Update System settings content observer to cache values.

Existing ContentObserver will cache values and overwrite
them when the value itself is modified or caller force
updates.

Bug: 149571513
Test: Wrote unit tests, mostly for caching logic.
Not meant to test ContentObserver contract for registering an
observer.

Change-Id: I12835f6c2be27ce17f65a55c51c4ef85c63b4487
diff --git a/src/com/android/launcher3/LauncherAppState.java b/src/com/android/launcher3/LauncherAppState.java
index a4181c5..57d7600 100644
--- a/src/com/android/launcher3/LauncherAppState.java
+++ b/src/com/android/launcher3/LauncherAppState.java
@@ -17,8 +17,8 @@
 package com.android.launcher3;
 
 import static com.android.launcher3.InvariantDeviceProfile.CHANGE_FLAG_ICON_PARAMS;
+import static com.android.launcher3.util.SettingsCache.NOTIFICATION_BADGING_URI;
 import static com.android.launcher3.util.Executors.MODEL_EXECUTOR;
-import static com.android.launcher3.util.SecureSettingsObserver.newNotificationSettingsObserver;
 
 import android.content.ComponentName;
 import android.content.Context;
@@ -37,10 +37,10 @@
 import com.android.launcher3.pm.InstallSessionHelper;
 import com.android.launcher3.pm.InstallSessionTracker;
 import com.android.launcher3.pm.UserCache;
+import com.android.launcher3.util.SettingsCache;
 import com.android.launcher3.util.MainThreadInitializedObject;
 import com.android.launcher3.util.Preconditions;
 import com.android.launcher3.util.SafeCloseable;
-import com.android.launcher3.util.SecureSettingsObserver;
 import com.android.launcher3.util.SimpleBroadcastReceiver;
 import com.android.launcher3.widget.custom.CustomWidgetManager;
 
@@ -57,8 +57,9 @@
     private final IconCache mIconCache;
     private final WidgetPreviewLoader mWidgetCache;
     private final InvariantDeviceProfile mInvariantDeviceProfile;
+    private SettingsCache.OnChangeListener mNotificationSettingsChangedListener;
 
-    private SecureSettingsObserver mNotificationDotsObserver;
+    private SettingsCache mSettingsCache;
     private InstallSessionTracker mInstallSessionTracker;
     private SimpleBroadcastReceiver mModelChangeReceiver;
     private SafeCloseable mCalendarChangeTracker;
@@ -108,10 +109,11 @@
                 .registerInstallTracker(mModel);
 
         // Register an observer to rebind the notification listener when dots are re-enabled.
-        mNotificationDotsObserver =
-                newNotificationSettingsObserver(mContext, this::onNotificationSettingsChanged);
-        mNotificationDotsObserver.register();
-        mNotificationDotsObserver.dispatchOnChange();
+        mSettingsCache = SettingsCache.INSTANCE.get(mContext);
+        mNotificationSettingsChangedListener = this::onNotificationSettingsChanged;
+        mSettingsCache.register(NOTIFICATION_BADGING_URI,
+                mNotificationSettingsChangedListener);
+        mSettingsCache.dispatchOnChange(NOTIFICATION_BADGING_URI);
     }
 
     public LauncherAppState(Context context, @Nullable String iconCacheFileName) {
@@ -166,8 +168,9 @@
         }
         CustomWidgetManager.INSTANCE.get(mContext).setWidgetRefreshCallback(null);
 
-        if (mNotificationDotsObserver != null) {
-            mNotificationDotsObserver.unregister();
+        if (mSettingsCache != null) {
+            mSettingsCache.unregister(NOTIFICATION_BADGING_URI,
+                    mNotificationSettingsChangedListener);
         }
     }
 
diff --git a/src/com/android/launcher3/notification/NotificationListener.java b/src/com/android/launcher3/notification/NotificationListener.java
index 059ad18..2905dc3 100644
--- a/src/com/android/launcher3/notification/NotificationListener.java
+++ b/src/com/android/launcher3/notification/NotificationListener.java
@@ -16,9 +16,9 @@
 
 package com.android.launcher3.notification;
 
