Notification on lockscreen settings: add WhatToShowController

Add WhatToShowController to handle the visibility change of the
preference category when the global setting changes.

Bug: 367455695
Flag: com.android.server.notification.notification_lock_screen_settings
Test: manual
Change-Id: I432e4c865402ac8bee32f0f79b3cf2bdce7cc882

src/com/android/settings/notification/LockScreenWhatToShowController.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.notification;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.database.ContentObserver;
+import android.net.Uri;
+import android.os.Handler;
+import android.os.Looper;
+import android.provider.Settings;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleEventObserver;
+import androidx.lifecycle.LifecycleOwner;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+
+import com.android.settings.widget.PreferenceCategoryController;
+
+public class LockScreenWhatToShowController extends PreferenceCategoryController implements
+        LifecycleEventObserver {
+
+    @Nullable
+    private Preference mPreference;
+    private final ContentResolver mContentResolver;
+
+    final ContentObserver mContentObserver = new ContentObserver(
+            new Handler(Looper.getMainLooper())) {
+        @Override
+        public void onChange(boolean selfChange, @Nullable Uri uri) {
+            if (mPreference == null) return;
+            updateState(mPreference);
+        }
+    };
+
+    @Override
+    public void updateState(@Nullable Preference preference) {
+        super.updateState(preference);
+        if (preference == null) return;
+        preference.setVisible(isAvailable());
+    }
+
+    public LockScreenWhatToShowController(@NonNull Context context, @NonNull String key) {
+        super(context, key);
+        mContentResolver = context.getContentResolver();
+    }
+
+    @Override
+    public void displayPreference(@NonNull PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mPreference = screen.findPreference(getPreferenceKey());
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        if (!lockScreenShowNotification()) {
+            return CONDITIONALLY_UNAVAILABLE;
+        }
+        return AVAILABLE;
+    }
+
+    /**
+     * @return Whether showing notifications on the lockscreen is enabled.
+     */
+    private boolean lockScreenShowNotification() {
+        return Settings.Secure.getInt(
+                mContext.getContentResolver(),
+                Settings.Secure.LOCK_SCREEN_SHOW_NOTIFICATIONS,
+                LockScreenNotificationsGlobalPreferenceController.OFF
+        ) == LockScreenNotificationsGlobalPreferenceController.ON;
+    }
+
+    @Override
+    public void onStateChanged(@NonNull LifecycleOwner lifecycleOwner,
+            @NonNull Lifecycle.Event event) {
+        if (event == Lifecycle.Event.ON_RESUME) {
+            mContentResolver.registerContentObserver(
+                    Settings.Secure.getUriFor(Settings.Secure.LOCK_SCREEN_SHOW_NOTIFICATIONS),
+                    /* notifyForDescendants= */ false, mContentObserver);
+        } else if (event == Lifecycle.Event.ON_PAUSE) {
+            mContentResolver.unregisterContentObserver(mContentObserver);
+        }
+    }
+}