core/java/com/android/server/backup/AccountSyncSettingsBackupHelper.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2014 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 org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 import android.accounts.Account;
 import android.accounts.AccountManager;
 import android.app.backup.BackupDataInputStream;
 import android.app.backup.BackupDataOutput;
 import android.app.backup.BackupHelper;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.SyncAdapterType;
 import android.content.SyncStatusObserver;
 import android.os.Bundle;
 import android.os.ParcelFileDescriptor;
 import android.util.Log;

 import java.io.BufferedOutputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.EOFException;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;

 /**
  * Helper for backing up account sync settings (whether or not a service should be synced). The
  * sync settings are backed up as a JSON object containing all the necessary information for
  * restoring the sync settings later.
  */
 public class AccountSyncSettingsBackupHelper implements BackupHelper {

     private static final String TAG = "AccountSyncSettingsBackupHelper";
     private static final boolean DEBUG = false;

     private static final int STATE_VERSION = 1;
     private static final int MD5_BYTE_SIZE = 16;
     private static final int SYNC_REQUEST_LATCH_TIMEOUT_SECONDS = 1;

     private static final String JSON_FORMAT_HEADER_KEY = "account_data";
     private static final String JSON_FORMAT_ENCODING = "UTF-8";
     private static final int JSON_FORMAT_VERSION = 1;

     private static final String KEY_VERSION = "version";
     private static final String KEY_MASTER_SYNC_ENABLED = "masterSyncEnabled";
     private static final String KEY_ACCOUNTS = "accounts";
     private static final String KEY_ACCOUNT_NAME = "name";
     private static final String KEY_ACCOUNT_TYPE = "type";
     private static final String KEY_ACCOUNT_AUTHORITIES = "authorities";
     private static final String KEY_AUTHORITY_NAME = "name";
     private static final String KEY_AUTHORITY_SYNC_STATE = "syncState";
     private static final String KEY_AUTHORITY_SYNC_ENABLED = "syncEnabled";

     private Context mContext;
     private AccountManager mAccountManager;

     public AccountSyncSettingsBackupHelper(Context context) {
         mContext = context;
         mAccountManager = AccountManager.get(mContext);
     }

     /**
      * Take a snapshot of the current account sync settings and write them to the given output.
      */
     @Override
     public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput output,
             ParcelFileDescriptor newState) {
         try {
             JSONObject dataJSON = serializeAccountSyncSettingsToJSON();

             if (DEBUG) {
                 Log.d(TAG, "Account sync settings JSON: " + dataJSON);
             }

             // Encode JSON data to bytes.
             byte[] dataBytes = dataJSON.toString().getBytes(JSON_FORMAT_ENCODING);
             byte[] oldMd5Checksum = readOldMd5Checksum(oldState);
             byte[] newMd5Checksum = generateMd5Checksum(dataBytes);
             if (!Arrays.equals(oldMd5Checksum, newMd5Checksum)) {
                 int dataSize = dataBytes.length;
                 output.writeEntityHeader(JSON_FORMAT_HEADER_KEY, dataSize);
                 output.writeEntityData(dataBytes, dataSize);

                 Log.i(TAG, "Backup successful.");
             } else {
                 Log.i(TAG, "Old and new MD5 checksums match. Skipping backup.");
             }

             writeNewMd5Checksum(newState, newMd5Checksum);
         } catch (JSONException | IOException | NoSuchAlgorithmException e) {
             Log.e(TAG, "Couldn't backup account sync settings\n" + e);
         }
     }

     /**
      * Fetch and serialize Account and authority information as a JSON Array.
      */
     private JSONObject serializeAccountSyncSettingsToJSON() throws JSONException {
         Account[] accounts = mAccountManager.getAccounts();
         SyncAdapterType[] syncAdapters = ContentResolver.getSyncAdapterTypesAsUser(
                 mContext.getUserId());