+import static com.android.launcher3.util.SettingsCache.NOTIFICATION_BADGING_URI;
 import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
 import static com.android.launcher3.util.Executors.MODEL_EXECUTOR;
-import static com.android.launcher3.util.SecureSettingsObserver.newNotificationSettingsObserver;
 
 import android.annotation.TargetApi;
 import android.app.Notification;
@@ -37,8 +37,8 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
+import com.android.launcher3.util.SettingsCache;
 import com.android.launcher3.util.PackageUserKey;
-import com.android.launcher3.util.SecureSettingsObserver;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -81,7 +81,8 @@
     /** The last notification key that was dismissed from launcher UI */
     private String mLastKeyDismissedByLauncher;
 
-    private SecureSettingsObserver mNotificationDotsObserver;
+    private SettingsCache mSettingsCache;
+    private SettingsCache.OnChangeListener mNotificationSettingsChangedListener;
 
     public NotificationListener() {
         mWorkerHandler = new Handler(MODEL_EXECUTOR.getLooper(), this::handleWorkerMessage);
@@ -207,10 +208,12 @@
         super.onListenerConnected();
         sIsConnected = true;
 
-        mNotificationDotsObserver =
-                newNotificationSettingsObserver(this, this::onNotificationSettingsChanged);
-        mNotificationDotsObserver.register();
-        mNotificationDotsObserver.dispatchOnChange();
+        // Register an observer to rebind the notification listener when dots are re-enabled.
+        mSettingsCache = SettingsCache.INSTANCE.get(this);
+        mNotificationSettingsChangedListener = this::onNotificationSettingsChanged;
+        mSettingsCache.register(NOTIFICATION_BADGING_URI,
+                mNotificationSettingsChangedListener);
+        mSettingsCache.dispatchOnChange(NOTIFICATION_BADGING_URI);
 
         onNotificationFullRefresh();
     }
@@ -229,7 +232,7 @@
     public void onListenerDisconnected() {
         super.onListenerDisconnected();
         sIsConnected = false;
-        mNotificationDotsObserver.unregister();
+        mSettingsCache.unregister(NOTIFICATION_BADGING_URI, mNotificationSettingsChangedListener);
         onNotificationFullRefresh();
     }
 
diff --git a/src/com/android/launcher3/settings/NotificationDotsPreference.java b/src/com/android/launcher3/settings/NotificationDotsPreference.java
index a91303a..a354169 100644
--- a/src/com/android/launcher3/settings/NotificationDotsPreference.java
+++ b/src/com/android/launcher3/settings/NotificationDotsPreference.java
@@ -35,14 +35,14 @@
 
 import com.android.launcher3.R;
 import com.android.launcher3.notification.NotificationListener;
-import com.android.launcher3.util.SecureSettingsObserver;
+import com.android.launcher3.util.SettingsCache;
 
 /**
  * A {@link Preference} for indicating notification dots status.
  * Also has utility methods for updating UI based on dots status changes.
  */
 public class NotificationDotsPreference extends Preference
-        implements SecureSettingsObserver.OnChangeListener {
+        implements SettingsCache.OnChangeListener {
 
     private boolean mWidgetFrameVisible = false;
 
diff --git a/src/com/android/launcher3/settings/SettingsActivity.java b/src/com/android/launcher3/settings/SettingsActivity.java
index 922425f..ac8dac5 100644
--- a/src/com/android/launcher3/settings/SettingsActivity.java
+++ b/src/com/android/launcher3/settings/SettingsActivity.java
@@ -18,13 +18,13 @@
 
 import static androidx.core.view.accessibility.AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS;
 
+import static com.android.launcher3.util.SettingsCache.NOTIFICATION_BADGING_URI;
+import static com.android.launcher3.util.SettingsCache.NOTIFICATION_ENABLED_LISTENERS;
 import static com.android.launcher3.states.RotationHelper.ALLOW_ROTATION_PREFERENCE_KEY;
 import static com.android.launcher3.states.RotationHelper.getAllowRotationDefaultValue;
-import static com.android.launcher3.util.SecureSettingsObserver.newNotificationSettingsObserver;
 
 import android.content.SharedPreferences;
 import android.os.Bundle;
-import android.provider.Settings;
 import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
@@ -45,8 +45,8 @@
 import com.android.launcher3.Utilities;
 import com.android.launcher3.config.FeatureFlags;
 import com.android.launcher3.model.WidgetsModel;
+import com.android.launcher3.util.SettingsCache;
 import com.android.launcher3.uioverrides.plugins.PluginManagerWrapper;
-import com.android.launcher3.util.SecureSettingsObserver;
 
