Support Per-app language preferences #579

314systems · 2025-12-29T08:18:55Z

Summary

Support Per-app language preferences

What does this implement/fix?

Support Per-app language preferences.

Does this close any issues?

Closes [Feature] Support Per-app language preferences #577

How was this tested?

Devices / OS (e.g. Android 13 emulator, Pixel 6):
Platform / Build variant (e.g. debug/release):
Toolchain / Gradle / SDK version(s):
Steps to reproduce / test (provide exact steps so reviewers can verify):

Example test commands:

./gradlew ktlintCheck

Checklist (required before marking ready)

I added or updated unit tests (see app/src/test/)
I followed the project's coding style (ktlint) and formatting
I ran lint and addressed or documented any warnings
CI checks pass (unit tests, coverage, lint)
No sensitive data, keys, or secrets are included

Additional context

Screenshots, logs, or other context that helps reviewers understand the change.
Migration notes or compatibility considerations (if applicable).

…ales

Copilot

Pull request overview

This PR implements per-app language preferences by migrating from a custom locale management approach to Android's native AppCompatDelegate API. The changes align with Android's modern language preference system introduced in API 33+, enabling users to select a language specifically for this app independent of the system language.

Key changes:

Migrated from manual context creation with custom locale to AppCompatDelegate.setApplicationLocales()
Removed language change tracking from MainReload since AppCompat handles activity recreation automatically
Updated locale utility functions to use BCP-47 language tags and improved Chinese locale handling with script-based differentiation

Reviewed changes

Copilot reviewed 37 out of 38 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
app/src/main/kotlin/com/vrem/wifianalyzer/MainActivity.kt	Removed attachBaseContext override; added onSharedPreferenceChanged logic to handle language changes via AppCompatDelegate; added syncLanguage call in onCreate
app/src/main/kotlin/com/vrem/wifianalyzer/MainReload.kt	Removed language locale tracking since AppCompat handles locale changes automatically
app/src/main/kotlin/com/vrem/wifianalyzer/settings/Settings.kt	Replaced languageLocale() with appLocale() using AppCompatDelegate.getApplicationLocales(); added syncLanguage() method
app/src/main/kotlin/com/vrem/wifianalyzer/settings/LanguagePreference.kt	Updated to support "System default" option with empty string tag; refactored data() to accept Context
app/src/main/kotlin/com/vrem/wifianalyzer/settings/CountryPreference.kt	Updated method call from languageLocale() to appLocale(); renamed utility function reference
app/src/main/kotlin/com/vrem/wifianalyzer/wifi/channelavailable/ChannelAvailableFragment.kt	Updated method call from languageLocale() to appLocale()
app/src/main/kotlin/com/vrem/wifianalyzer/vendor/model/VendorService.kt	Changed uppercase() to use Locale.ROOT for locale-independent string operations
app/src/main/kotlin/com/vrem/util/LocaleUtils.kt	Major refactor: added BCP-47 language tag support, improved Chinese locale handling with script detection, renamed functions for clarity, removed legacy underscore format generation
app/src/main/kotlin/com/vrem/util/CompatUtils.kt	Removed createContext() extension function no longer needed with AppCompat
app/src/main/kotlin/com/vrem/util/StringUtils.kt	Added titlecaseFirst() extension function for proper title casing of locale display names
app/src/main/AndroidManifest.xml	Added AppLocalesMetadataHolderService configuration with autoStoreLocales enabled
app/src/main/res/resources.properties	Added unqualifiedResLocale=en-US to specify base locale for resources
app/build.gradle	Added generateLocaleConfig=true for automatic locale configuration generation
app/src/main/res/values*/strings.xml	Added "system_default" string translations in all supported languages
app/src/test/kotlin/*/Test.kt	Updated tests to reflect API changes: renamed method calls, updated locale handling tests, removed language tracking tests

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Copilot · 2026-01-01T09:29:58Z

app/src/main/kotlin/com/vrem/util/LocaleUtils.kt

+
+fun toLanguageTag(locale: Locale): String = locale.toLanguageTag()
+
+fun Locale.toSupportedLocaleTag(): String = findByLanguageTag(this.toLanguageTag()).toLanguageTag()


The toSupportedLocaleTag() extension function performs a round-trip conversion: it converts the locale to a language tag, calls findByLanguageTag which parses it back to a Locale, and then converts that back to a language tag. This is inefficient and could be simplified. Consider creating a direct method that maps a Locale to its supported equivalent without the intermediate string conversions, or at least add a comment explaining why this approach is necessary if there's a specific reason for it.

Copilot · 2026-01-01T09:29:58Z

app/src/main/kotlin/com/vrem/util/LocaleUtils.kt

+private val countriesLocales: SortedMap<String, Locale> =
+    availableLocales


The initialization of countriesLocales on line 28 uses currentLocale which calls Locale.getDefault() at initialization time. This means the map keys will be capitalized using the default locale at app startup. If the user later changes the app's language preference, the map keys will still be in the original locale's capitalization, which could cause inconsistencies in country name display. Consider making countriesLocales a function that computes the map dynamically, or ensure this is the intended behavior and document it.

Suggested change

private val countriesLocales: SortedMap<String, Locale> =

availableLocales

private val countriesLocales: SortedMap<String, Locale>

get() = availableLocales

Copilot · 2026-01-01T09:29:59Z

app/src/main/kotlin/com/vrem/wifianalyzer/settings/Settings.kt

+    fun syncLanguage() {
+        val appLocaleTag = appLocale().toSupportedLocaleTag()
+        if (appLocaleTag != repository.string(R.string.language_key, "")) {
+            repository.save(R.string.language_key, appLocaleTag)
+        }
    }


The new syncLanguage() method in Settings class lacks test coverage. This method is called during app startup and handles syncing the application locale from AppCompatDelegate back to SharedPreferences. Consider adding a test case that verifies this synchronization behavior, especially since it involves interaction between the Android framework (AppCompatDelegate) and the app's settings storage.