         // Create a map of Account types to authorities. Later this will make it easier for us to
         // generate our JSON.
         HashMap<String, List<String>> accountTypeToAuthorities = new HashMap<String,
                 List<String>>();
         for (SyncAdapterType syncAdapter : syncAdapters) {
             // Skip adapters that aren’t visible to the user.
             if (!syncAdapter.isUserVisible()) {
                 continue;
             }
             if (!accountTypeToAuthorities.containsKey(syncAdapter.accountType)) {
                 accountTypeToAuthorities.put(syncAdapter.accountType, new ArrayList<String>());
             }
             accountTypeToAuthorities.get(syncAdapter.accountType).add(syncAdapter.authority);
         }

         // Generate JSON.
         JSONObject backupJSON = new JSONObject();
         backupJSON.put(KEY_VERSION, JSON_FORMAT_VERSION);
         backupJSON.put(KEY_MASTER_SYNC_ENABLED, ContentResolver.getMasterSyncAutomatically());

         JSONArray accountJSONArray = new JSONArray();
         for (Account account : accounts) {
             List<String> authorities = accountTypeToAuthorities.get(account.type);

             // We ignore Accounts that don't have any authorities because there would be no sync
             // settings for us to restore.
             if (authorities == null || authorities.isEmpty()) {
                 continue;
             }

             JSONObject accountJSON = new JSONObject();
             accountJSON.put(KEY_ACCOUNT_NAME, account.name);
             accountJSON.put(KEY_ACCOUNT_TYPE, account.type);

             // Add authorities for this Account type and check whether or not sync is enabled.
             JSONArray authoritiesJSONArray = new JSONArray();
             for (String authority : authorities) {
                 int syncState = ContentResolver.getIsSyncable(account, authority);
                 boolean syncEnabled = ContentResolver.getSyncAutomatically(account, authority);

                 JSONObject authorityJSON = new JSONObject();
                 authorityJSON.put(KEY_AUTHORITY_NAME, authority);
                 authorityJSON.put(KEY_AUTHORITY_SYNC_STATE, syncState);
                 authorityJSON.put(KEY_AUTHORITY_SYNC_ENABLED, syncEnabled);
                 authoritiesJSONArray.put(authorityJSON);
             }
             accountJSON.put(KEY_ACCOUNT_AUTHORITIES, authoritiesJSONArray);

             accountJSONArray.put(accountJSON);
         }
         backupJSON.put(KEY_ACCOUNTS, accountJSONArray);

         return backupJSON;
     }

     /**
      * Read the MD5 checksum from the old state.
      *
      * @return the old MD5 checksum
      */
     private byte[] readOldMd5Checksum(ParcelFileDescriptor oldState) throws IOException {
         DataInputStream dataInput = new DataInputStream(
                 new FileInputStream(oldState.getFileDescriptor()));

         byte[] oldMd5Checksum = new byte[MD5_BYTE_SIZE];
         try {
             int stateVersion = dataInput.readInt();
             if (stateVersion <= STATE_VERSION) {
                 // If the state version is a version we can understand then read the MD5 sum,
                 // otherwise we return an empty byte array for the MD5 sum which will force a
                 // backup.
                 for (int i = 0; i < MD5_BYTE_SIZE; i++) {
                     oldMd5Checksum[i] = dataInput.readByte();
                 }
             } else {
                 Log.i(TAG, "Backup state version is: " + stateVersion
                         + " (support only up to version " + STATE_VERSION + ")");
             }
         } catch (EOFException eof) {
             // Initial state may be empty.
         } finally {
             dataInput.close();
         }
         return oldMd5Checksum;
     }

     /**
      * Write the given checksum to the file descriptor.
      */
     private void writeNewMd5Checksum(ParcelFileDescriptor newState, byte[] md5Checksum)
             throws IOException {
         DataOutputStream dataOutput = new DataOutputStream(
                 new BufferedOutputStream(new FileOutputStream(newState.getFileDescriptor())));

         dataOutput.writeInt(STATE_VERSION);
         dataOutput.write(md5Checksum);
         dataOutput.close();
     }

     private byte[] generateMd5Checksum(byte[] data) throws NoSuchAlgorithmException {
         if (data == null) {
             return null;
         }

