allow to switch languages at runtime

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/GBActivity.java

@@ -1,14 +1,33 @@
 package nodomain.freeyourgadget.gadgetbridge.activities;
 
 
+import android.content.res.Configuration;
 import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
 
+import java.util.Locale;
+
 import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.R;
+import nodomain.freeyourgadget.gadgetbridge.util.Prefs;
 
 
 public class GBActivity extends AppCompatActivity {
+    private void setLanguage(String language) {
+        Locale locale;
+        if (language.equals("default")) {
+            locale = Locale.getDefault();
+        } else {
+            locale = new Locale(language);
+        }
+        Configuration config = new Configuration();
+        config.locale = locale;
+
+        // FIXME: I have no idea what I am doing
+        getApplicationContext().getResources().updateConfiguration(config, getApplicationContext().getResources().getDisplayMetrics());
+        getBaseContext().getResources().updateConfiguration(config, getBaseContext().getResources().getDisplayMetrics());
+    }
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         if (GBApplication.isDarkThemeEnabled()) {
@@ -17,6 +36,9 @@ public class GBActivity extends AppCompatActivity {
             setTheme(R.style.GadgetbridgeTheme);
         }
 
+        Prefs prefs = GBApplication.getPrefs();
+        String language = prefs.getString("language", "default");
+        setLanguage(language);
         super.onCreate(savedInstanceState);
     }
 }

app/src/main/res/values/arrays.xml

@@ -11,6 +11,36 @@
     <string name="pref_theme_value_light" translatable="false">light</string>
     <string name="pref_theme_value_dark" translatable="false">dark</string>
 
+    <string-array name="pref_language_options">
+        <item name="default">System Default</item>
+        <item name="de">Deutsch</item>
+        <item name="en">English</item>
+        <item name="es">Español</item>
+        <item name="fr">Français</item>
+        <item name="pl">Polski</item>
+        <item name="ru">Русский</item>
+        <item name="vi">Tiếng Việt</item>
+        <item name="tr">Türkçe</item>
+        <item name="uk">Українська</item>
+        <item name="ko">한국어</item>
+        <item name="ja">日本語</item>
+    </string-array>
+
+    <string-array name="pref_language_values">
+        <item>default</item>
+        <item>de</item>
+        <item>en</item>
+        <item>es</item>
+        <item>fr</item>
+        <item>pl</item>
+        <item>ru</item>
+        <item>vi</item>
+        <item>tr</item>
+        <item>uk</item>
+        <item>ko</item>
+        <item>ja</item>
+    </string-array>
+
     <string-array name="notification_mode">
         <item>@string/always</item>
         <item>@string/when_screen_off</item>

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

@@ -47,6 +47,8 @@
     <string name="pref_theme_light">Light</string>
     <string name="pref_theme_dark">Dark</string>
 
+    <string name="pref_title_language">Language</string>
+
     <string name="pref_header_notifications">Notifications</string>
     <string name="pref_title_notifications_repetitions">Repetitions</string>
     <string name="pref_title_notifications_call">Phone Calls</string>

app/src/main/res/xml/preferences.xml

@@ -23,6 +23,13 @@
             android:entryValues="@array/pref_theme_values"
             android:defaultValue="@string/pref_theme_value_light"
             android:summary="%s" />
+        <ListPreference
+            android:key="language"
+            android:title="@string/pref_title_language"
+            android:entries="@array/pref_language_options"
+            android:entryValues="@array/pref_language_values"
+            android:defaultValue="default"
+            android:summary="%s" />
     </PreferenceCategory>
     <PreferenceCategory
         android:key="pref_key_datetime"