mobile Development 강의 전체를 잠금 해제할 수 있습니다. Flutter Mobile Development 강의에는 총 4개의 강의가 포함되어 있습니다.

“ARB 파일 및 gen_l10n 현지화 작업 흐름”에서 뭘 배우나요?

flutter_localizations와 gen_l10n 파이프라인을 설정해 타입이 지정된 번역을 생성합니다. 브라우저에서 직접 실행하는 실습 코드로 Flutter Mobile Development을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.

Flutter Mobile Development을(를) 시작하는 데 경험이 필요한가요?

사전 경험은 필요하지 않습니다. CoddyKit의 Flutter Mobile Development은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 1번째 강의입니다.

“ARB 파일 및 gen_l10n 현지화 작업 흐름” 강의는 얼마나 걸리나요?

대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.

이 Flutter Mobile Development 강의에서 코드를 작성하고 실행할 수 있나요?

네. 모든 Flutter Mobile Development 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.

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