         MessageDigest md5 = MessageDigest.getInstance("MD5");
         return md5.digest(data);
     }

     /**
      * Restore account sync settings from the given data input stream.
      */
     @Override
     public void restoreEntity(BackupDataInputStream data) {
         byte[] dataBytes = new byte[data.size()];
         try {
             // Read the data and convert it to a String.
             data.read(dataBytes);
             String dataString = new String(dataBytes, JSON_FORMAT_ENCODING);

             // Convert data to a JSON object.
             JSONObject dataJSON = new JSONObject(dataString);
             boolean masterSyncEnabled = dataJSON.getBoolean(KEY_MASTER_SYNC_ENABLED);
             JSONArray accountJSONArray = dataJSON.getJSONArray(KEY_ACCOUNTS);

             boolean currentMasterSyncEnabled = ContentResolver.getMasterSyncAutomatically();
             if (currentMasterSyncEnabled) {
                 // Disable master sync to prevent any syncs from running.
                 ContentResolver.setMasterSyncAutomatically(false);
             }

             try {
                 HashSet<Account> currentAccounts = getAccountsHashSet();
                 for (int i = 0; i < accountJSONArray.length(); i++) {
                     JSONObject accountJSON = (JSONObject) accountJSONArray.get(i);
                     String accountName = accountJSON.getString(KEY_ACCOUNT_NAME);
                     String accountType = accountJSON.getString(KEY_ACCOUNT_TYPE);

                     Account account = new Account(accountName, accountType);

                     // Check if the account already exists. Accounts that don't exist on the device
                     // yet won't be restored.
                     if (currentAccounts.contains(account)) {
                         restoreExistingAccountSyncSettingsFromJSON(accountJSON);
                     }
                 }
             } finally {
                 // Set the master sync preference to the value from the backup set.
                 ContentResolver.setMasterSyncAutomatically(masterSyncEnabled);
             }

             Log.i(TAG, "Restore successful.");
         } catch (IOException | JSONException e) {
             Log.e(TAG, "Couldn't restore account sync settings\n" + e);
         }
     }

     /**
      * Helper method - fetch accounts and return them as a HashSet.
      *
      * @return Accounts in a HashSet.
      */
     private HashSet<Account> getAccountsHashSet() {
         Account[] accounts = mAccountManager.getAccounts();
         HashSet<Account> accountHashSet = new HashSet<Account>();
         for (Account account : accounts) {
             accountHashSet.add(account);
         }
         return accountHashSet;
     }

     /**
      * Restore account sync settings using the given JSON. This function won't work if the account
      * doesn't exist yet.
      */
     private void restoreExistingAccountSyncSettingsFromJSON(JSONObject accountJSON)
             throws JSONException {
         // Restore authorities.
         JSONArray authorities = accountJSON.getJSONArray(KEY_ACCOUNT_AUTHORITIES);
         String accountName = accountJSON.getString(KEY_ACCOUNT_NAME);
         String accountType = accountJSON.getString(KEY_ACCOUNT_TYPE);
         final Account account = new Account(accountName, accountType);
         for (int i = 0; i < authorities.length(); i++) {
             JSONObject authority = (JSONObject) authorities.get(i);
             final String authorityName = authority.getString(KEY_AUTHORITY_NAME);
             boolean syncEnabled = authority.getBoolean(KEY_AUTHORITY_SYNC_ENABLED);

             // Cancel any active syncs.
             if (ContentResolver.isSyncActive(account, authorityName)) {
                 ContentResolver.cancelSync(account, authorityName);
             }

             boolean overwriteSync = true;
             Bundle initializationExtras = createSyncInitializationBundle();
             int currentSyncState = ContentResolver.getIsSyncable(account, authorityName);
             if (currentSyncState < 0) {
                 // Requesting a sync is an asynchronous operation, so we setup a countdown latch to
                 // wait for it to finish. Initialization syncs are generally very brief and
                 // shouldn't take too much time to finish.
                 final CountDownLatch latch = new CountDownLatch(1);
                 Object syncStatusObserverHandle = ContentResolver.addStatusChangeListener(
                         ContentResolver.SYNC_OBSERVER_TYPE_ACTIVE, new SyncStatusObserver() {
                             @Override
                             public void onStatusChanged(int which) {
                                 if (!ContentResolver.isSyncActive(account, authorityName)) {
                                     latch.countDown();
                                 }
                             }
                         });

