set first theme choice as default

workaround for not knowing how to set default based on os version:
don't set default, and when there's none set use the first in the
list.

xwords4/android/app/src/main/java/org/eehouse/android/xw4/PrefsDelegate.java

@@ -159,10 +159,18 @@ public class PrefsDelegate extends DelegateBase
     protected void onResume()
     {
         super.onResume();
-        getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
+        SharedPreferences sp = getSharedPreferences();
+        sp.registerOnSharedPreferenceChangeListener( this );
 
         // It's too early somehow to do this in init() above
         findViewById( R.id.prefs_menu ).setOnClickListener(this);
+
+        String key = LocUtils.getString( mActivity, R.string.key_theme_which );
+        if ( null == sp.getString( key, null ) ) {
+            Resources res = mActivity.getResources();
+            String[] vals = res.getStringArray( R.array.color_themes );
+            sp.edit().putString( key, vals[0] ).commit();
+        }
     }
 
     @Override

xwords4/android/app/src/main/res/.gitignore

@@ -1,2 +1,2 @@
-values-*/strings.xml
+values-*/
 **/*__gen.png

xwords4/android/app/src/main/res/values-v29/common_rsrc.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:tools="http://schemas.android.com/tools"
+           tools:ignore="MissingTranslation"
+           >
+  <string-array name="color_themes">
+    <item>@string/color_use_theme_os</item>
+    <item>@string/color_use_theme_light</item>
+    <item>@string/color_use_theme_dark</item>
+  </string-array>
+
+</resources>

xwords4/android/app/src/main/res/values-v29/strings.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:tools="http://schemas.android.com/tools"
+           tools:ignore="MissingTranslation"
+           >
+  <string name="color_use_theme_os">Use Theme from Android Settings</string>
+</resources>

xwords4/android/app/src/main/res/values/common_rsrc.xml

@@ -386,7 +386,6 @@
   <string-array name="color_themes">
     <item>@string/color_use_theme_light</item>
     <item>@string/color_use_theme_dark</item>
-    <item>@string/color_use_theme_os</item>
   </string-array>
 
   <!-- Keep in sync with the color_ids_{light,dark} below -->

xwords4/android/app/src/main/res/values/strings.xml

@@ -2746,7 +2746,6 @@
     <string name="theme_which">Board color theme</string>
     <string name="color_use_theme_light">Use Light theme</string>
     <string name="color_use_theme_dark">Use Dark theme</string>
-    <string name="color_use_theme_os">Use Theme from Android Settings</string>
     <string name="color_theme_edit_light">Edit Light theme</string>
     <string name="color_theme_edit_dark">Edit Dark theme</string>
 

xwords4/android/app/src/main/res/xml/prefs_appear_themes.xml

@@ -6,12 +6,12 @@
   <PreferenceCategory android:title="@string/prefs_themes"
                       >
 
+    <!-- color_use_theme_os only defined for v29+... -->
     <org.eehouse.android.xw4.XWListPreference
         android:key="@string/key_theme_which"
         android:title="@string/theme_which"
         android:entries="@array/color_themes"
         android:entryValues="@array/color_themes"
-        android:defaultValue="@string/color_use_theme_os"
         />
 
     <Preference app:title="@string/color_theme_edit_light"