totally overhaul choosing locales from app metadata based on LocaleList

This makes the selection logic heed the list of preferred locales from the
user Settings.

closes #987
closes #1186
refs #1440 #1882 #1730
!886

app/src/main/java/org/fdroid/fdroid/FDroidApp.java

@@ -67,6 +67,7 @@ import org.apache.commons.net.util.SubnetUtils;
 import org.fdroid.fdroid.Preferences.ChangeListener;
 import org.fdroid.fdroid.Preferences.Theme;
 import org.fdroid.fdroid.compat.PRNGFixes;
+import org.fdroid.fdroid.data.App;
 import org.fdroid.fdroid.data.AppProvider;
 import org.fdroid.fdroid.data.InstalledAppProviderService;
 import org.fdroid.fdroid.data.Repo;
@@ -330,6 +331,7 @@ public class FDroidApp extends Application {
     public void onConfigurationChanged(Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
         Languages.setLanguage(this);
+        App.systemLocaleList = null;
 
         // update the descriptions based on the new language preferences
         SharedPreferences atStartTime = getAtStartTimeSharedPreferences();

app/src/main/java/org/fdroid/fdroid/data/App.java

@@ -10,7 +10,6 @@ import android.content.res.AssetManager;
 import android.content.res.Resources;
 import android.content.res.XmlResourceParser;
 import android.database.Cursor;
-import android.os.Build;
 import android.os.Environment;
 import android.os.LocaleList;
 import android.os.Parcel;
@@ -19,6 +18,8 @@ import android.text.TextUtils;
 import android.util.Log;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.os.ConfigurationCompat;
+import androidx.core.os.LocaleListCompat;
 import com.fasterxml.jackson.annotation.JacksonInject;
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -41,8 +42,8 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.Date;
 import java.util.Enumeration;
+import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -75,6 +76,14 @@ public class App extends ValueObject implements Comparable<App>, Parcelable {
     @JsonIgnore
     private static final String TAG = "App";
 
+    /**
+     * {@link LocaleListCompat} for finding the right app description material.
+     * It is set globally static to a) cache this value, since there are thousands
+     * of {@link App} entries, and b) make it easy to test {@link #setLocalized(Map)} )}
+     */
+    @JsonIgnore
+    public static LocaleListCompat systemLocaleList;
+
     // these properties are not from the index metadata, but represent the state on the device
     /**
      * True if compatible with the device (i.e. if at least one apk is)
@@ -98,8 +107,12 @@ public class App extends ValueObject implements Comparable<App>, Parcelable {
     public String preferredSigner;
     @JsonIgnore
     public boolean isApk;
+
+    /**
+     * Has this {@code App} been localized into one of the user's current locales.
+     */
     @JsonIgnore
-    boolean isLocalized = false;
+    boolean isLocalized;
 
