auto_l10n 0.1.0

Automatic Flutter app translation with zero code changes. One line in main.dart. Supports DeepL, MyMemory, Lingva, Google Translate, and custom translators.

example/lib/main.dart

import 'package:auto_l10n/auto_l10n.dart';
import 'package:flutter/material.dart';

void main() {
  AutoL10nBinding.ensureInitialized(
    provider: TranslationProvider.mymemory,
    targetLocale: const Locale('es'),
  );
  runApp(const ExampleApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true, colorSchemeSeed: Colors.indigo),
      home: const HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  static const _locales = {
    'en': 'English',
    'ru': 'Russian',
    'de': 'German',
    'fr': 'French',
    'ja': 'Japanese',
    'es': 'Spanish',
    'zh': 'Chinese',
  };

  String _selected = 'es'; // must match targetLocale in main()

  void _onLocaleChanged(String code) {
    setState(() => _selected = code);
    AutoL10nBinding.setLocale(Locale(code));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Hello World')),
      body: Padding(
        padding: const EdgeInsets.all(24),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            // Locale picker
            Wrap(
              spacing: 8,
              runSpacing: 8,
              children:
                  _locales.entries.map((e) {
                    final isActive = e.key == _selected;
                    return ChoiceChip(
                      label: Text(e.value),
                      selected: isActive,
                      onSelected: (_) => _onLocaleChanged(e.key),
                    );
                  }).toList(),
            ),
            const SizedBox(height: 8),
            Text(
              'Current locale: $_selected',
              style: Theme.of(context).textTheme.bodySmall,
            ),
            const Divider(height: 32),

            // Translatable content
            const Text('Welcome to auto_l10n'),
            const SizedBox(height: 12),
            const Text('This text is translated automatically'),
            const SizedBox(height: 12),
            const Text('No API key required for this demo'),
            const SizedBox(height: 12),
            const Text('Add one line to main.dart and you are done'),
            const SizedBox(height: 24),
            const ElevatedButton(onPressed: null, child: Text('Submit')),
            const SizedBox(height: 32),
            const Divider(height: 1),
            const SizedBox(height: 16),
            Text(
              'Example: add to main.dart',
              style: Theme.of(context).textTheme.titleSmall,
            ),
            const SizedBox(height: 8),
            Container(
              width: double.infinity,
              padding: const EdgeInsets.all(12),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.surfaceContainerHighest,
                borderRadius: BorderRadius.circular(8),
              ),
              child: SelectableText.rich(
                _buildHighlightedCode(context, _exampleCode),
                style: Theme.of(context).textTheme.bodySmall?.copyWith(
                  fontFamily: 'monospace',
                  fontFamilyFallback: const ['monospace'],
                  fontSize: 12,
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  static const String _exampleCode = r'''
void main() {
  AutoL10nBinding.ensureInitialized(
    provider: TranslationProvider.DeepL,
    apiKey: 'YOUR_DEEPL_KEY',
    targetLocale: const Locale('es'),  // optional: defaults to device locale
  );
  runApp(const MyApp());
}
''';

  static const _keywords = {
    'void',
    'main',
    'const',
    'runApp',
    'return',
    'class',
    'extends',
    'provider',
    'translator',
  };

  TextSpan _buildHighlightedCode(BuildContext context, String code) {
    final theme = Theme.of(context);
    final baseStyle = theme.textTheme.bodySmall!.copyWith(
      fontFamily: 'monospace',
      fontFamilyFallback: const ['monospace'],
      fontSize: 12,
      color: theme.colorScheme.onSurface,
    );
    final keywordColor =
        theme.brightness == Brightness.dark
            ? const Color(0xFF81A2BE)
            : const Color(0xFF0550AE);
    final stringColor =
        theme.brightness == Brightness.dark
            ? const Color(0xFFB5BD68)
            : const Color(0xFF0D6938);
    final typeColor =
        theme.brightness == Brightness.dark
            ? const Color(0xFF8ABEB7)
            : const Color(0xFF953800);
    final punctuationColor = theme.colorScheme.onSurface.withValues(alpha: 0.8);

    final spans = <TextSpan>[];
    var i = 0;
    while (i < code.length) {
      if (code[i] == "'" || code[i] == '"') {
        final quote = code[i];
        final start = i;
        i++;
        while (i < code.length && code[i] != quote) {
          if (code[i] == '\\') i++;
          i++;
        }
        if (i < code.length) i++;
        spans.add(
          TextSpan(
            text: code.substring(start, i),
            style: baseStyle.copyWith(color: stringColor),
          ),
        );
        continue;
      }
      if (_isLetterOrUnderscore(code[i])) {
        final start = i;
        while (i < code.length && _isWordChar(code[i])) {
          i++;
        }
        final word = code.substring(start, i);
        if (_keywords.contains(word)) {
          spans.add(
            TextSpan(
              text: word,
              style: baseStyle.copyWith(color: keywordColor),
            ),
          );
        } else if (word.startsWith(RegExp(r'[A-Z]'))) {
          spans.add(
            TextSpan(text: word, style: baseStyle.copyWith(color: typeColor)),
          );
        } else {
          spans.add(TextSpan(text: word, style: baseStyle));
        }
        continue;
      }
      if (code[i] == '(' ||
          code[i] == ')' ||
          code[i] == '{' ||
          code[i] == '}' ||
          code[i] == ',' ||
          code[i] == ';' ||
          code[i] == '.') {
        spans.add(
          TextSpan(
            text: code[i],
            style: baseStyle.copyWith(color: punctuationColor),
          ),
        );
        i++;
        continue;
      }
      final start = i;
      while (i < code.length &&
          code[i] != "'" &&
          code[i] != '"' &&
          !_isLetterOrUnderscore(code[i]) &&
          code[i] != '(' &&
          code[i] != ')' &&
          code[i] != '{' &&
          code[i] != '}' &&
          code[i] != ',' &&
          code[i] != ';' &&
          code[i] != '.') {
        i++;
      }
      if (start < i) {
        spans.add(TextSpan(text: code.substring(start, i), style: baseStyle));
      }
    }
    return TextSpan(children: spans, style: baseStyle);
  }

  static bool _isLetterOrUnderscore(String c) {
    if (c.isEmpty) return false;
    final u = c.codeUnitAt(0);
    return (u >= 65 && u <= 90) || (u >= 97 && u <= 122) || u == 95;
  }

  static bool _isWordChar(String c) {
    if (c.isEmpty) return false;
    final u = c.codeUnitAt(0);
    return _isLetterOrUnderscore(c) || (u >= 48 && u <= 57);
  }
}