 /**
  * Settings activity for Launcher. Currently implements the following setting: Allow rotation
@@ -59,8 +59,6 @@
     private static final String FLAGS_PREFERENCE_KEY = "flag_toggler";
 
     private static final String NOTIFICATION_DOTS_PREFERENCE_KEY = "pref_icon_badging";
-    /** Hidden field Settings.Secure.ENABLED_NOTIFICATION_LISTENERS */
-    private static final String NOTIFICATION_ENABLED_LISTENERS = "enabled_notification_listeners";
 
     public static final String EXTRA_FRAGMENT_ARG_KEY = ":settings:fragment_args_key";
     public static final String EXTRA_SHOW_FRAGMENT_ARGS = ":settings:show_fragment_args";
@@ -126,10 +124,11 @@
      */
     public static class LauncherSettingsFragment extends PreferenceFragmentCompat {
 
-        private SecureSettingsObserver mNotificationDotsObserver;
+        private SettingsCache mSettingsCache;
 
         private String mHighLightKey;
         private boolean mPreferenceHighlighted = false;
+        private NotificationDotsPreference mNotificationSettingsChangedListener;
 
         @Override
         public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
@@ -177,14 +176,16 @@
                     }
 
                     // Listen to system notification dot settings while this UI is active.
-                    mNotificationDotsObserver = newNotificationSettingsObserver(
-                            getActivity(), (NotificationDotsPreference) preference);
-                    mNotificationDotsObserver.register();
+                    mSettingsCache = SettingsCache.INSTANCE.get(getActivity());
+                    mNotificationSettingsChangedListener =
+                            ((NotificationDotsPreference) preference);
+                    mSettingsCache.register(NOTIFICATION_BADGING_URI,
+                            (NotificationDotsPreference) mNotificationSettingsChangedListener);
                     // Also listen if notification permission changes
-                    mNotificationDotsObserver.getResolver().registerContentObserver(
-                            Settings.Secure.getUriFor(NOTIFICATION_ENABLED_LISTENERS), false,
-                            mNotificationDotsObserver);
-                    mNotificationDotsObserver.dispatchOnChange();
+                    mSettingsCache.register(NOTIFICATION_ENABLED_LISTENERS,
+                            mNotificationSettingsChangedListener);
+                    mSettingsCache.dispatchOnChange(NOTIFICATION_BADGING_URI);
+                    mSettingsCache.dispatchOnChange(NOTIFICATION_ENABLED_LISTENERS);
                     return true;
 
