[Catalyst] Refactor DarkModeScreen

By virtue of KeyValueStore abstraction, the per-fragment state could be
moved into storage.

NO_IFTTT=Catalyst only

Bug: 375132235
Flag: com.android.settings.flags.catalyst_dark_ui_mode
Test: Manual
Change-Id: Ifff1c6e0b51cda981337b84008713c35a0a724ea

src/com/android/settings/display/darkmode/DarkModeScreen.kt

@@ -17,24 +17,16 @@
 package com.android.settings.display.darkmode
 
 import android.Manifest
-import android.app.UiModeManager
-import android.content.BroadcastReceiver
 import android.content.Context
-import android.content.Intent
-import android.content.IntentFilter
-import android.content.res.Configuration
 import android.os.PowerManager
 import androidx.preference.Preference
 import com.android.settings.R
 import com.android.settings.flags.Flags
 import com.android.settingslib.PrimarySwitchPreference
 import com.android.settingslib.datastore.KeyValueStore
-import com.android.settingslib.datastore.NoOpKeyedObservable
 import com.android.settingslib.datastore.Permissions
 import com.android.settingslib.metadata.BooleanValue
 import com.android.settingslib.metadata.PersistentPreference
-import com.android.settingslib.metadata.PreferenceLifecycleContext
-import com.android.settingslib.metadata.PreferenceLifecycleProvider
 import com.android.settingslib.metadata.PreferenceMetadata
 import com.android.settingslib.metadata.PreferenceSummaryProvider
 import com.android.settingslib.metadata.ProvidePreferenceScreen
@@ -43,26 +35,17 @@ import com.android.settingslib.metadata.SensitivityLevel
 import com.android.settingslib.metadata.preferenceHierarchy
 import com.android.settingslib.preference.PreferenceScreenBinding
 import com.android.settingslib.preference.PreferenceScreenCreator
-import java.util.WeakHashMap
 
 // LINT.IfChange
 @ProvidePreferenceScreen
-class DarkModeScreen :
+class DarkModeScreen(context: Context) :
     PreferenceScreenCreator,
     PreferenceScreenBinding,
     PersistentPreference<Boolean>,
     BooleanValue,
-    PreferenceSummaryProvider,
-    PreferenceLifecycleProvider {
+    PreferenceSummaryProvider {
 
-    /**
-     * States for different screens.
-     *
-     * The "Dark mode" appears in several screens. And in Android split-screen mode, more than one
-     * "Dark mode" settings could be displayed at the same time. As [PreferenceScreenCreator] works
-     * like singleton, we need to register different broadcast receivers for different screens.
-     */
-    private val fragmentStates = WeakHashMap<PreferenceLifecycleContext, FragmentState>()
+    private val darkModeStorage = DarkModeStorage(context)
 
     override val key: String
         get() = KEY
@@ -99,23 +82,23 @@ class DarkModeScreen :
 
     override fun getPreferenceHierarchy(context: Context) = preferenceHierarchy(this) {}
 
-    override fun storage(context: Context): KeyValueStore = DarkModeStorage(context)
+    override fun storage(context: Context): KeyValueStore = darkModeStorage
 
     override fun createWidget(context: Context) = PrimarySwitchPreference(context)
 
     override fun bind(preference: Preference, metadata: PreferenceMetadata) {
         super.bind(preference, metadata)
         if (preference is DarkModePreference) preference.setCatalystEnabled(true)
-        val context = preference.context
-        val primarySwitchPreference = preference as PrimarySwitchPreference
-        primarySwitchPreference.isSwitchEnabled = !context.isPowerSaveMode()
-        primarySwitchPreference.isChecked = context.isDarkMode()
+        (preference as PrimarySwitchPreference).apply {
+            isSwitchEnabled = isEnabled()
+            isChecked = darkModeStorage.getBoolean(KEY) == true
+        }
     }
 
     override fun isEnabled(context: Context) = !context.isPowerSaveMode()
 
     override fun getSummary(context: Context): CharSequence? {
-        val active = context.isDarkMode()
+        val active = darkModeStorage.getBoolean(KEY) == true
         return when {
             !context.isPowerSaveMode() -> AutoDarkTheme.getStatus(context, active)
             active -> context.getString(R.string.dark_ui_mode_disabled_summary_dark_theme_on)
@@ -123,71 +106,11 @@ class DarkModeScreen :
         }
     }
 
