The files in this directory are used to generate stock_strings.dart, which is used by the stocks application to look up localized message strings. The stocks app uses the Dart intl package.
Rebuilding everything requires two steps.
Create or update the English and Spanish localizations, stocks_en_US.arb, stocks_en.arb, and stocks_es.arb. See the ARB specification for more info.
With examples/stocks as the current directory, generate a messages_<locale>.dart for each stocks_<locale>.arb file, messages_all.dart, and stock_strings.dart with the following command:
dart ${FLUTTER_PATH}/dev/tools/localization/bin/gen_l10n.dart --arb-dir=lib/i18n \ --template-arb-file=stocks_en.arb --output-localization-file=stock_strings.dart \ --output-class=StockStrings
The StockStrings class creates a delegate that performs message lookups based on the locale of the device. In this case, the stocks app supports en, en_US, and es. Thus, the StockStringsEn and StockStringsEs classes extends StockStrings. StockStringsEnUs extends StockStringsEn. This allows StockStringsEnUs to fall back on messages in StockStringsEn.