                 case ALLOW_ROTATION_PREFERENCE_KEY:
@@ -251,9 +252,11 @@
 
         @Override
         public void onDestroy() {
-            if (mNotificationDotsObserver != null) {
-                mNotificationDotsObserver.unregister();
-                mNotificationDotsObserver = null;
+            if (mSettingsCache != null) {
+                mSettingsCache.unregister(NOTIFICATION_BADGING_URI,
+                        mNotificationSettingsChangedListener);
+                mSettingsCache.unregister(NOTIFICATION_ENABLED_LISTENERS,
+                        mNotificationSettingsChangedListener);
             }
             super.onDestroy();
         }
diff --git a/src/com/android/launcher3/util/SecureSettingsObserver.java b/src/com/android/launcher3/util/SecureSettingsObserver.java
deleted file mode 100644
index 9fe72ad..0000000
--- a/src/com/android/launcher3/util/SecureSettingsObserver.java
+++ /dev/null
@@ -1,104 +0,0 @@
-/*
- * Copyright (C) 2017 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.launcher3.util;
-
-import android.content.ContentResolver;
-import android.content.Context;
-import android.database.ContentObserver;
-import android.os.Handler;
-import android.provider.Settings;
-
-/**
- * Utility class to listen for secure settings changes
- */
-public class SecureSettingsObserver extends ContentObserver {
-
-    /** Hidden field Settings.Secure.NOTIFICATION_BADGING */
-    public static final String NOTIFICATION_BADGING = "notification_badging";
-    /** Hidden field Settings.Secure.ONE_HANDED_MODE_ENABLED */
-    public static final String ONE_HANDED_ENABLED = "one_handed_mode_enabled";
-    /** Hidden field Settings.Secure.SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED */
-    public static final String ONE_HANDED_SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED =
-            "swipe_bottom_to_notification_enabled";
-
-    private final ContentResolver mResolver;
-    private final String mKeySetting;
-    private final int mDefaultValue;
-    private final OnChangeListener mOnChangeListener;
-
-    public SecureSettingsObserver(ContentResolver resolver, OnChangeListener listener,
-            String keySetting, int defaultValue) {
-        super(new Handler());
-
-        mResolver = resolver;
-        mOnChangeListener = listener;
-        mKeySetting = keySetting;
-        mDefaultValue = defaultValue;
-    }
-
-    @Override
-    public void onChange(boolean selfChange) {
-        mOnChangeListener.onSettingsChanged(getValue());
-    }
-
-    public boolean getValue() {
-        return Settings.Secure.getInt(mResolver, mKeySetting, mDefaultValue) == 1;
-    }
-
-    public void register() {
-        mResolver.registerContentObserver(Settings.Secure.getUriFor(mKeySetting), false, this);
-    }
-
-    public ContentResolver getResolver() {
-        return mResolver;
-    }
-
-    public void dispatchOnChange() {
-        onChange(true);
-    }
-
-    public void unregister() {
-        mResolver.unregisterContentObserver(this);
-    }
-
-    public interface OnChangeListener {
-        void onSettingsChanged(boolean isEnabled);
-    }
-
-    public static SecureSettingsObserver newNotificationSettingsObserver(Context context,
-            OnChangeListener listener) {
-        return new SecureSettingsObserver(
-                context.getContentResolver(), listener, NOTIFICATION_BADGING, 1);
-    }
-
-    public static SecureSettingsObserver newOneHandedSettingsObserver(Context context,
-            OnChangeListener listener) {
-        return new SecureSettingsObserver(
-                context.getContentResolver(), listener, ONE_HANDED_ENABLED, 0);
-    }
-
-    /**
-     * Constructs settings observer for {@link #ONE_HANDED_SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED}
-     * preference.
-     */
-    public static SecureSettingsObserver newSwipeToNotificationSettingsObserver(Context context,
-            OnChangeListener listener) {
-        return new SecureSettingsObserver(
-                context.getContentResolver(), listener,
-                ONE_HANDED_SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED, 1);
-    }
-}
diff --git a/src/com/android/launcher3/util/SettingsCache.java b/src/com/android/launcher3/util/SettingsCache.java
new file mode 100644
index 0000000..22b4d38
--- /dev/null
+++ b/src/com/android/launcher3/util/SettingsCache.java
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2021 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.launcher3.util;
+
+import static android.provider.Settings.System.ACCELEROMETER_ROTATION;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.database.ContentObserver;
+import android.net.Uri;
+import android.os.Handler;
+import android.provider.Settings;
+
+import androidx.annotation.VisibleForTesting;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * ContentObserver over Settings keys that also has a caching layer.
+ * Consumers can register for callbacks via {@link #register(Uri, OnChangeListener)} and
+ * {@link #unregister(Uri, OnChangeListener)} methods.
+ *
+ * This can be used as a normal cache without any listeners as well via the