                 // If we set sync settings for a sync that hasn't been initialized yet, we run the
                 // risk of having our changes overwritten later on when the sync gets initialized.
                 // To prevent this from happening we will manually initiate the sync adapter. We
                 // also explicitly pass in a Bundle with SYNC_EXTRAS_INITIALIZE to prevent a data
                 // sync from running after the initialization sync. Two syncs will be scheduled, but
                 // the second one (data sync) will override the first one (initialization sync) and
                 // still behave as an initialization sync because of the Bundle.
                 ContentResolver.requestSync(account, authorityName, initializationExtras);

                 boolean done = false;
                 try {
                     done = latch.await(SYNC_REQUEST_LATCH_TIMEOUT_SECONDS, TimeUnit.SECONDS);
                 } catch (InterruptedException e) {
                     Log.e(TAG, "CountDownLatch interrupted\n" + e);
                     done = false;
                 }
                 if (!done) {
                     overwriteSync = false;
                     Log.i(TAG, "CountDownLatch timed out, skipping '" + authorityName
                             + "' authority.");
                 }
                 ContentResolver.removeStatusChangeListener(syncStatusObserverHandle);
             }

             if (overwriteSync) {
                 ContentResolver.setSyncAutomatically(account, authorityName, syncEnabled);
                 Log.i(TAG, "Set sync automatically for '" + authorityName + "': " + syncEnabled);
             }
         }
     }

     private Bundle createSyncInitializationBundle() {
         Bundle extras = new Bundle();
         extras.putBoolean(ContentResolver.SYNC_EXTRAS_INITIALIZE, true);
         return extras;
     }

     @Override
     public void writeNewStateDescription(ParcelFileDescriptor newState) {

     }
 }
	/*
	* Copyright (C) 2014 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 org.json.JSONArray;
	import org.json.JSONException;
	import org.json.JSONObject;

	import android.accounts.Account;
	import android.accounts.AccountManager;
	import android.app.backup.BackupDataInputStream;
	import android.app.backup.BackupDataOutput;
	import android.app.backup.BackupHelper;
	import android.content.ContentResolver;
	import android.content.Context;
	import android.content.SyncAdapterType;
	import android.content.SyncStatusObserver;
	import android.os.Bundle;
	import android.os.ParcelFileDescriptor;
	import android.util.Log;

	import java.io.BufferedOutputStream;
	import java.io.DataInputStream;
	import java.io.DataOutputStream;
	import java.io.EOFException;
	import java.io.FileInputStream;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.security.MessageDigest;
	import java.security.NoSuchAlgorithmException;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.List;
	import java.util.concurrent.CountDownLatch;
	import java.util.concurrent.TimeUnit;

	/**
	* Helper for backing up account sync settings (whether or not a service should be synced). The
	* sync settings are backed up as a JSON object containing all the necessary information for
	* restoring the sync settings later.
	*/
	public class AccountSyncSettingsBackupHelper implements BackupHelper {

	private static final String TAG = "AccountSyncSettingsBackupHelper";
	private static final boolean DEBUG = false;

	private static final int STATE_VERSION = 1;
	private static final int MD5_BYTE_SIZE = 16;
	private static final int SYNC_REQUEST_LATCH_TIMEOUT_SECONDS = 1;

	private static final String JSON_FORMAT_HEADER_KEY = "account_data";
	private static final String JSON_FORMAT_ENCODING = "UTF-8";
	private static final int JSON_FORMAT_VERSION = 1;