     /**
      * This is primarily for the purpose of saving app metadata when parsing an index.xml file.
@@ -484,110 +497,25 @@ public class App extends ValueObject implements Comparable<App>, Parcelable {
      * {@code localized} block is included in the index.  Also, null strings in
      * the {@code localized} block should not overwrite Name/Summary/Description
      * strings with empty/null if they were set directly by Jackson.
-     * <p>
+     * <ol>
-     * Choosing the locale to use follows two sets of rules, one for Android versions
-     * older than {@code android-24} and the other for {@code android-24} or newer.
-     * The system-wide language preference list was added in {@code android-24}.
-     * <ul>
-     * <li>{@code >= android-24}<ol>
      * <li>the country variant {@code de-AT} from the user locale list
      * <li>only the language {@code de} from the above locale
+     * <li>next locale in the user's preference list ({@code >= android-24})
      * <li>{@code en-US} since its the most common English for software
      * <li>the first available {@code en} locale
-     * </ol></li>
+     * </ol>
-     * <li>{@code < android-24}<ol>
-     * <li>the country variant from the user locale: {@code de-AT}
-     * <li>only the language from the above locale:  {@code de}
-     * <li>all available locales with the same language:  {@code de-BE}
-     * <li>{@code en-US} since its the most common English for software
-     * <li>all available {@code en} locales
-     * </ol></li>
-     * </ul>
-     * On {@code >= android-24}, it is by design that this does not fallback to other
-     * country-specific locales, e.g. {@code fr-CH} does not fall back on {@code fr-FR}.
-     * If someone wants to fallback to {@code fr-FR}, they can add it to the system
-     * language list.  There are many cases where it is inappropriate to fallback to a
-     * different country-specific locale, for example {@code de-DE --> de-CH} or
-     * {@code zh-CN --> zh-TW}.
      * <p>
-     * On {@code < android-24}, the user can only set a single
+     * The system-wide language preference list was added in {@code android-24}.
-     * locale with a country as an option, so here it makes sense to try to fallback
+     *
-     * on other country-specific locales, rather than English.
+     * @see <a href="https://developer.android.com/guide/topics/resources/multilingual-support">Android language and locale resolution overview</a>
      */
     @JsonProperty("localized")
     void setLocalized(Map<String, Map<String, Object>> localized) { // NOPMD
-        Locale defaultLocale = Locale.getDefault();
+        if (systemLocaleList == null) {
-        String languageTag = defaultLocale.getLanguage();
+            systemLocaleList = ConfigurationCompat.getLocales(Resources.getSystem().getConfiguration());
-        String countryTag = defaultLocale.getCountry();
-        String localeTag;
-        if (TextUtils.isEmpty(countryTag)) {
-            localeTag = languageTag;
-        } else {
-            localeTag = languageTag + "-" + countryTag;
         }
-
+        Set<String> localesToUse = localized.keySet();
-        Set<String> availableLocales = localized.keySet();
+        setIsLocalized(localesToUse);
-        Set<String> localesToUse = new LinkedHashSet<>();
-        if (availableLocales.contains(localeTag)) {
-            localesToUse.add(localeTag);
-        }
-        if (availableLocales.contains(languageTag)) {
-            localesToUse.add(languageTag);
-        }
-        if (localesToUse.isEmpty()) {
-            // In case of non-standard region like [en-SE]
-            for (String availableLocale : availableLocales) {
-                String availableLanguage = availableLocale.split("-")[0];
-                if (languageTag.equals(availableLanguage)) {
-                    localesToUse.add(availableLocale);
-                }
-            }
-        }
-        if (Build.VERSION.SDK_INT >= 24) {
-            LocaleList localeList = Resources.getSystem().getConfiguration().getLocales();
-            String[] sortedLocaleList = localeList.toLanguageTags().split(",");
-            Arrays.sort(sortedLocaleList, new java.util.Comparator<String>() {
-                @Override
-                public int compare(String s1, String s2) {
-                    return s1.length() - s2.length();
-                }
-            });
-            for (String toUse : sortedLocaleList) {
-                localesToUse.add(toUse);
-                for (String l : availableLocales) {
-                    if (l.equals(toUse.split("-")[0])) {
-                        localesToUse.add(l);
-                        break;
-                    }
-                }
-            }
-        } else {
-            for (String l : availableLocales) {
-                if (l.startsWith(languageTag)) {
-                    localesToUse.add(l);
-                }
-            }
-        }
-        if (availableLocales.contains("en-US")) {
-            localesToUse.add("en-US");
-        }
-        for (String l : availableLocales) {
-            if (l.startsWith("en")) {
-                localesToUse.add(l);
-                break;
-            }
-        }
-
-        for (String l : localesToUse) {
-            if (l.startsWith(languageTag)) {
-                isLocalized = true;
-                break;
-            }
-        }
-        if (localesToUse.size() > 1) {
-            isLocalized = true;
-        }
-
         String value = getLocalizedEntry(localized, localesToUse, "whatsNew");
         if (!TextUtils.isEmpty(value)) {
             whatsNew = value;
@@ -625,58 +553,58 @@ public class App extends ValueObject implements Comparable<App>, Parcelable {
     }
 
