[Catalyst] Lock screen summary is not updated

In original implementation, DashboardFragment.onResume calls
AbstractPreferenceController.updateState to refresh preference. While
after Catalyst migration, it requires explicit update when external
dependency is changed.

Bug: 397798327
Flag: com.android.settings.flags.catalyst_lockscreen_from_display_settings
Test: adb shell settings put secure lock_screen_show_notifications/lock_screen_allow_private_notifications
Change-Id: I1c16d7df62cdb1cb53d365f2636aa1dc0a424839

src/com/android/settings/security/LockScreenPreferenceScreen.kt

@@ -16,12 +16,19 @@
 package com.android.settings.security
 
 import android.content.Context
+import android.provider.Settings.Secure.LOCK_SCREEN_ALLOW_PRIVATE_NOTIFICATIONS
+import android.provider.Settings.Secure.LOCK_SCREEN_SHOW_NOTIFICATIONS
 import com.android.settings.R
 import com.android.settings.Settings.LockScreenSettingsActivity
 import com.android.settings.display.AmbientDisplayAlwaysOnPreference
 import com.android.settings.flags.Flags
 import com.android.settings.notification.LockScreenNotificationPreferenceController
 import com.android.settings.utils.makeLaunchIntent
+import com.android.settingslib.datastore.AbstractKeyedDataObservable
+import com.android.settingslib.datastore.HandlerExecutor
+import com.android.settingslib.datastore.KeyedObserver
+import com.android.settingslib.datastore.SettingsSecureStore
+import com.android.settingslib.metadata.PreferenceChangeReason
 import com.android.settingslib.metadata.PreferenceMetadata
 import com.android.settingslib.metadata.PreferenceSummaryProvider
 import com.android.settingslib.metadata.ProvidePreferenceScreen
@@ -29,7 +36,12 @@ import com.android.settingslib.metadata.preferenceHierarchy
 import com.android.settingslib.preference.PreferenceScreenCreator
 
 @ProvidePreferenceScreen(LockScreenPreferenceScreen.KEY)
-open class LockScreenPreferenceScreen : PreferenceScreenCreator, PreferenceSummaryProvider {
+open class LockScreenPreferenceScreen(private val context: Context) :
+    AbstractKeyedDataObservable<String>(), PreferenceScreenCreator, PreferenceSummaryProvider {
+
+    private val observer =
+        KeyedObserver<String> { _, _ -> notifyChange(KEY, PreferenceChangeReason.STATE) }
+
     override val key: String
         get() = KEY
 
@@ -39,6 +51,20 @@ open class LockScreenPreferenceScreen : PreferenceScreenCreator, PreferenceSumma
     override val keywords: Int
         get() = R.string.keywords_ambient_display_screen
 
+    override fun onFirstObserverAdded() {
+        val store = SettingsSecureStore.get(context)
+        val executor = HandlerExecutor.main
+        // update summary when lock screen notification settings are changed
+        store.addObserver(LOCK_SCREEN_SHOW_NOTIFICATIONS, observer, executor)
+        store.addObserver(LOCK_SCREEN_ALLOW_PRIVATE_NOTIFICATIONS, observer, executor)
+    }
+
+    override fun onLastObserverRemoved() {
+        val store = SettingsSecureStore.get(context)
+        store.removeObserver(LOCK_SCREEN_SHOW_NOTIFICATIONS, observer)
+        store.removeObserver(LOCK_SCREEN_ALLOW_PRIVATE_NOTIFICATIONS, observer)
+    }
+
     override fun getSummary(context: Context): CharSequence? =
         context.getString(LockScreenNotificationPreferenceController.getSummaryResource(context))