amount_localizer

Locale-aware amount formatter for Flutter, with a small native bridge that reads the device's true Region setting (iOS) / format-locale country (Android) — the setting that actually drives the numeric keyboard's decimal key.

Flutter's PlatformDispatcher.instance.locale only exposes the language locale. On an English-language iPhone with Region = Brazil, Dart sees en_US, but the numeric keyboard emits , for the decimal. This plugin closes that gap so amount fields format and parse against the correct locale.

What's inside

• AmountInputLocale — canonical enum of numeric formats (1,234.56 / 1.234,56 / 1 234,56 / Indian lakhs / …), with country and Locale resolvers.
• AmountLocalizer — cached intl-backed formatter with sensible banking defaults and a .localizedAmount extension on Object.
• DeviceRegionService — one call at app startup that reads the device region over a method channel and applies it to AmountInputLocale.regionOverride.

Setup

Add the dependency (from within this monorepo):

dependencies:
  amount_localizer:
    path: packages/amount_localizer

Initialize once, early in main() (before runApp):

import 'package:amount_localizer/amount_localizer.dart';

await DeviceRegionService.initializeAndApply();

Formatting

100.5.localizedAmount;                       // "100.50" on en_US, "100,50" on pt_BR
AmountLocalizer.format(1234.5);              // "1,234.50" / "1.234,50" / …
AmountLocalizer.tryFormat(json['amount']);   // safe; returns fallback ("—") on failure

Channel

Method channel: com.sri.amount_localizer/region, single method getFormatRegion returning an ISO 3166-1 alpha-2 country code (or null).