     /**
-     * Returns the right localized version of this entry, based on an immitation of
+     * Sets the boolean flag {@link #isLocalized} if this app entry has an localized
-     * the logic that Android/Java uses.  On Android >= 24, this can get the
+     * entry in one of the user's current locales.
-     * "Language Priority List", but it doesn't always seem to be properly sorted.
+     *
-     * So this method has to kind of fake it by using {@link Locale#getDefault()}
+     * @see org.fdroid.fdroid.views.main.WhatsNewViewBinder#onCreateLoader(int, android.os.Bundle)
-     * as the first entry, then sorting the rest based on length (e.g. {@code de-AT}
+     */
-     * before {@code de}).
+    private void setIsLocalized(Set<String> supportedLocales) {
+        isLocalized = false;
+        for (int i = 0; i < systemLocaleList.size(); i++) {
+            String language = systemLocaleList.get(i).getLanguage();
+            for (String supportedLocale : supportedLocales) {
+                if (language.equals(supportedLocale.split("-")[0])) {
+                    isLocalized = true;
+                    return;
+                }
+            }
+        }
+    }
+
+    /**
+     * Returns the right localized version of this entry, based on an imitation of
+     * the logic that Android uses.
      *
      * @see LocaleList
-     * @see Locale#getDefault()
-     * @see java.util.Locale.LanguageRange
      */
     private String getLocalizedEntry(Map<String, Map<String, Object>> localized,
-                                     Set<String> locales, String key) {
+                                     Set<String> locales, @NonNull String key) {
-        try {
+        Map<String, Object> localizedLocaleMap = getLocalizedLocaleMap(localized, locales, key);
-            for (String locale : locales) {
+        if (localizedLocaleMap != null && !localizedLocaleMap.isEmpty()) {
-                if (localized.containsKey(locale)) {
+            for (Object entry : localizedLocaleMap.values()) {
-                    String value = (String) localized.get(locale).get(key);
+                return (String) entry; // NOPMD
-                    if (value != null) {
-                        return value;
             }
         }
-            }
-        } catch (ClassCastException e) {
-            Utils.debugLog(TAG, e.getMessage());
-        }
         return null;
     }
 
     private String getLocalizedGraphicsEntry(Map<String, Map<String, Object>> localized,
                                              Set<String> locales, String key) {
-        try {
+        Map<String, Object> localizedLocaleMap = getLocalizedLocaleMap(localized, locales, key);
-            for (String locale : locales) {
+        if (localizedLocaleMap != null && !localizedLocaleMap.isEmpty()) {
-                Map<String, Object> entry = localized.get(locale);
+            for (String locale : localizedLocaleMap.keySet()) {
-                if (entry != null) {
+                return locale + "/" + localizedLocaleMap.get(locale); // NOPMD
-                    Object value = entry.get(key);
-                    if (value != null && value.toString().length() > 0) {
-                        return locale + "/" + value;
             }
         }
-            }
-        } catch (ClassCastException e) {
-            Utils.debugLog(TAG, e.getMessage());
-        }
         return null;
     }
 
     private String[] getLocalizedListEntry(Map<String, Map<String, Object>> localized,
                                            Set<String> locales, String key) {
-        try {
+        Map<String, Object> localizedLocaleMap = getLocalizedLocaleMap(localized, locales, key);
-            for (String locale : locales) {
+        if (localizedLocaleMap != null && !localizedLocaleMap.isEmpty()) {
-                if (localized.containsKey(locale)) {
+            for (String locale : localizedLocaleMap.keySet()) {
-                    ArrayList<String> entry = (ArrayList<String>) localized.get(locale).get(key);
+                ArrayList<String> entry = (ArrayList<String>) localizedLocaleMap.get(locale);
                 if (entry != null && entry.size() > 0) {
                     String[] result = new String[entry.size()];
                     int i = 0;
@@ -688,12 +616,87 @@ public class App extends ValueObject implements Comparable<App>, Parcelable {
                 }
             }
         }
-        } catch (ClassCastException e) {
-            Utils.debugLog(TAG, e.getMessage());
-        }
         return new String[0];
     }
 
