Allows for system navigation settings to be added dynamically.

This allows for controller-backed preferences to be added or
overridden via xml.

Similarly, if the controllers cause all of the preferences for
2 or 3 button nav to be unavailable, we hide the settings button.

Bug: 324036308
Test: Manual and unit tests
Flag: NA
Change-Id: I2371f3173076172489966728ac69c8767570cd56

src/com/android/settings/core/PreferenceControllerListHelper.java

@@ -27,6 +27,8 @@ import android.text.TextUtils;
 import android.util.Log;
 
 import androidx.annotation.NonNull;
+import androidx.preference.PreferenceManager;
+import androidx.preference.PreferenceScreen;
 
 import com.android.settings.core.PreferenceXmlParserUtils.MetadataFlag;
 import com.android.settingslib.core.AbstractPreferenceController;
@@ -93,6 +95,25 @@ public class PreferenceControllerListHelper {
         return controllers;
     }
 
+    /**
+     * Checks if the given PreferenceScreen will be empty due to all preferences being unavailable.
+     *
+     * @param xmlResId resource id of the PreferenceScreen to check
+     * @return {@code true} if none of the preferences in the given screen will appear
+     */
+    public static boolean areAllPreferencesUnavailable(@NonNull Context context,
+            @NonNull PreferenceManager preferenceManager, @XmlRes int xmlResId) {
+        PreferenceScreen screen = preferenceManager.inflateFromResource(context, xmlResId,
+                /* rootPreferences= */ null);
+        List<BasePreferenceController> preferenceControllers =
+                getPreferenceControllersFromXml(context, xmlResId);
+        if (screen.getPreferenceCount() != preferenceControllers.size()) {
+            // There are some preferences without controllers, which will show regardless.
+            return false;
+        }
+        return preferenceControllers.stream().noneMatch(BasePreferenceController::isAvailable);
+    }
+
     /**
      * Return a sub list of {@link AbstractPreferenceController} to only contain controller that
      * doesn't exist in filter.