[Catalyst] Refine DataSaverMainSwitchPreference

Export datastore for preference state monitoring.

Bug: 368359883
Flag: com.android.settings.flags.catalyst
Test: devtool
Change-Id: Ie6b001cdd6a8d27f9cb16d563852ad88b7366916

src/com/android/settings/datausage/DataSaverMainSwitchPreference.kt

@@ -19,18 +19,14 @@ package com.android.settings.datausage
 import android.content.Context
 import com.android.settings.R
 import com.android.settings.widget.MainSwitchBarMetadata
+import com.android.settingslib.datastore.AbstractKeyedDataObservable
+import com.android.settingslib.datastore.DataChangeReason
 import com.android.settingslib.datastore.KeyValueStore
-import com.android.settingslib.datastore.NoOpKeyedObservable
-import com.android.settingslib.metadata.PreferenceLifecycleContext
 import com.android.settingslib.metadata.PreferenceLifecycleProvider
 import com.android.settingslib.metadata.ReadWritePermit
 import com.android.settingslib.metadata.SensitivityLevel
 
-class DataSaverMainSwitchPreference(context: Context) :
-    MainSwitchBarMetadata, PreferenceLifecycleProvider {
-
-    private val dataSaverBackend = DataSaverBackend(context)
-    private var dataSaverBackendListener: DataSaverBackend.Listener? = null
+class DataSaverMainSwitchPreference : MainSwitchBarMetadata, PreferenceLifecycleProvider {
 
     override val key
         get() = KEY
@@ -38,7 +34,7 @@ class DataSaverMainSwitchPreference(context: Context) :
     override val title
         get() = R.string.data_saver_switch_title
 
-    override fun storage(context: Context): KeyValueStore = DataSaverStore(dataSaverBackend)
+    override fun storage(context: Context) = createDataStore(context)
 
     override fun getReadPermit(context: Context, myUid: Int, callingUid: Int) =
         ReadWritePermit.ALLOW
@@ -49,24 +45,11 @@ class DataSaverMainSwitchPreference(context: Context) :
     override val sensitivityLevel
         get() = SensitivityLevel.NO_SENSITIVITY
 
-    override fun onStart(context: PreferenceLifecycleContext) {
-        val listener = DataSaverBackend.Listener { context.notifyPreferenceChange(KEY) }
-        dataSaverBackendListener = listener
-        dataSaverBackend.addListener(listener)
-    }
-
-    override fun onStop(context: PreferenceLifecycleContext) {
-        dataSaverBackendListener?.let {
-            dataSaverBackend.remListener(it)
-            dataSaverBackendListener = null
-        }
-    }
-
     @Suppress("UNCHECKED_CAST")
     private class DataSaverStore(private val dataSaverBackend: DataSaverBackend) :
-        NoOpKeyedObservable<String>(), KeyValueStore {
+        AbstractKeyedDataObservable<String>(), KeyValueStore, DataSaverBackend.Listener {
 
-        override fun contains(key: String) = true // just assume the datastore contains the value
+        override fun contains(key: String) = key == KEY
 
         override fun <T : Any> getValue(key: String, valueType: Class<T>): T? =
             dataSaverBackend.isDataSaverEnabled as T?
@@ -74,9 +57,20 @@ class DataSaverMainSwitchPreference(context: Context) :
         override fun <T : Any> setValue(key: String, valueType: Class<T>, value: T?) {
             dataSaverBackend.isDataSaverEnabled = value as Boolean
         }
+
+        override fun onFirstObserverAdded() = dataSaverBackend.addListener(this)
+
+        override fun onLastObserverRemoved() = dataSaverBackend.remListener(this)
+
+        override fun onDataSaverChanged(isDataSaving: Boolean) =
+            notifyChange(KEY, DataChangeReason.UPDATE)
     }
 
     companion object {
         const val KEY = "use_data_saver"
+
+        /** Creates [KeyValueStore] for data saver preference. */
+        fun createDataStore(context: Context): KeyValueStore =
+            DataSaverStore(DataSaverBackend(context))
     }
 }