+    /**
+     * Return one matching entry from the {@code localized} block in the app entry
+     * in the index JSON.
+     */
+    private Map<String, Object> getLocalizedLocaleMap(Map<String, Map<String, Object>> localized,
+                                                      Set<String> locales, String key) {
+        String[] localesToUse = getLocalesForKey(localized, locales, key);
+        if (localesToUse.length > 0) {
+            Locale firstMatch = systemLocaleList.getFirstMatch(localesToUse);
+            if (firstMatch != null) {
+                for (String languageTag : new String[]{firstMatch.toLanguageTag(), null}) {
+                    if (languageTag == null) {
+                        languageTag = getFallbackLanguageTag(firstMatch, localesToUse); // NOPMD
+                    }
+                    Map<String, Object> localeEntry = localized.get(languageTag);
+                    if (localeEntry != null && localeEntry.containsKey(key)) {
+                        Object value = localeEntry.get(key);
+                        if (value != null) {
+                            Map<String, Object> localizedLocaleMap = new HashMap<>();
+                            localizedLocaleMap.put(languageTag, value);
+                            return localizedLocaleMap;
+                        }
+                    }
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Get all locales that have an entry for {@code key}.
+     */
+    private String[] getLocalesForKey(Map<String, Map<String, Object>> localized,
+                                      Set<String> locales, String key) {
+        Set<String> localesToUse = new HashSet<>();
+        for (String locale : locales) {
+            Map<String, Object> localeEntry = localized.get(locale);
+            if (localeEntry != null && localeEntry.get(key) != null) {
+                localesToUse.add(locale);
+            }
+        }
+        return localesToUse.toArray(new String[0]);
+    }
+
+    /**
+     * Look for the first language-country match for languages with multiple scripts.
+     * Then look for a language-only match, for when there is no exact
+     * {@link Locale} match.  Then try a locale with the same language, but
+     * different country. If there are still no matches, return the {@code en-US}
+     * entry. If all else fails, try to return the first existing English locale.
+     */
+    private String getFallbackLanguageTag(Locale firstMatch, String[] localesToUse) {
+        final String firstMatchLanguageCountry = firstMatch.getLanguage() + "-" + firstMatch.getCountry();
+        for (String languageTag : localesToUse) {
+            if (languageTag.equals(firstMatchLanguageCountry)) {
+                return languageTag;
+            }
+        }
+        final String firstMatchLanguage = firstMatch.getLanguage();
+        String englishLastResort = null;
+        for (String languageTag : localesToUse) {
+            if (languageTag.equals(firstMatchLanguage)) {
+                return languageTag;
+            } else if ("en-US".equals(languageTag)) {
+                englishLastResort = languageTag;
+            }
+        }
+        for (String languageTag : localesToUse) {
+            String languageToUse = languageTag.split("-")[0];
+            if (firstMatchLanguage.equals(languageToUse)) {
+                return languageTag;
+            } else if (englishLastResort == null && "en".equals(languageToUse)) {
+                englishLastResort = languageTag;
+            }
+        }
+        return englishLastResort;
+    }
+
     /**
      * Returns the app description text with all newlines replaced by {@code <br>}
      */

app/src/main/java/org/fdroid/fdroid/data/Schema.java

@@ -209,6 +209,13 @@ public interface Schema {
             String TV_SCREENSHOTS = "tvScreenshots";
             String WEAR_SCREENSHOTS = "wearScreenshots";
             String IS_APK = "isApk";
+
+            /**
+             * Has this {@code App} been localized into one of the user's current locales.
+             *
+             * @see App#setIsLocalized(java.util.Set)
+             * @see org.fdroid.fdroid.views.main.WhatsNewViewBinder#onCreateLoader(int, android.os.Bundle)
+             */
             String IS_LOCALIZED = "isLocalized";
 
             interface AutoInstallApk {

app/src/test/java/org/fdroid/fdroid/data/AppProviderTest.java

@@ -6,6 +6,7 @@ import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.net.Uri;
+import androidx.core.os.LocaleListCompat;
 import org.fdroid.fdroid.Preferences;
 import org.fdroid.fdroid.TestUtils;
 import org.fdroid.fdroid.data.Schema.AppMetadataTable.Cols;
@@ -303,7 +304,7 @@ public class AppProviderTest extends FDroidProviderTest {
         localized.put("es", es);
         localized.put("fr", fr);
 
-        Locale.setDefault(new Locale("nl", "NL"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("nl-NL");
         app.setLocalized(localized);
         assertFalse(app.isLocalized);
 
@@ -324,7 +325,7 @@ public class AppProviderTest extends FDroidProviderTest {
         app.setLocalized(localized);
         assertFalse(app.isLocalized);
 
-        Locale.setDefault(new Locale("en", "US"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-US");
         app = new App();
         localized.clear();
         localized.put("en-US", en);

app/src/test/java/org/fdroid/fdroid/data/LocaleSelectionTest.java

@@ -1,23 +1,27 @@
 package org.fdroid.fdroid.data;
 