	private static final String KEY_VERSION = "version";
	private static final String KEY_MASTER_SYNC_ENABLED = "masterSyncEnabled";
	private static final String KEY_ACCOUNTS = "accounts";
	private static final String KEY_ACCOUNT_NAME = "name";
	private static final String KEY_ACCOUNT_TYPE = "type";
	private static final String KEY_ACCOUNT_AUTHORITIES = "authorities";
	private static final String KEY_AUTHORITY_NAME = "name";
	private static final String KEY_AUTHORITY_SYNC_STATE = "syncState";
	private static final String KEY_AUTHORITY_SYNC_ENABLED = "syncEnabled";

	private Context mContext;
	private AccountManager mAccountManager;

	public AccountSyncSettingsBackupHelper(Context context) {
	mContext = context;
	mAccountManager = AccountManager.get(mContext);
	}

	/**
	* Take a snapshot of the current account sync settings and write them to the given output.
	*/
	@Override
	public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput output,
	ParcelFileDescriptor newState) {
	try {
	JSONObject dataJSON = serializeAccountSyncSettingsToJSON();

	if (DEBUG) {
	Log.d(TAG, "Account sync settings JSON: " + dataJSON);
	}

	// Encode JSON data to bytes.
	byte[] dataBytes = dataJSON.toString().getBytes(JSON_FORMAT_ENCODING);
	byte[] oldMd5Checksum = readOldMd5Checksum(oldState);
	byte[] newMd5Checksum = generateMd5Checksum(dataBytes);
	if (!Arrays.equals(oldMd5Checksum, newMd5Checksum)) {
	int dataSize = dataBytes.length;
	output.writeEntityHeader(JSON_FORMAT_HEADER_KEY, dataSize);
	output.writeEntityData(dataBytes, dataSize);

	Log.i(TAG, "Backup successful.");
	} else {
	Log.i(TAG, "Old and new MD5 checksums match. Skipping backup.");
	}

	writeNewMd5Checksum(newState, newMd5Checksum);
	} catch (JSONException \| IOException \| NoSuchAlgorithmException e) {
	Log.e(TAG, "Couldn't backup account sync settings\n" + e);
	}
	}

	/**
	* Fetch and serialize Account and authority information as a JSON Array.
	*/
	private JSONObject serializeAccountSyncSettingsToJSON() throws JSONException {
	Account[] accounts = mAccountManager.getAccounts();
	SyncAdapterType[] syncAdapters = ContentResolver.getSyncAdapterTypesAsUser(
	mContext.getUserId());

	// Create a map of Account types to authorities. Later this will make it easier for us to
	// generate our JSON.
	HashMap<String, List<String>> accountTypeToAuthorities = new HashMap<String,
	List<String>>();
	for (SyncAdapterType syncAdapter : syncAdapters) {
	// Skip adapters that aren’t visible to the user.
	if (!syncAdapter.isUserVisible()) {
	continue;
	}
	if (!accountTypeToAuthorities.containsKey(syncAdapter.accountType)) {
	accountTypeToAuthorities.put(syncAdapter.accountType, new ArrayList<String>());
	}
	accountTypeToAuthorities.get(syncAdapter.accountType).add(syncAdapter.authority);
	}

	// Generate JSON.
	JSONObject backupJSON = new JSONObject();
	backupJSON.put(KEY_VERSION, JSON_FORMAT_VERSION);
	backupJSON.put(KEY_MASTER_SYNC_ENABLED, ContentResolver.getMasterSyncAutomatically());

	JSONArray accountJSONArray = new JSONArray();
	for (Account account : accounts) {
	List<String> authorities = accountTypeToAuthorities.get(account.type);

	// We ignore Accounts that don't have any authorities because there would be no sync
	// settings for us to restore.
	if (authorities == null \|\| authorities.isEmpty()) {
	continue;
	}

	JSONObject accountJSON = new JSONObject();
	accountJSON.put(KEY_ACCOUNT_NAME, account.name);
	accountJSON.put(KEY_ACCOUNT_TYPE, account.type);

	// Add authorities for this Account type and check whether or not sync is enabled.
	JSONArray authoritiesJSONArray = new JSONArray();
	for (String authority : authorities) {
	int syncState = ContentResolver.getIsSyncable(account, authority);
	boolean syncEnabled = ContentResolver.getSyncAutomatically(account, authority);

