Make use of opoc/LanguagePreference (fixes #169)

app/build.gradle

@@ -32,6 +32,7 @@ android {
 
         buildConfigField "boolean", "IS_TEST_BUILD", "false"
         buildConfigField "boolean", "IS_GPLAY_BUILD", "false"
+        buildConfigField("String[]", "APPLICATION_LANGUAGES", '{' + getUsedAndroidLanguages().collect {"\"${it}\""}.join(",")  + '}')
 
         vectorDrawables.useSupportLibrary = true
     }
@@ -92,6 +93,23 @@ dependencies {
     annotationProcessor "com.jakewharton:butterknife-compiler:${version_lib.butterknife}"
 }
 
+@SuppressWarnings(["UnnecessaryQualifiedReference", "SpellCheckingInspection"])
+static String[] getUsedAndroidLanguages() {
+    Set<String> langs = new HashSet<>()
+    new File('.').eachFileRecurse(groovy.io.FileType.DIRECTORIES) {
+        final foldername = it.name
+        if (foldername.startsWith('values-') && !it.canonicalPath.contains("build" + File.separator + "intermediates")) {
+            new File(it.toString()).eachFileRecurse(groovy.io.FileType.FILES) {
+                if (it.name.toLowerCase().endsWith(".xml") && it.getCanonicalFile().getText('UTF-8').contains("<string")) {
+                    langs.add(foldername.replace("values-", ""))
+
+                }
+            }
+        }
+    }
+    return langs.toArray(new String[langs.size()])
+}
+
 //  #####################
 //  Groovy Coding Area
 //  #####################

app/src/main/java/net/gsantner/opoc/ui/LanguagePreference.java

@@ -39,10 +39,8 @@ static String[] getUsedAndroidLanguages() {
  * Summary: Change language of this app. Restart app for changes to take effect
 
  * Define element in Preferences-XML:
-    <!--suppress AndroidDomInspection -->
     <net.gsantner.opoc.ui.LanguagePreference
         android:icon="@drawable/ic_language_black_24dp"
-        android:defaultValue=""
         android:key="@string/pref_key__language"
         android:summary="@string/pref_desc__language"
         android:title="@string/pref_title__language"/>
@@ -55,18 +53,25 @@ import android.os.Build;
 import android.preference.ListPreference;
 import android.util.AttributeSet;
 
+import net.gsantner.opoc.util.ContextUtils;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 
-import net.gsantner.opoc.util.ContextUtils;
-
 /**
  * A {@link android.preference.ListPreference} that displays a list of languages to select from
  */
-@SuppressWarnings({"unused", "SpellCheckingInspection"})
+@SuppressWarnings({"unused", "SpellCheckingInspection", "WeakerAccess"})
 public class LanguagePreference extends ListPreference {
+    private static final String SYSTEM_LANGUAGE_CODE = "";
+    public static String SYSTEM_LANGUAGE_NAME = "System";
+
+    // The language of res/values/ -> (usually English)
+    public static String DEFAULT_LANGUAGE_NAME = "English";
+    public static String DEFAULT_LANGUAGE_CODE = "en";
+
     public LanguagePreference(Context context) {
         super(context);
         init(context, null);
@@ -99,13 +104,15 @@ public class LanguagePreference extends ListPreference {
     }
 
     private void init(Context context, AttributeSet attrs) {
+        setDefaultValue(SYSTEM_LANGUAGE_CODE);
+
         // Fetch readable details
-        ContextUtils ContextUtils = new ContextUtils(context);
+        ContextUtils contextUtils = new ContextUtils(context);
         List<String> languages = new ArrayList<>();
-        Object bcof = ContextUtils.getBuildConfigValue("APPLICATION_LANGUAGES");
+        Object bcof = contextUtils.getBuildConfigValue("APPLICATION_LANGUAGES");
         if (bcof instanceof String[]) {
             for (String langId : (String[]) bcof) {
-                Locale locale = ContextUtils.getLocaleByAndroidCode(langId);
+                Locale locale = contextUtils.getLocaleByAndroidCode(langId);
                 languages.add(summarizeLocale(locale) + ";" + langId);
             }
         }
@@ -120,10 +127,10 @@ public class LanguagePreference extends ListPreference {
             entries[i + 2] = languages.get(i).split(";")[0];
             entryval[i + 2] = languages.get(i).split(";")[1];
         }
-        entries[0] = "System";
+        entries[0] = SYSTEM_LANGUAGE_NAME;
-        entryval[0] = "";
+        entryval[0] = SYSTEM_LANGUAGE_CODE;
-        entries[1] = "English";
+        entries[1] = DEFAULT_LANGUAGE_NAME;
-        entryval[1] = "en";
+        entryval[1] = DEFAULT_LANGUAGE_CODE;
 
         setEntries(entries);
         setEntryValues(entryval);

app/src/main/res/xml/preferences__master.xml

@@ -17,16 +17,12 @@
             android:summary="@string/pref_desc__sub_nav_slider"
             android:title="@string/pref_title__sub_nav_slider"/>
 
-        <ListPreference
+        <net.gsantner.opoc.ui.LanguagePreference
-            android:defaultValue=""
-            android:entries="@array/pref_arrdisp__language"
-            android:entryValues="@array/pref_arrkeys__language"
             android:icon="@drawable/ic_language_black_48px"
             android:key="@string/pref_key__language"
             android:summary="@string/pref_desc__language"
             android:title="@string/pref_title__language"/>
 
-
         <ListPreference
             android:dialogTitle="@string/pref_title__font_size"
             android:entries="@array/pref_entries__font_size"