Add app-locales backup helper to SystemBackupAgent.

Bug: 203266143
Test: Manual testing on the device by looking at the logs.
Change-Id: I33d13a7c49a4f26431faa747b6910161b41bac3a

services/core/java/com/android/server/backup/AppSpecificLocalesBackupHelper.java

@@ -0,0 +1,90 @@
+/*
+ * 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.server.backup;
+
+import android.annotation.NonNull;
+import android.annotation.UserIdInt;
+import android.app.backup.BlobBackupHelper;
+import android.util.Slog;
+
+import com.android.server.LocalServices;
+import com.android.server.locales.LocaleManagerInternal;
+
+/**
+ * Helper for backing up app-specific locales.
+ * <p>
+ * This helper is used in {@link com.android.server.backup.SystemBackupAgent}
+ */
+public class AppSpecificLocalesBackupHelper extends BlobBackupHelper {
+    private static final String TAG = "AppLocalesBackupHelper";   // must be < 23 chars
+    private static final boolean DEBUG = false;
+
+    // Current version of the blob schema
+    private static final int BLOB_VERSION = 1;
+
+    // Key under which the payload blob is stored
+    private static final String KEY_APP_LOCALES = "app_locales";
+
+    private final @UserIdInt int mUserId;
+
+    private final @NonNull LocaleManagerInternal mLocaleManagerInternal;
+
+    public AppSpecificLocalesBackupHelper(int userId) {
+        super(BLOB_VERSION, KEY_APP_LOCALES);
+        mUserId = userId;
+        mLocaleManagerInternal = LocalServices.getService(LocaleManagerInternal.class);
+    }
+
+    @Override
+    protected byte[] getBackupPayload(String key) {
+        if (DEBUG) {
+            Slog.d(TAG, "Handling backup of " + key);
+        }
+
+        byte[] newPayload = null;
+        if (KEY_APP_LOCALES.equals(key)) {
+            try {
+                newPayload = mLocaleManagerInternal.getBackupPayload(mUserId);
+            } catch (Exception e) {
+                // Treat as no data
+                Slog.e(TAG, "Couldn't communicate with locale manager", e);
+                newPayload = null;
+            }
+        } else {
+            Slog.w(TAG, "Unexpected backup key " + key);
+        }
+        return newPayload;
+    }
+
+    @Override
+    protected void applyRestoredPayload(String key, byte[] payload) {
+        if (DEBUG) {
+            Slog.d(TAG, "Handling restore of " + key);
+        }
+
+        if (KEY_APP_LOCALES.equals(key)) {
+            try {
+                mLocaleManagerInternal.stageAndApplyRestoredPayload(payload, mUserId);
+            } catch (Exception e) {
+                Slog.e(TAG, "Couldn't communicate with locale manager", e);
+            }
+        } else {
+            Slog.w(TAG, "Unexpected restore key " + key);
+        }
+    }
+
+}

services/core/java/com/android/server/backup/SystemBackupAgent.java

@@ -57,6 +57,7 @@ public class SystemBackupAgent extends BackupAgentHelper {
     private static final String ACCOUNT_MANAGER_HELPER = "account_manager";
     private static final String SLICES_HELPER = "slices";
     private static final String PEOPLE_HELPER = "people";
+    private static final String APP_LOCALES_HELPER = "app_locales";
 
     // These paths must match what the WallpaperManagerService uses.  The leaf *_FILENAME
     // are also used in the full-backup file format, so must not change unless steps are
@@ -83,7 +84,7 @@ public class SystemBackupAgent extends BackupAgentHelper {
     private static final String WALLPAPER_IMAGE_KEY = WallpaperBackupHelper.WALLPAPER_IMAGE_KEY;
 
     private static final Set<String> sEligibleForMultiUser = Sets.newArraySet(
-            PERMISSION_HELPER, NOTIFICATION_HELPER, SYNC_SETTINGS_HELPER);
+            PERMISSION_HELPER, NOTIFICATION_HELPER, SYNC_SETTINGS_HELPER, APP_LOCALES_HELPER);
 
     private int mUserId = UserHandle.USER_SYSTEM;
 
@@ -102,6 +103,7 @@ public class SystemBackupAgent extends BackupAgentHelper {
         addHelper(ACCOUNT_MANAGER_HELPER, new AccountManagerBackupHelper());
         addHelper(SLICES_HELPER, new SliceBackupHelper(this));
         addHelper(PEOPLE_HELPER, new PeopleBackupHelper(mUserId));
+        addHelper(APP_LOCALES_HELPER, new AppSpecificLocalesBackupHelper(mUserId));
     }
 
     @Override