#1738 Android OS language changes are ignored - add device default case to respect device settings

app/src/main/AndroidManifest.xml

@@ -28,7 +28,7 @@
     <activity android:name=".intro.IntroActivity" />
     <activity
       android:name=".main.KiwixMainActivity"
-      android:configChanges="orientation|keyboardHidden|screenSize|locale"
+      android:configChanges="orientation|keyboardHidden|screenSize"
       android:label="@string/app_name"
       android:launchMode="singleTop"
       android:windowSoftInputMode="adjustPan">

core/src/main/java/org/kiwix/kiwixmobile/core/main/CoreMainActivity.java

@@ -1404,8 +1404,7 @@ public abstract class CoreMainActivity extends BaseActivity
         break;
       case REQUEST_PREFERENCES:
         if (resultCode == RESULT_RESTART) {
-          startActivity(Intents.internal(CoreMainActivity.class));
-          finish();
+          recreate();
         }
         if (resultCode == RESULT_HISTORY_CLEARED) {
           webViewList.clear();

core/src/main/java/org/kiwix/kiwixmobile/core/settings/CorePrefsFragment.java

@@ -44,6 +44,7 @@ import java.util.Locale;
 import javax.inject.Inject;
 import kotlin.Unit;
 import kotlin.io.FilesKt;
+import org.jetbrains.annotations.NotNull;
 import org.kiwix.kiwixmobile.core.CoreApp;
 import org.kiwix.kiwixmobile.core.NightModeConfig;
 import org.kiwix.kiwixmobile.core.R;
@@ -119,25 +120,20 @@ public abstract class CorePrefsFragment extends PreferenceFragment implements
 
   protected void setUpLanguageChooser(String preferenceId) {
     ListPreference languagePref = (ListPreference) findPreference(preferenceId);
-    String selectedLang = sharedPreferenceUtil.getPrefLanguage(Locale.getDefault().toString());
     List<String> languageCodeList = new LanguageUtils(getActivity()).getKeys();
-    selectedLang = languageCodeList.contains(selectedLang) ? selectedLang : "en";
-    String code[] = languageCodeList.toArray(new String[0]);
-    String[] entries = new String[code.length];
-    for (int index = 0; index < code.length; index++) {
-      Locale locale = new Locale(code[index]);
-      entries[index] =
-        locale.getDisplayLanguage() + " (" + locale.getDisplayLanguage(locale) + ") ";
-    }
-    languagePref.setEntries(entries);
-    languagePref.setEntryValues(code);
+    languageCodeList.add(0, Locale.ROOT.getLanguage());
+    final String selectedLang =
+      selectedLanguage(languageCodeList, sharedPreferenceUtil.getPrefLanguage());
+    languagePref.setEntries(languageDisplayValues(languageCodeList));
+    languagePref.setEntryValues(languageCodeList.toArray(new String[0]));
     languagePref.setDefaultValue(selectedLang);
     languagePref.setValue(selectedLang);
-    languagePref.setTitle(new Locale(selectedLang).getDisplayLanguage());
+    languagePref.setTitle(selectedLang.equals(Locale.ROOT.toString())
+      ? getString(R.string.device_default)
+      : new Locale(selectedLang).getDisplayLanguage());
     languagePref.setOnPreferenceChangeListener((preference, newValue) -> {
       String languageCode = (String) newValue;
       LanguageUtils.handleLocaleChange(getActivity(), languageCode);
-      preference.setTitle(new Locale(languageCode).getLanguage());
       sharedPreferenceUtil.putPrefLanguage(languageCode);
       restartActivity();
       return true;
@@ -150,6 +146,20 @@ public abstract class CorePrefsFragment extends PreferenceFragment implements
     getActivity().startActivity(new Intent(getActivity(), getActivity().getClass()));
   }
 
+  @NotNull private String selectedLanguage(List<String> languageCodeList, String langPref) {
+    return languageCodeList.contains(langPref) ? langPref : "en";
+  }
+
+  @NotNull private String[] languageDisplayValues(List<String> languageCodeList) {
+    String[] entries = new String[languageCodeList.size()];
+    entries[0] = getString(R.string.device_default);
+    for (int i = 1; i < languageCodeList.size(); i++) {
+      Locale locale = new Locale(languageCodeList.get(i));
+      entries[i] = locale.getDisplayLanguage() + " (" + locale.getDisplayLanguage(locale) + ") ";
+    }
+    return entries;
+  }
+
   private void setAppVersionNumber() {
     EditTextPreference versionPref = (EditTextPreference) findPreference(PREF_VERSION);
     versionPref.setSummary(getVersionName() + " Build: " + getVersionCode());

core/src/main/java/org/kiwix/kiwixmobile/core/utils/LanguageUtils.kt

@@ -30,6 +30,7 @@ import android.view.InflateException
 import android.view.LayoutInflater
 import android.view.View
 import android.widget.TextView
+import androidx.core.os.ConfigurationCompat
 import org.kiwix.kiwixmobile.core.extensions.locale
 import org.kiwix.kiwixmobile.core.utils.Constants.TAG_KIWIX
 import org.kiwix.kiwixmobile.core.utils.files.FileUtils
@@ -65,7 +66,7 @@ class LanguageUtils(private val context: Context) {
   }
 
   private fun haveToChangeFont(sharedPreferenceUtil: SharedPreferenceUtil): Boolean {
-    if (sharedPreferenceUtil.getPrefLanguage("").isEmpty()) {
+    if (sharedPreferenceUtil.prefLanguage == Locale.ROOT.toString()) {
       return false
     }
     return Locale.getAvailableLocales().firstOrNull { locale ->
@@ -183,16 +184,16 @@ class LanguageUtils(private val context: Context) {
       context: Context,
       sharedPreferenceUtil: SharedPreferenceUtil
     ) {
-      val language = sharedPreferenceUtil.getPrefLanguage("")
-      if (language.isEmpty()) {
-        return
+      sharedPreferenceUtil.prefLanguage.takeIf { it != Locale.ROOT.toString() }?.let {
+        handleLocaleChange(context, it)
       }
-      handleLocaleChange(context, language)
     }
 
     @JvmStatic
     fun handleLocaleChange(context: Context, language: String) {
-      val locale = Locale(language)
+      val locale =
+        if (language != Locale.ROOT.toString()) Locale(language)
+        else ConfigurationCompat.getLocales(context.applicationContext.resources.configuration)[0]
       Locale.setDefault(locale)
       val config = Configuration()
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {

core/src/main/java/org/kiwix/kiwixmobile/core/utils/SharedPreferenceUtil.java

@@ -28,6 +28,7 @@ import io.reactivex.Flowable;
 import io.reactivex.processors.PublishProcessor;
 import java.io.File;
 import java.util.HashSet;
+import java.util.Locale;
 import java.util.Set;
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -104,8 +105,8 @@ public class SharedPreferenceUtil {
     return sharedPreferences.getFloat(PREF_ZOOM, 100.0f);
   }
 
-  public String getPrefLanguage(String defaultLanguage) {
-    return sharedPreferences.getString(PREF_LANG, defaultLanguage);
+  public String getPrefLanguage() {
+    return sharedPreferences.getString(PREF_LANG, Locale.ROOT.toString());
   }
 
   public String getPrefStorage() {

core/src/main/res/values/strings.xml

@@ -295,6 +295,7 @@
   <string name="no_results">No Results</string>
   <string name="no_bookmarks">No Bookmarks</string>
   <string name="no_history">No History</string>
+  <string name="device_default">Device Default</string>
   <string-array name="pref_night_modes_entries">
     <item>On</item>
     <item>Off</item>