flutter-setup-localization

Add the flutter_localizations and intl packages to pubspec.yaml, set generate: true under the flutter section, and create an l10n.yaml file pointing to your ARB directory. Then register AppLocalizations.delegate and the global delegates in your MaterialApp.

Define strings as key-value pairs in a template ARB file like app_en.arb, with metadata entries prefixed by @ for descriptions and placeholders. Create matching files per locale such as app_es.arb, then run flutter pub get to generate the AppLocalizations class.

Use ICU plural syntax inside the ARB value, such as {count, plural, =0{no items} other{{count} items}}, and declare the count placeholder with type num in the metadata. The other case is mandatory for the message to compile.

AppLocalizations.of(context) returns null when the calling widget is not a descendant of MaterialApp or when the localization delegates are not registered. Verify localizationsDelegates and supportedLocales are set, and run flutter pub get to regenerate the classes.

Yes, ARB files support placeholders using curly brace syntax like Hello {userName}, with the parameter type and example declared in the placeholders metadata object. The generated code produces a typed method accepting that parameter.