-import android.content.res.Configuration;
 import android.os.Build;
-import android.os.LocaleList;
+import androidx.core.os.LocaleListCompat;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.commons.io.FileUtils;
 import org.fdroid.fdroid.TestUtils;
+import org.junit.Assume;
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.shadows.ShadowLog;
 
+import java.io.File;
+import java.io.IOException;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
-import static org.mockito.Mockito.when;
 
 @RunWith(RobolectricTestRunner.class)
 @SuppressWarnings("LocalVariableName")
@@ -25,83 +29,25 @@ public class LocaleSelectionTest {
 
     private static final String KEY = "summary";
 
-    @Test
+    private static final String EN_US_NAME = "Checkey: info on local apps\n";
-    public void correctLocaleSelectionBeforeSDK24() throws Exception {
+    private static final String EN_US_FEATURE_GRAPHIC = "en-US/featureGraphic.png";
-        TestUtils.setFinalStatic(Build.VERSION.class.getDeclaredField("SDK_INT"), 19);
+    private static final String EN_US_PHONE_SCREENSHOT = "en-US/phoneScreenshots/First.png";
-        assertTrue(Build.VERSION.SDK_INT < 24);
+    private static final String EN_US_SEVEN_INCH_SCREENSHOT = "en-US/sevenInchScreenshots/checkey-tablet.png";
-        App app;
+    private static final String FR_FR_NAME = "Checkey : infos applis locales";
+    private static final String FR_CA_FEATURE_GRAPHIC = "fr-CA/featureGraphic.png";
+    private static final String FR_FR_FEATURE_GRAPHIC = "fr-FR/featureGraphic.png";
+    private static final String FR_FR_SEVEN_INCH_SCREENSHOT = "fr-FR/sevenInchScreenshots/checkey-tablet.png";
 
-        Map<String, Map<String, Object>> localized = new HashMap<>();
+    @Before
-        HashMap<String, Object> en_US = new HashMap<>();
+    public final void setUp() {
-        en_US.put(KEY, "summary-en_US");
+        ShadowLog.stream = System.out;
-        HashMap<String, Object> de_AT = new HashMap<>();
-        de_AT.put(KEY, "summary-de_AT");
-        HashMap<String, Object> de_DE = new HashMap<>();
-        de_DE.put(KEY, "summary-de_DE");
-        HashMap<String, Object> sv = new HashMap<>();
-        sv.put(KEY, "summary-sv");
-        HashMap<String, Object> sv_FI = new HashMap<>();
-        sv_FI.put(KEY, "summary-sv_FI");
-
-        localized.put("de-AT", de_AT);
-        localized.put("de-DE", de_DE);
-        localized.put("en-US", en_US);
-        localized.put("sv", sv);
-        localized.put("sv-FI", sv_FI);
-
-        // Easy mode. en-US metadata with an en-US locale
-        Locale.setDefault(new Locale("en", "US"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(en_US.get(KEY), app.summary);
-
-        // Fall back to en-US locale, when we have a different en locale
-        Locale.setDefault(new Locale("en", "UK"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(en_US.get(KEY), app.summary);
-
-        // Fall back to language only
-        Locale.setDefault(new Locale("en", "UK"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(en_US.get(KEY), app.summary);
-
-        // select the correct one out of multiple language locales
-        Locale.setDefault(new Locale("de", "DE"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(de_DE.get(KEY), app.summary);
-
-        // Even when we have a non-exact matching locale, we should fall back to the same language
-        Locale.setDefault(new Locale("de", "CH"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(de_AT.get(KEY), app.summary);
-
-        // Test fallback to base lang with not exact matching locale
-        Locale.setDefault(new Locale("sv", "SE"));
-        app = new App();
-        app.setLocalized(localized);
-        assertEquals(sv.get(KEY), app.summary);
     }
 
     @Test
-    public void correctLocaleSelectionFromSDK24() throws Exception {
+    public void localeSelection() throws Exception {
 
