Update system default language when switching.

app/src/main/java/org/thoughtcrime/securesms/util/dynamiclanguage/DynamicLanguageContextWrapper.java

@@ -2,8 +2,10 @@ package org.thoughtcrime.securesms.util.dynamiclanguage;
 
 import android.content.Context;
 import android.content.res.Configuration;
+import android.os.Build;
 
 import androidx.annotation.NonNull;
+import androidx.core.os.LocaleListCompat;
 
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
 
@@ -15,7 +17,14 @@ import java.util.Locale;
 public final class DynamicLanguageContextWrapper {
   private DynamicLanguageContextWrapper() {}
 
+  private static LocaleListCompat systemLocaleList = LocaleListCompat.getEmptyLocaleList();
+
   public static void prepareOverrideConfiguration(@NonNull Context context, @NonNull Configuration base) {
+    if (Build.VERSION.SDK_INT >= 24) {
+      systemLocaleList = LocaleListCompat.wrap(base.getLocales());
+    } else {
+      systemLocaleList = LocaleListCompat.create(base.locale);
+    }
     Locale newLocale = getUsersSelectedLocale(context);
 
     Locale.setDefault(newLocale);
@@ -25,7 +34,7 @@ public final class DynamicLanguageContextWrapper {
   @SuppressWarnings("deprecated")
   public static @NonNull Locale getUsersSelectedLocale(@NonNull Context context) {
     String language = TextSecurePreferences.getLanguage(context);
-    return LocaleParser.findBestMatchingLocaleForLanguage(language);
+    return LocaleParser.findBestMatchingLocaleForLanguage(language, systemLocaleList);
   }
 
   public static void updateContext(@NonNull Context base) {

app/src/main/java/org/thoughtcrime/securesms/util/dynamiclanguage/LocaleParser.java

@@ -1,8 +1,5 @@
 package org.thoughtcrime.securesms.util.dynamiclanguage;
 
-import android.content.res.Resources;
-import android.os.Build;
-
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.os.LocaleListCompat;
@@ -21,12 +18,13 @@ final class LocaleParser {
    * Given a language, gets the best choice from the apps list of supported languages and the
    * Systems set of languages.
    */
-  static @NonNull Locale findBestMatchingLocaleForLanguage(@Nullable String language) {
+  static @NonNull Locale findBestMatchingLocaleForLanguage(@Nullable String language, @NonNull LocaleListCompat systemLocaleList) {
     final Locale locale = LanguageString.parseLocale(language);
     if (appSupportsTheExactLocale(locale)) {
       return locale;
     } else {
-      return findBestSystemLocale();
+      final Locale firstMatch = systemLocaleList.getFirstMatch(BuildConfig.LANGUAGES);
+      return firstMatch != null ? firstMatch : Locale.ENGLISH;
     }
   }
 
@@ -36,24 +34,4 @@ final class LocaleParser {
     }
     return Arrays.asList(BuildConfig.LANGUAGES).contains(locale.toString());
   }
-
-  /**
-   * Get the first preferred language the app supports.
-   */
-  private static @NonNull Locale findBestSystemLocale() {
-    LocaleListCompat localeList;
-    if (Build.VERSION.SDK_INT < 24) {
-      localeList = LocaleListCompat.create(Resources.getSystem().getConfiguration().locale);
-    } else {
-      localeList = LocaleListCompat.getAdjustedDefault();
-    }
-
-    final Locale firstMatch = localeList.getFirstMatch(BuildConfig.LANGUAGES);
-
-    if (firstMatch != null) {
-      return firstMatch;
-    }
-
-    return Locale.ENGLISH;
-  }
 }

app/src/test/java/org/thoughtcrime/securesms/util/dynamiclanguage/LocaleParserTest.java

@@ -1,6 +1,10 @@
 package org.thoughtcrime.securesms.util.dynamiclanguage;
 
 import android.app.Application;
+import android.content.res.Resources;
+
+import androidx.core.os.ConfigurationCompat;
+import androidx.core.os.LocaleListCompat;
 
 import org.junit.Ignore;
 import org.junit.Test;
@@ -24,7 +28,7 @@ public final class LocaleParserTest {
   @Test
   public void findBestMatchingLocaleForLanguage_all_build_config_languages_can_be_resolved() {
     for (String lang : buildConfigLanguages()) {
-      Locale locale = LocaleParser.findBestMatchingLocaleForLanguage(lang);
+      Locale locale = LocaleParser.findBestMatchingLocaleForLanguage(lang, getSystemLocales());
       assertEquals(lang, locale.toString());
     }
   }
@@ -33,14 +37,14 @@ public final class LocaleParserTest {
   @Config(qualifiers = "fr")
   public void findBestMatchingLocaleForLanguage_a_non_build_config_language_defaults_to_device_value_which_is_supported_directly() {
     String unsupportedLanguage = getUnsupportedLanguage();
-    assertEquals(Locale.FRENCH, LocaleParser.findBestMatchingLocaleForLanguage(unsupportedLanguage));
+    assertEquals(Locale.FRENCH, LocaleParser.findBestMatchingLocaleForLanguage(unsupportedLanguage, getSystemLocales()));
   }
 
   @Test
   @Config(qualifiers = "en-rCA")
   public void findBestMatchingLocaleForLanguage_a_non_build_config_language_defaults_to_device_value_which_is_not_supported_directly() {
     String unsupportedLanguage = getUnsupportedLanguage();
-    assertEquals(Locale.CANADA, LocaleParser.findBestMatchingLocaleForLanguage(unsupportedLanguage));
+    assertEquals(Locale.CANADA, LocaleParser.findBestMatchingLocaleForLanguage(unsupportedLanguage, getSystemLocales()));
   }
 
   private static String getUnsupportedLanguage() {
@@ -52,4 +56,8 @@ public final class LocaleParserTest {
   private static List<String> buildConfigLanguages() {
     return Arrays.asList(BuildConfig.LANGUAGES);
   }
+
+  private static LocaleListCompat getSystemLocales() {
+    return ConfigurationCompat.getLocales(Resources.getSystem().getConfiguration());
+  }
 }