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fix: use the first available locale to decide directionality on Android#53417

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kainzhong wants to merge 1 commit intofacebook:mainfrom
kainzhong:fix_i18n_RTL
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fix: use the first available locale to decide directionality on Android#53417
kainzhong wants to merge 1 commit intofacebook:mainfrom
kainzhong:fix_i18n_RTL

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@kainzhong kainzhong commented Aug 21, 2025 •
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Summary:

On iOS, if the default locale is not supported in the app, it will fall back to the first available locale to decide if RTL layout should be enabled or not; however on Android, we use the default locale. So if the first locale is a RTL locale and not supported by the app on Android, the app will fall back to the first available locale which might not be RTL, but the layout would be decided as RTL according to the default locale.

Changelog:

[ANDROID] [FIXED] - use the first available locale instead of the default one to decide isDevicePreferredLanguageRTL

Test Plan:

I set my phone's locale to this order: Hebrew, English and enabled RTL layout:

import { I18nManager } from 'react-native';

I18nManager.allowRTL(true);
I18nManager.swapLeftAndRightInRTL(true);

Prior to my PR, the app would use RTL layout with English on Android which doesn't make much sense (iOS is LTR + English). With my PR Android app will behave exactly the same as the iOS app.

fix: use the first available language to decide directionality on And…
301330b 
…roid

Summary: on iOS, if the default locale is not supported in the app, it will fall back to the first available locale to decide if RTL layout should be enabled or not; however on Android, we use the default locale. So if the first locale is a RTL locale and not supported by the app on Android, the app will fall back to the first available locale which might not be RTL, but the layout would be decided as RTL according to the default locale.
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meta-cla bot commented Aug 21, 2025

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kainzhong commented Aug 21, 2025

(I just signed CLA

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Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!

@meta-cla meta-cla bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Aug 21, 2025
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facebook-github-bot commented Aug 22, 2025

@zeyap has imported this pull request. If you are a Meta employee, you can view this in D80821903.

@facebook-github-bot facebook-github-bot added the Merged This PR has been merged. label Aug 28, 2025
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react-native-bot commented Aug 28, 2025

This pull request was successfully merged by Kaining Zhong in a03780d

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facebook-github-bot commented Aug 28, 2025

@zeyap merged this pull request in a03780d.

@mukti107
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mukti107 commented Dec 19, 2025

this causes the issue, now changing the app language from englist to arabic still forces LTR instead of RTL.

Locale.getAvailableLocales()[0]
This gets the first locale in the list of ALL available locales installed on the device, not the current/preferred language. This is incorrect.

It should be using one of these instead:
Locale.getDefault() – the system's default locale
context.resources.configuration.locales[0] – the app's current locale (respects per-app language on Android 13+)

@mukti107 mukti107 mentioned this pull request Dec 19, 2025
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@kainzhong kainzhong mentioned this pull request Dec 26, 2025
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kainzhong commented Dec 26, 2025

@mukti107 I'm terribly sorry. I made a new PR #54986 and changed to your proposed method to decide the directionality. Please take a look and confirm if that fix your issue. Thanks a lot!

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