-        TestUtils.setFinalStatic(Build.VERSION.class.getDeclaredField("SDK_INT"), 29);
+        App app = new App();
-        assertTrue(Build.VERSION.SDK_INT >= 24);
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-US,de-DE");
-
-        App app = spy(new App());
-
-        // we mock both the getLocales call and the conversion to a language tag string.
-        Configuration configuration = mock(Configuration.class);
-        LocaleList localeList = mock(LocaleList.class);
-        doReturn(localeList).when(configuration).getLocales();
-
-        // Set both default locale as well as the locale list, because the algorithm uses both...
-        Locale.setDefault(new Locale("en", "US"));
-        when(localeList.toLanguageTags()).thenReturn("en-US,de-DE");
 
         //no metadata present
         Map<String, Map<String, Object>> localized = new HashMap<>();
@@ -112,10 +58,18 @@ public class LocaleSelectionTest {
         en_US.put(KEY, "summary-en_US");
         HashMap<String, Object> en_GB = new HashMap<>();
         en_GB.put(KEY, "summary-en_GB");
+        HashMap<String, Object> de = new HashMap<>();
+        de.put(KEY, "summary-de");
         HashMap<String, Object> de_AT = new HashMap<>();
         de_AT.put(KEY, "summary-de_AT");
         HashMap<String, Object> de_DE = new HashMap<>();
         de_DE.put(KEY, "summary-de_DE");
+        HashMap<String, Object> es_ES = new HashMap<>();
+        es_ES.put(KEY, "summary-es_ES");
+        HashMap<String, Object> fr_FR = new HashMap<>();
+        fr_FR.put(KEY, "summary-fr_FR");
+        HashMap<String, Object> it_IT = new HashMap<>();
+        it_IT.put(KEY, "summary-it_IT");
 
         app.summary = "reset";
         localized.put("de-AT", de_AT);
@@ -125,8 +79,7 @@ public class LocaleSelectionTest {
         // just select the matching en-US locale, nothing special here
         assertEquals(en_US.get(KEY), app.summary);
 
-        Locale.setDefault(new Locale("en", "SE"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-SE,de-DE");
-        when(localeList.toLanguageTags()).thenReturn("en-SE,de-DE");
         app.setLocalized(localized);
         // Fall back to another en locale before de
         assertEquals(en_US.get(KEY), app.summary);
@@ -138,8 +91,7 @@ public class LocaleSelectionTest {
         localized.put("en-GB", en_GB);
         localized.put("en-US", en_US);
 
-        Locale.setDefault(new Locale("de", "AT"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("de-AT,de-DE");
-        when(localeList.toLanguageTags()).thenReturn("de-AT,de-DE");
         app.setLocalized(localized);
         // full match against a non-default locale
         assertEquals(de_AT.get(KEY), app.summary);
@@ -147,14 +99,13 @@ public class LocaleSelectionTest {
         app.summary = "reset";
         localized.clear();
         localized.put("de-AT", de_AT);
-        localized.put("de", de_DE);
+        localized.put("de", de);
         localized.put("en-GB", en_GB);
         localized.put("en-US", en_US);
 
-        Locale.setDefault(new Locale("de", "CH"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("de-CH,en-US");
-        when(localeList.toLanguageTags()).thenReturn("de-CH,en-US");
         app.setLocalized(localized);
-        assertEquals(de_DE.get(KEY), app.summary);
+        assertEquals(de.get(KEY), app.summary);
 
         app.summary = "reset";
         localized.clear();
@@ -162,13 +113,12 @@ public class LocaleSelectionTest {
         localized.put("en-US", en_US);
 
         Locale.setDefault(new Locale("en", "AU"));
-        when(localeList.toLanguageTags()).thenReturn("en-AU");
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-AU");
         app.setLocalized(localized);
         assertEquals(en_US.get(KEY), app.summary);
 
