UI: re-add OLED friendly (aka black) theme.

Fixes #1625.

src/main/java/de/dennisguse/opentracks/AbstractActivity.java

@@ -22,6 +22,7 @@ import android.view.View;
 import androidx.appcompat.app.AppCompatActivity;
 
 import de.dennisguse.opentracks.services.announcement.TTSManager;
+import de.dennisguse.opentracks.settings.PreferencesUtils;
 
 /**
  * @author Jimmy Shih
@@ -30,6 +31,10 @@ public abstract class AbstractActivity extends AppCompatActivity {
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
+        if (PreferencesUtils.shouldApplyOledTheme()) {
+            setTheme(R.style.OpenTracksThemeOled);
+        }
+
         super.onCreate(savedInstanceState);
 
         // Set volume control stream for text to speech

src/main/java/de/dennisguse/opentracks/settings/PreferencesUtils.java

@@ -87,6 +87,10 @@ public class PreferencesUtils {
         changeListener.onSharedPreferenceChanged(sharedPreferences, null);
     }
 
+    public static void registerOnSharedPreferenceChangeListenerSilent(SharedPreferences.OnSharedPreferenceChangeListener changeListener) {
+        sharedPreferences.registerOnSharedPreferenceChangeListener(changeListener);
+    }
+
     public static void unregisterOnSharedPreferenceChangeListener(SharedPreferences.OnSharedPreferenceChangeListener changeListener) {
         sharedPreferences.unregisterOnSharedPreferenceChangeListener(changeListener);
     }
@@ -670,13 +674,29 @@ public class PreferencesUtils {
     }
 
     /**
-     * @return {@link androidx.appcompat.app.AppCompatDelegate}.MODE_*
+     * @return * {@link androidx.appcompat.app.AppCompatDelegate}.MODE_*
+     * * 3: Night OLED friendly
      */
-    public static int getDefaultNightMode() {
+    private static String getUiMode() {
         final String defaultValue = getKey(R.string.night_mode_default);
         final String value = getString(R.string.night_mode_key, defaultValue);
 
-        return Integer.parseInt(value);
+        return value;
+    }
+
+    public static boolean shouldApplyOledTheme() {
+        return resources.getString(R.string.night_mode_night_oled_value)
+                .equals(getUiMode());
+    }
+
+    public static void applyNightMode() {
+        String uiMode = getUiMode();
+        if (resources.getString(R.string.night_mode_night_oled_value)
+                .equals(uiMode)) {
+            return;
+        }
+
+        AppCompatDelegate.setDefaultNightMode(Integer.parseInt(uiMode));
     }
 
     public static void resetPreferences(Context context, boolean readAgain) {
@@ -823,10 +843,6 @@ public class PreferencesUtils {
         }
     }
 
-    public static void applyNightMode() {
-        AppCompatDelegate.setDefaultNightMode(PreferencesUtils.getDefaultNightMode());
-    }
-
     //TODO Check if resetPreferences can be used instead.
     @Deprecated
     @VisibleForTesting

src/main/java/de/dennisguse/opentracks/settings/UserInterfaceSettingsFragment.java

@@ -4,6 +4,7 @@ import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Build;
 import android.os.Bundle;
+import android.widget.Toast;
 
 import androidx.fragment.app.DialogFragment;
 import androidx.preference.ListPreference;
@@ -20,7 +21,10 @@ public class UserInterfaceSettingsFragment extends PreferenceFragmentCompat {
 
     private final SharedPreferences.OnSharedPreferenceChangeListener sharedPreferenceChangeListener = (sharedPreferences, key) -> {
         if (PreferencesUtils.isKey(R.string.night_mode_key, key)) {
-            getActivity().runOnUiThread(PreferencesUtils::applyNightMode);
+            getActivity().runOnUiThread(() -> {
+                PreferencesUtils.applyNightMode();
+                Toast.makeText(getContext(), R.string.settings_theme_switch_restart, Toast.LENGTH_LONG).show();
+            });
         }
     };
 
@@ -50,7 +54,7 @@ public class UserInterfaceSettingsFragment extends PreferenceFragmentCompat {
     @Override
     public void onResume() {
         super.onResume();
-        PreferencesUtils.registerOnSharedPreferenceChangeListener(sharedPreferenceChangeListener);
+        PreferencesUtils.registerOnSharedPreferenceChangeListenerSilent(sharedPreferenceChangeListener);
     }
 
     @Override