	JSONObject authorityJSON = new JSONObject();
	authorityJSON.put(KEY_AUTHORITY_NAME, authority);
	authorityJSON.put(KEY_AUTHORITY_SYNC_STATE, syncState);
	authorityJSON.put(KEY_AUTHORITY_SYNC_ENABLED, syncEnabled);
	authoritiesJSONArray.put(authorityJSON);
	}
	accountJSON.put(KEY_ACCOUNT_AUTHORITIES, authoritiesJSONArray);

	accountJSONArray.put(accountJSON);
	}
	backupJSON.put(KEY_ACCOUNTS, accountJSONArray);

	return backupJSON;
	}

	/**
	* Read the MD5 checksum from the old state.
	*
	* @return the old MD5 checksum
	*/
	private byte[] readOldMd5Checksum(ParcelFileDescriptor oldState) throws IOException {
	DataInputStream dataInput = new DataInputStream(
	new FileInputStream(oldState.getFileDescriptor()));

	byte[] oldMd5Checksum = new byte[MD5_BYTE_SIZE];
	try {
	int stateVersion = dataInput.readInt();
	if (stateVersion <= STATE_VERSION) {
	// If the state version is a version we can understand then read the MD5 sum,
	// otherwise we return an empty byte array for the MD5 sum which will force a
	// backup.
	for (int i = 0; i < MD5_BYTE_SIZE; i++) {
	oldMd5Checksum[i] = dataInput.readByte();
	}
	} else {
	Log.i(TAG, "Backup state version is: " + stateVersion
	+ " (support only up to version " + STATE_VERSION + ")");
	}
	} catch (EOFException eof) {
	// Initial state may be empty.
	} finally {
	dataInput.close();
	}
	return oldMd5Checksum;
	}

	/**
	* Write the given checksum to the file descriptor.
	*/
	private void writeNewMd5Checksum(ParcelFileDescriptor newState, byte[] md5Checksum)
	throws IOException {
	DataOutputStream dataOutput = new DataOutputStream(
	new BufferedOutputStream(new FileOutputStream(newState.getFileDescriptor())));

	dataOutput.writeInt(STATE_VERSION);
	dataOutput.write(md5Checksum);
	dataOutput.close();
	}

	private byte[] generateMd5Checksum(byte[] data) throws NoSuchAlgorithmException {
	if (data == null) {
	return null;
	}

	MessageDigest md5 = MessageDigest.getInstance("MD5");
	return md5.digest(data);
	}

	/**
	* Restore account sync settings from the given data input stream.
	*/
	@Override
	public void restoreEntity(BackupDataInputStream data) {
	byte[] dataBytes = new byte[data.size()];
	try {
	// Read the data and convert it to a String.
	data.read(dataBytes);
	String dataString = new String(dataBytes, JSON_FORMAT_ENCODING);

	// Convert data to a JSON object.
	JSONObject dataJSON = new JSONObject(dataString);
	boolean masterSyncEnabled = dataJSON.getBoolean(KEY_MASTER_SYNC_ENABLED);
	JSONArray accountJSONArray = dataJSON.getJSONArray(KEY_ACCOUNTS);

	boolean currentMasterSyncEnabled = ContentResolver.getMasterSyncAutomatically();
	if (currentMasterSyncEnabled) {
	// Disable master sync to prevent any syncs from running.
	ContentResolver.setMasterSyncAutomatically(false);
	}

	try {
	HashSet<Account> currentAccounts = getAccountsHashSet();
	for (int i = 0; i < accountJSONArray.length(); i++) {
	JSONObject accountJSON = (JSONObject) accountJSONArray.get(i);
	String accountName = accountJSON.getString(KEY_ACCOUNT_NAME);
	String accountType = accountJSON.getString(KEY_ACCOUNT_TYPE);

	Account account = new Account(accountName, accountType);