         app.summary = "reset";
-        Locale.setDefault(new Locale("zh", "TW", "#Hant"));
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("zh-Hant-TW,zh-Hans-CN");
-        when(localeList.toLanguageTags()).thenReturn("zh-Hant-TW,zh-Hans-CN");
         localized.clear();
         localized.put("en", en_GB);
         localized.put("en-US", en_US);
@@ -197,5 +147,107 @@ public class LocaleSelectionTest {
         localized.put("zh-CN", zh_CN);
         app.setLocalized(localized);
         assertEquals(zh_CN.get(KEY), app.summary);
+
+        localized.clear();
+        localized.put("en-US", en_US);
+        localized.put("zh-CN", zh_CN);
+        app.setLocalized(localized);
+        assertEquals(zh_CN.get(KEY), app.summary);
+
+        // https://developer.android.com/guide/topics/resources/multilingual-support#resource-resolution-examples
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("fr-CH");
+        localized.clear();
+        localized.put("en-US", en_US);
+        localized.put("de-DE", de_DE);
+        localized.put("es-ES", es_ES);
+        localized.put("fr-FR", fr_FR);
+        localized.put("it-IT", it_IT);
+        app.setLocalized(localized);
+        assertEquals(fr_FR.get(KEY), app.summary);
+
+        // https://developer.android.com/guide/topics/resources/multilingual-support#t-2d-choice
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("fr-CH,it-CH");
+        localized.clear();
+        localized.put("en-US", en_US);
+        localized.put("de-DE", de_DE);
+        localized.put("es-ES", es_ES);
+        localized.put("it-IT", it_IT);
+        app.setLocalized(localized);
+        assertEquals(it_IT.get(KEY), app.summary);
+    }
+
+    @Test
+    public void testSetLocalized() throws IOException {
+        Assume.assumeTrue(Build.VERSION.SDK_INT >= 24);
+
+        File f = TestUtils.copyResourceToTempFile("localized.json");
+        Map<String, Object> result = new ObjectMapper().readValue(
+                FileUtils.readFileToString(f, (String) null), HashMap.class);
+        List<Map<String, Object>> apps = (List<Map<String, Object>>) result.get("apps");
+        Map<String, Map<String, Object>> localized = (Map<String, Map<String, Object>>) apps.get(0).get("localized");
+        App app = new App();
+
+        App.systemLocaleList = LocaleListCompat.create(Locale.US);
+        app.setLocalized(localized);
+        assertEquals(EN_US_NAME, app.name);
+        assertEquals(EN_US_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(EN_US_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
+
+        // choose the language when there is an exact locale match
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("fr-FR");
+        app.setLocalized(localized);
+        assertEquals(FR_FR_NAME, app.name);
+        assertEquals(FR_FR_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(FR_FR_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
+
+        // choose the language from a different country when the preferred country is not available,
+        // while still choosing featureGraphic from exact match
+        App.systemLocaleList = LocaleListCompat.create(Locale.CANADA_FRENCH);
+        app.setLocalized(localized);
+        assertEquals(FR_FR_NAME, app.name);
+        assertEquals(FR_CA_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(FR_FR_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
+
+        // choose the third preferred language when first and second lack translations
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("bo-IN,sr-RS,fr-FR");
+        app.setLocalized(localized);
+        assertEquals(FR_FR_NAME, app.name);
+        assertEquals(FR_FR_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(FR_FR_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
+
+        // choose first language from different country, rather than 2nd full lang/country match
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-GB,fr-FR");
+        app.setLocalized(localized);
+        assertEquals(EN_US_NAME, app.name);
+        assertEquals(EN_US_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(EN_US_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
+
+        // choose en_US when no match, and mark as not localized
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("bo-IN,sr-RS");
+        app.setLocalized(localized);
+        assertEquals(EN_US_NAME, app.name);
+        assertEquals(EN_US_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(EN_US_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertFalse(app.isLocalized);
+
+        // When English is the preferred language and the second language has no entries
+        App.systemLocaleList = LocaleListCompat.forLanguageTags("en-US,sr-RS");
+        app.setLocalized(localized);
+        assertEquals(EN_US_NAME, app.name);
+        assertEquals(EN_US_FEATURE_GRAPHIC, app.featureGraphic);
+        assertEquals(EN_US_PHONE_SCREENSHOT, app.phoneScreenshots[0]);
+        assertEquals(EN_US_SEVEN_INCH_SCREENSHOT, app.sevenInchScreenshots[0]);
+        assertTrue(app.isLocalized);
     }
 }

app/src/test/java/org/fdroid/fdroid/updater/IndexV1UpdaterTest.java

@@ -370,6 +370,7 @@ public class IndexV1UpdaterTest extends FDroidProviderTest {
                 "isLocalized",
                 "preferredSigner",
                 "prefs",
+                "systemLocaleList",
                 "TAG",
         };
         runJsonIgnoreTest(new App(), allowedInApp, ignoredInApp);