Resolve switching languages problem in settings fragment

app/src/main/java/fr/free/nrw/commons/settings/SettingsFragment.java

@@ -146,7 +146,7 @@ public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
             appUiLanguageListPreference.setSummary(Locale.getDefault().getDisplayLanguage());
         } else {
             // If any language is selected by user previously, use it
-            Locale defLocale = new Locale(languageCode);
+            Locale defLocale = createLocale(languageCode);
             appUiLanguageListPreference.setSummary((defLocale).getDisplayLanguage(defLocale));
         }
         appUiLanguageListPreference.setOnPreferenceClickListener(new OnPreferenceClickListener() {
@@ -167,7 +167,7 @@ public boolean onPreferenceClick(Preference preference) {
             descriptionLanguageListPreference.setSummary(Locale.getDefault().getDisplayLanguage());
         } else {
             // If any language is selected by user previously, use it
-            Locale defLocale = new Locale(languageCode);
+            Locale defLocale = createLocale(languageCode);
             descriptionLanguageListPreference.setSummary(defLocale.getDisplayLanguage(defLocale));
         }
         descriptionLanguageListPreference.setOnPreferenceClickListener(new OnPreferenceClickListener() {
@@ -361,7 +361,7 @@ public void onItemClick(AdapterView<?> adapterView, View view, int i,
                 }
                 recentLanguagesDao.addRecentLanguage(new Language(languageName, languageCode));
                 saveLanguageValue(languageCode, keyListPreference);
-                Locale defLocale = new Locale(languageCode);
+                Locale defLocale = createLocale(languageCode);
                 if(keyListPreference.equals("appUiDefaultLanguagePref")) {
                     appUiLanguageListPreference.setSummary(defLocale.getDisplayLanguage(defLocale));
                     setLocale(requireActivity(), languageCode);
@@ -426,7 +426,7 @@ private void onRecentLanguageClicked(String keyListPreference, Dialog dialog, Ad
         recentLanguagesDao.addRecentLanguage(
             new Language(recentLanguageName, recentLanguageCode));
         saveLanguageValue(recentLanguageCode, keyListPreference);
-        final Locale defLocale = new Locale(recentLanguageCode);
+        final Locale defLocale = createLocale(recentLanguageCode);
         if (keyListPreference.equals("appUiDefaultLanguagePref")) {
             appUiLanguageListPreference.setSummary(defLocale.getDisplayLanguage(defLocale));
             setLocale(requireActivity(), recentLanguageCode);
@@ -455,7 +455,7 @@ public void setLocale(final Activity activity, String userSelectedValue) {
         if (userSelectedValue.equals("")) {
             userSelectedValue = Locale.getDefault().getLanguage();
         }
-        final Locale locale = new Locale(userSelectedValue);
+        final Locale locale = createLocale(userSelectedValue);
         Locale.setDefault(locale);
         final Configuration configuration = new Configuration();
         configuration.locale = locale;
@@ -467,6 +467,25 @@ public void setLocale(final Activity activity, String userSelectedValue) {
         editor.apply();
     }
 
+    /**
+     * Create Locale based on different types of language codes
+     * @param languageCode
+     * @return Locale and throws error for invalid language codes
+     */
+    public static Locale createLocale(String languageCode) {
+        String[] parts = languageCode.split("-");
+        switch (parts.length) {
+            case 1:
+                return new Locale(parts[0]);
+            case 2:
+                return new Locale(parts[0], parts[1]);
+            case 3:
+                return new Locale(parts[0], parts[1], parts[2]);
+            default:
+                throw new IllegalArgumentException("Invalid language code: " + languageCode);
+        }
+    }
+
     /**
      * Save userselected language in List Preference
      * @param userSelectedValue

app/src/test/kotlin/fr/free/nrw/commons/settings/SettingsFragmentUnitTests.kt

@@ -19,8 +19,10 @@ import fr.free.nrw.commons.TestCommonsApplication
 import fr.free.nrw.commons.recentlanguages.Language
 import fr.free.nrw.commons.recentlanguages.RecentLanguagesAdapter
 import fr.free.nrw.commons.recentlanguages.RecentLanguagesDao
-import fr.free.nrw.commons.upload.UploadMediaDetailAdapter
+import fr.free.nrw.commons.settings.SettingsFragment.createLocale
 import org.junit.Assert
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -34,6 +36,8 @@ import org.robolectric.Shadows
 import org.robolectric.annotation.Config
 import org.robolectric.annotation.LooperMode
 import java.lang.reflect.Method
+import java.util.Locale
+
 
 @RunWith(RobolectricTestRunner::class)
 @Config(sdk = [21], application = TestCommonsApplication::class)
@@ -255,4 +259,30 @@ class SettingsFragmentUnitTests {
         verify(recentLanguagesTextView, times(1)).visibility = View.VISIBLE
     }
 
+    @Test
+    fun testCreateLocaleWithLanguageCode() {
+        val locale: Locale = createLocale("en")
+
+        assertEquals("en", locale.language)
+        assertEquals("",locale.country)
+        assertEquals("",locale.variant)
+    }
+
+    @Test
+    fun testCreateLocaleWithLanguageAndCountryCode() {
+        val locale: Locale = createLocale("zh-CN")
+
+        assertEquals("zh", locale.language)
+        assertEquals("CN",locale.country)
+        assertEquals("",locale.variant)
+    }
+
+    @Test
+    fun testCreateLocaleWithLanguageCountryAndVariantCode() {
+        val locale: Locale = createLocale("pt-BR-variant")
+
+        assertEquals("pt", locale.language)
+        assertEquals("BR",locale.country)
+        assertEquals("variant",locale.variant)
+    }
 }