+ * {@link #getValue(Uri, int)} and {@link #dispatchOnChange(Uri)} to update (and subsequently call
+ * get)
+ *
+ * The cache will be invalidated/updated through the normal
+ * {@link ContentObserver#onChange(boolean)} calls
+ * or can be force updated by calling {@link #dispatchOnChange(Uri)}.
+ *
+ * Cache will also be updated if a key queried is missing (even if it has no listeners registered).
+ */
+public class SettingsCache extends ContentObserver {
+
+    /** Hidden field Settings.Secure.NOTIFICATION_BADGING */
+    public static final Uri NOTIFICATION_BADGING_URI =
+            Settings.Secure.getUriFor("notification_badging");
+    /** Hidden field Settings.Secure.ONE_HANDED_MODE_ENABLED */
+    public static final String ONE_HANDED_ENABLED = "one_handed_mode_enabled";
+    /** Hidden field Settings.Secure.SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED */
+    public static final String ONE_HANDED_SWIPE_BOTTOM_TO_NOTIFICATION_ENABLED =
+            "swipe_bottom_to_notification_enabled";
+    /** Hidden field Settings.Secure.ENABLED_NOTIFICATION_LISTENERS */
+    public static final Uri NOTIFICATION_ENABLED_LISTENERS =
+            Settings.Secure.getUriFor("enabled_notification_listeners");
+    public static final Uri ROTATION_SETTING_URI =
+            Settings.System.getUriFor(ACCELEROMETER_ROTATION);
+
+    private static final String SYSTEM_URI_PREFIX = Settings.System.CONTENT_URI.toString();
+
+    /**
+     * Caches the last seen value for registered keys.
+     */
+    private Map<Uri, Boolean> mKeyCache = new ConcurrentHashMap<>();
+    private final Map<Uri, CopyOnWriteArrayList<OnChangeListener>> mListenerMap = new HashMap<>();
+    protected final ContentResolver mResolver;
+
+
+    /**
+     * Singleton instance
+     */
+    public static MainThreadInitializedObject<SettingsCache> INSTANCE =
+            new MainThreadInitializedObject<>(SettingsCache::new);
+
+    private SettingsCache(Context context) {
+        super(new Handler());
+        mResolver = context.getContentResolver();
+    }
+
+    @Override
+    public void onChange(boolean selfChange, Uri uri) {
+        // We use default of 1, but if we're getting an onChange call, can assume a non-default
+        // value will exist
+        boolean newVal = updateValue(uri, 1 /* Effectively Unused */);
+        if (!mListenerMap.containsKey(uri)) {
+            return;
+        }
+
+        for (OnChangeListener listener : mListenerMap.get(uri)) {
+            listener.onSettingsChanged(newVal);
+        }
+    }
+
+    /**
+     * Returns the value for this classes key from the cache. If not in cache, will call
+     * {@link #updateValue(Uri, int)} to fetch.
+     */
+    public boolean getValue(Uri keySetting, int defaultValue) {
+        if (mKeyCache.containsKey(keySetting)) {
+            return mKeyCache.get(keySetting);
+        } else {
+            return updateValue(keySetting, defaultValue);
+        }
+    }
+
+    /**
+     * Does not de-dupe if you add same listeners for the same key multiple times.
+     * Unregister once complete using {@link #unregister(Uri, OnChangeListener)}
+     */
+    public void register(Uri uri, OnChangeListener changeListener) {
+        if (mListenerMap.containsKey(uri)) {
+            mListenerMap.get(uri).add(changeListener);
+        } else {
+            CopyOnWriteArrayList<OnChangeListener> l = new CopyOnWriteArrayList<>();
+            l.add(changeListener);
+            mListenerMap.put(uri, l);
+            mResolver.registerContentObserver(uri, false, this);
+        }
+    }
+
+    private boolean updateValue(Uri keyUri, int defaultValue) {
+        String key = keyUri.getLastPathSegment();
+        boolean newVal;
+        if (keyUri.toString().startsWith(SYSTEM_URI_PREFIX)) {
+            newVal = Settings.System.getInt(mResolver, key, defaultValue) == 1;
+        } else { // SETTING_SECURE
+            newVal = Settings.Secure.getInt(mResolver, key, defaultValue) == 1;
+        }
+
+        mKeyCache.put(keyUri, newVal);
+        return newVal;
+    }
+
+    /**
+     * Force update a change for a given URI and have all listeners for that URI receive callbacks
+     * even if the value is unchanged.
+     */
+    public void dispatchOnChange(Uri uri) {
+        onChange(true, uri);
+    }
+
+    /**
+     * Call to stop receiving updates on the given {@param listener}.
+     * This Uri/Listener pair must correspond to the same pair called with for
+     * {@link #register(Uri, OnChangeListener)}
+     */
+    public void unregister(Uri uri, OnChangeListener listener) {
+        List<OnChangeListener> listenersToRemoveFrom = mListenerMap.get(uri);
+        if (!listenersToRemoveFrom.contains(listener)) {
+            return;
+        }
+
+        listenersToRemoveFrom.remove(listener);
+        if (listenersToRemoveFrom.isEmpty()) {
+            mListenerMap.remove(uri);
+        }
+    }
+
+    /**
+     * Don't use this. Ever.
+     * @param keyCache Cache to replace {@link #mKeyCache}
+     */
+    @VisibleForTesting
+    void setKeyCache(Map<Uri, Boolean> keyCache) {
+        mKeyCache = keyCache;
+    }
+
+    public interface OnChangeListener {
+        void onSettingsChanged(boolean isEnabled);
+    }
+}