Copilot · 2026-01-01T09:29:59Z

app/src/main/kotlin/com/vrem/wifianalyzer/MainActivity.kt

+        val languageKey = getString(R.string.language_key)
+        if (key == languageKey) {
+            val languageTag = sharedPreferences.getString(languageKey, "")
+            val locales =
+                languageTag
+                    ?.takeIf { it.isNotEmpty() }
+                    ?.let(LocaleListCompat::forLanguageTags)
+                    ?: LocaleListCompat.getEmptyLocaleList()
+
+            AppCompatDelegate.setApplicationLocales(locales)
+        }


The new language preference change handling logic in onSharedPreferenceChanged (lines 119-129) lacks test coverage. This is critical functionality that calls AppCompatDelegate.setApplicationLocales() when the language preference changes. Consider adding test cases that verify the locale is correctly set when the language_key preference changes, including edge cases like empty strings and null values.

Copilot · 2026-01-01T09:29:59Z

app/src/main/kotlin/com/vrem/util/StringUtils.kt


 fun String.toCapitalize(locale: Locale): String = this.replaceFirstChar { word -> word.uppercase(locale) }
+
+fun String.titlecaseFirst(locale: Locale): String = replaceFirstChar { it.titlecase(locale) }


The new titlecaseFirst() extension function in StringUtils.kt lacks test coverage. This function is used to capitalize language display names in the language preference list. Consider adding test cases to verify its behavior with various inputs, including edge cases like empty strings, strings with different Unicode characters, and strings in different locales to ensure proper title casing.

Copilot · 2026-01-01T09:29:59Z

app/src/main/kotlin/com/vrem/wifianalyzer/MainActivity.kt

+                    ?.takeIf { it.isNotEmpty() }
+                    ?.let(LocaleListCompat::forLanguageTags)
+                    ?: LocaleListCompat.getEmptyLocaleList()
+


The language preference change handling logic could benefit from a comment explaining the flow. Specifically, it would be helpful to document that when the language preference is changed, AppCompatDelegate.setApplicationLocales() is called, which triggers a configuration change and activity recreation, so the syncLanguage() call in onCreate will sync the preference value back to shared preferences after the recreation.

Suggested change

// When the language preference changes, update the application locales.

// This call triggers a configuration change and causes the activity to be recreated.

// After recreation, onCreate() is invoked again and settings.syncLanguage() is called,

// which syncs the effective language value back to shared preferences.

Copilot · 2026-01-01T09:30:00Z

app/src/main/kotlin/com/vrem/wifianalyzer/settings/Settings.kt

+    fun syncLanguage() {
+        val appLocaleTag = appLocale().toSupportedLocaleTag()
+        if (appLocaleTag != repository.string(R.string.language_key, "")) {
+            repository.save(R.string.language_key, appLocaleTag)
+        }
    }


The syncLanguage method could create an unnecessary write to SharedPreferences on every app startup when the locale hasn't changed. Consider adding a check to only save if the value in preferences is different from the current appLocaleTag. The current implementation compares against an empty string default, which means if the preference is not set (null), it will still match an empty string and not save, but if the preference was previously set to a value that matches appLocaleTag, it will still perform the comparison on every startup. Consider optimizing by reading the current value first before saving.

314systems and others added 13 commits December 26, 2025 23:07

enable locale config generation

99f1b5a

add AppLocalesMetadataHolderService to manifest

943a4dd

refactor LocaleUtils and update settings references

83771c1

add system_default string to translations

96ec463

update locale utils and language preference

6d5cc0a

refactor locale handling to use AppCompatDelegate for application loc…

4758f5d

…ales

update LocaleUtils and refactor language preference tests

730dc4f

reformat

402dcca

Merge branch 'main' into lang

dc91a1e

Merge branch 'main' into lang

a411b65

reorder and update supported locales in LocaleUtils and LocaleUtilsTest

c3f3466

rename variable

8ce2941

remove createContext from CompatUtils and CompatUtilsTest

feaa2c8

314systems force-pushed the lang branch from 8229c34 to 4d2ae95 Compare January 1, 2026 09:02

add support for Chinese language tags and update tests

286c209

314systems force-pushed the lang branch from 4d2ae95 to 286c209 Compare January 1, 2026 09:06

314systems marked this pull request as ready for review January 1, 2026 09:25

Copilot AI review requested due to automatic review settings January 1, 2026 09:25

Copilot started reviewing on behalf of 314systems January 1, 2026 09:25 View session

Copilot AI reviewed Jan 1, 2026

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Support Per-app language preferences #579

Support Per-app language preferences #579

314systems commented Dec 29, 2025 •

edited by VREMSoftwareDevelopment

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		fun toLanguageTag(locale: Locale): String = locale.toLanguageTag()

		fun Locale.toSupportedLocaleTag(): String = findByLanguageTag(this.toLanguageTag()).toLanguageTag()

		private val countriesLocales: SortedMap<String, Locale> =
		availableLocales


		fun String.toCapitalize(locale: Locale): String = this.replaceFirstChar { word -> word.uppercase(locale) }

		fun String.titlecaseFirst(locale: Locale): String = replaceFirstChar { it.titlecase(locale) }

+            // When the language preference changes, update the application locales.
+            // This call triggers a configuration change and causes the activity to be recreated.
+            // After recreation, onCreate() is invoked again and settings.syncLanguage() is called,
+            // which syncs the effective language value back to shared preferences.

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Summary

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314systems commented Dec 29, 2025 •

edited by VREMSoftwareDevelopment

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