-    override fun onStart(context: PreferenceLifecycleContext) {
-        val broadcastReceiver =
-            object : BroadcastReceiver() {
-                override fun onReceive(receiverContext: Context, intent: Intent) {
-                    context.notifyPreferenceChange(KEY)
-                }
-            }
-        context.registerReceiver(
-            broadcastReceiver,
-            IntentFilter(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED),
-        )
-
-        val darkModeObserver = DarkModeObserver(context)
-        darkModeObserver.subscribe { context.notifyPreferenceChange(KEY) }
-
-        fragmentStates[context] = FragmentState(broadcastReceiver, darkModeObserver)
-    }
-
-    override fun onStop(context: PreferenceLifecycleContext) {
-        fragmentStates.remove(context)?.run {
-            context.unregisterReceiver(broadcastReceiver)
-            darkModeObserver.unsubscribe()
-        }
-    }
-
-    private class FragmentState(
-        val broadcastReceiver: BroadcastReceiver,
-        val darkModeObserver: DarkModeObserver,
-    )
-
-    /**
-     * Abstract storage for dark mode settings.
-     *
-     * The underlying storage is manipulated by [UiModeManager] but we do not need to worry about
-     * the details. Additionally, the observer is for UI purpose only right now, so use
-     * [NoOpKeyedObservable].
-     */
-    @Suppress("UNCHECKED_CAST")
-    private class DarkModeStorage(private val context: Context) :
-        NoOpKeyedObservable<String>(), KeyValueStore {
-
-        override fun contains(key: String) = key == KEY
-
-        override fun <T : Any> getValue(key: String, valueType: Class<T>) =
-            when {
-                key == KEY && valueType == Boolean::class.javaObjectType ->
-                    context.isDarkMode() as T
-                else -> null
-            }
-
-        override fun <T : Any> setValue(key: String, valueType: Class<T>, value: T?) {
-            if (key == KEY && value is Boolean) {
-                context.getSystemService(UiModeManager::class.java)?.setNightModeActivated(value)
-            }
-        }
-    }
-
     companion object {
         const val KEY = "dark_ui_mode"
 
         private fun Context.isPowerSaveMode() =
             getSystemService(PowerManager::class.java)?.isPowerSaveMode == true
-
-        private fun Context.isDarkMode() =
-            (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_YES) != 0
     }
 }
 // LINT.ThenChange(../DarkUIPreferenceController.java)

src/com/android/settings/display/darkmode/DarkModeStorage.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2024 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.display.darkmode
+
+import android.app.UiModeManager
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.content.res.Configuration
+import android.os.PowerManager
+import com.android.settingslib.datastore.AbstractKeyedDataObservable
+import com.android.settingslib.datastore.DataChangeReason
+import com.android.settingslib.datastore.KeyValueStore
+
+/**
+ * Abstract storage for dark mode settings.
+ *
+ * The underlying storage is manipulated by [UiModeManager] but we do not need to worry about the
+ * details.
+ */
+@Suppress("UNCHECKED_CAST")
+internal class DarkModeStorage(private val context: Context) :
+    AbstractKeyedDataObservable<String>(), KeyValueStore {
+    private lateinit var broadcastReceiver: BroadcastReceiver
+    private lateinit var darkModeObserver: DarkModeObserver
+
+    override fun contains(key: String) = true
+
+    override fun <T : Any> getValue(key: String, valueType: Class<T>) = context.isDarkMode() as T
+
+    private fun Context.isDarkMode() =
+        (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_YES) != 0
+
+    override fun <T : Any> setValue(key: String, valueType: Class<T>, value: T?) {
+        context.getSystemService(UiModeManager::class.java)?.setNightModeActivated(value as Boolean)
+    }
+
+    override fun onFirstObserverAdded() {
+        broadcastReceiver =
+            object : BroadcastReceiver() {
+                override fun onReceive(context: Context, intent: Intent) {
+                    notifyChange(DataChangeReason.UPDATE)
+                }
+            }
+        context.registerReceiver(
+            broadcastReceiver,
+            IntentFilter(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED),
+        )
+
+        darkModeObserver = DarkModeObserver(context)
+        darkModeObserver.subscribe { notifyChange(DataChangeReason.UPDATE) }
+    }
+
+    override fun onLastObserverRemoved() {
+        context.unregisterReceiver(broadcastReceiver)
+        darkModeObserver.unsubscribe()
+    }
+}