Disabling night theme selection if auto theme is not used

app/src/main/java/org/schabi/newpipe/settings/AppearanceSettingsFragment.java

@@ -44,7 +44,12 @@ public class AppearanceSettingsFragment extends BasePreferenceFragment {
                 return false;
             });
         } else {
-            removePreference(nightThemeKey);
+            // disable the night theme selection
+            final Preference preference = findPreference(nightThemeKey);
+            if (preference != null) {
+                preference.setEnabled(false);
+                preference.setSummary(getString(R.string.night_theme_available));
+            }
         }
     }
 
@@ -61,13 +66,6 @@ public class AppearanceSettingsFragment extends BasePreferenceFragment {
         return super.onPreferenceTreeClick(preference);
     }
 
-    private void removePreference(final String preferenceKey) {
-        final Preference preference = findPreference(preferenceKey);
-        if (preference != null) {
-            getPreferenceScreen().removePreference(preference);
-        }
-    }
-
     private void applyThemeChange(final String beginningThemeKey,
                                   final String themeKey,
                                   final Object newValue) {

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

@@ -714,6 +714,7 @@
     <string name="auto_device_theme_title">Automatic (device theme)</string>
     <string name="night_theme_summary">Select your favorite night theme — %s</string>
     <string name="select_night_theme_toast">You can select your favorite night theme below</string>
+    <string name="night_theme_available">This option is only available if Automatic (Device Theme) is selected for Theme</string>
     <string name="download_has_started">Download has started</string>
     <string name="description_select_note">You can now select text inside the description. Note that the page may flicker and links may not be clickable while in selection mode.</string>
     <string name="description_select_enable">Enable selecting text in the description</string>