src/com/android/settings/datausage/DataSaverScreen.kt

@@ -19,24 +19,30 @@ package com.android.settings.datausage
 import android.content.Context
 import android.telephony.SubscriptionManager.INVALID_SUBSCRIPTION_ID
 import com.android.settings.R
+import com.android.settings.Settings.DataSaverSummaryActivity
 import com.android.settings.flags.Flags
+import com.android.settings.utils.makeLaunchIntent
+import com.android.settingslib.datastore.HandlerExecutor
+import com.android.settingslib.datastore.KeyedObserver
 import com.android.settingslib.metadata.PreferenceAvailabilityProvider
 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
 import com.android.settingslib.metadata.preferenceHierarchy
 import com.android.settingslib.preference.PreferenceScreenCreator
+import com.android.settings.datausage.DataSaverMainSwitchPreference.Companion.KEY as DATA_SAVER_KEY
 
 @ProvidePreferenceScreen
-class DataSaverScreen :
+class DataSaverScreen(context: Context) :
     PreferenceScreenCreator,
     PreferenceAvailabilityProvider,
     PreferenceSummaryProvider,
     PreferenceLifecycleProvider {
 
-    private var dataSaverBackend: DataSaverBackend? = null
-    private var dataSaverBackendListener: DataSaverBackend.Listener? = null
+    private val dataSaverStore = DataSaverMainSwitchPreference.createDataStore(context)
+    private lateinit var keyedObserver: KeyedObserver<String>
 
     override val key
         get() = KEY
@@ -53,7 +59,7 @@ class DataSaverScreen :
 
     override fun getSummary(context: Context): CharSequence? =
         when {
-            DataSaverBackend(context).isDataSaverEnabled ->
+            dataSaverStore.getBoolean(DATA_SAVER_KEY) == true ->
                 context.getString(R.string.data_saver_on)
             else -> context.getString(R.string.data_saver_off)
         }
@@ -65,21 +71,21 @@ class DataSaverScreen :
 
     override fun fragmentClass() = DataSaverSummary::class.java
 
+    override fun getLaunchIntent(context: Context, metadata: PreferenceMetadata?) =
+        makeLaunchIntent(context, DataSaverSummaryActivity::class.java, metadata?.key)
+
     override fun getPreferenceHierarchy(context: Context) =
-        preferenceHierarchy(this) { +DataSaverMainSwitchPreference(context) }
+        preferenceHierarchy(this) { +DataSaverMainSwitchPreference() }
 
     override fun hasCompleteHierarchy() = false
 
-    override fun onStart(context: PreferenceLifecycleContext) {
-        val listener = DataSaverBackend.Listener { context.notifyPreferenceChange(KEY) }
-        dataSaverBackendListener = listener
-        dataSaverBackend = DataSaverBackend(context).apply { addListener(listener) }
+    override fun onCreate(context: PreferenceLifecycleContext) {
+        keyedObserver = KeyedObserver { _, _ -> context.notifyPreferenceChange(KEY) }
+        dataSaverStore.addObserver(DATA_SAVER_KEY, keyedObserver, HandlerExecutor.main)
     }
 
-    override fun onStop(context: PreferenceLifecycleContext) {
-        dataSaverBackend?.remListener(dataSaverBackendListener)
-        dataSaverBackend = null
-        dataSaverBackendListener = null
+    override fun onDestroy(context: PreferenceLifecycleContext) {
+        dataSaverStore.removeObserver(DATA_SAVER_KEY, keyedObserver)
     }
 
     companion object {

tests/robotests/src/com/android/settings/datausage/DataSaverScreenTest.kt

@@ -16,13 +16,16 @@
 
 package com.android.settings.datausage
 
+import androidx.test.core.app.ApplicationProvider
 import com.android.settings.flags.Flags
 import com.android.settingslib.preference.CatalystScreenTestCase
 import com.google.common.truth.Truth.assertThat
 import org.junit.Test
 
 class DataSaverScreenTest : CatalystScreenTestCase() {
-    override val preferenceScreenCreator = DataSaverScreen()
+    override val preferenceScreenCreator =
+        DataSaverScreen(ApplicationProvider.getApplicationContext())
+
     override val flagName
         get() = Flags.FLAG_CATALYST_RESTRICT_BACKGROUND_PARENT_ENTRY