	// Check if the account already exists. Accounts that don't exist on the device
	// yet won't be restored.
	if (currentAccounts.contains(account)) {
	restoreExistingAccountSyncSettingsFromJSON(accountJSON);
	}
	}
	} finally {
	// Set the master sync preference to the value from the backup set.
	ContentResolver.setMasterSyncAutomatically(masterSyncEnabled);
	}

	Log.i(TAG, "Restore successful.");
	} catch (IOException \| JSONException e) {
	Log.e(TAG, "Couldn't restore account sync settings\n" + e);
	}
	}

	/**
	* Helper method - fetch accounts and return them as a HashSet.
	*
	* @return Accounts in a HashSet.
	*/
	private HashSet<Account> getAccountsHashSet() {
	Account[] accounts = mAccountManager.getAccounts();
	HashSet<Account> accountHashSet = new HashSet<Account>();
	for (Account account : accounts) {
	accountHashSet.add(account);
	}
	return accountHashSet;
	}

	/**
	* Restore account sync settings using the given JSON. This function won't work if the account
	* doesn't exist yet.
	*/
	private void restoreExistingAccountSyncSettingsFromJSON(JSONObject accountJSON)
	throws JSONException {
	// Restore authorities.
	JSONArray authorities = accountJSON.getJSONArray(KEY_ACCOUNT_AUTHORITIES);
	String accountName = accountJSON.getString(KEY_ACCOUNT_NAME);
	String accountType = accountJSON.getString(KEY_ACCOUNT_TYPE);
	final Account account = new Account(accountName, accountType);
	for (int i = 0; i < authorities.length(); i++) {
	JSONObject authority = (JSONObject) authorities.get(i);
	final String authorityName = authority.getString(KEY_AUTHORITY_NAME);
	boolean syncEnabled = authority.getBoolean(KEY_AUTHORITY_SYNC_ENABLED);

	// Cancel any active syncs.
	if (ContentResolver.isSyncActive(account, authorityName)) {
	ContentResolver.cancelSync(account, authorityName);
	}

	boolean overwriteSync = true;
	Bundle initializationExtras = createSyncInitializationBundle();
	int currentSyncState = ContentResolver.getIsSyncable(account, authorityName);
	if (currentSyncState < 0) {
	// Requesting a sync is an asynchronous operation, so we setup a countdown latch to
	// wait for it to finish. Initialization syncs are generally very brief and
	// shouldn't take too much time to finish.
	final CountDownLatch latch = new CountDownLatch(1);
	Object syncStatusObserverHandle = ContentResolver.addStatusChangeListener(
	ContentResolver.SYNC_OBSERVER_TYPE_ACTIVE, new SyncStatusObserver() {
	@Override
	public void onStatusChanged(int which) {
	if (!ContentResolver.isSyncActive(account, authorityName)) {
	latch.countDown();
	}
	}
	});

	// If we set sync settings for a sync that hasn't been initialized yet, we run the
	// risk of having our changes overwritten later on when the sync gets initialized.
	// To prevent this from happening we will manually initiate the sync adapter. We
	// also explicitly pass in a Bundle with SYNC_EXTRAS_INITIALIZE to prevent a data
	// sync from running after the initialization sync. Two syncs will be scheduled, but
	// the second one (data sync) will override the first one (initialization sync) and
	// still behave as an initialization sync because of the Bundle.
	ContentResolver.requestSync(account, authorityName, initializationExtras);

	boolean done = false;
	try {
	done = latch.await(SYNC_REQUEST_LATCH_TIMEOUT_SECONDS, TimeUnit.SECONDS);
	} catch (InterruptedException e) {
	Log.e(TAG, "CountDownLatch interrupted\n" + e);
	done = false;
	}
	if (!done) {
	overwriteSync = false;
	Log.i(TAG, "CountDownLatch timed out, skipping '" + authorityName
	+ "' authority.");
	}
	ContentResolver.removeStatusChangeListener(syncStatusObserverHandle);
	}

	if (overwriteSync) {
	ContentResolver.setSyncAutomatically(account, authorityName, syncEnabled);
	Log.i(TAG, "Set sync automatically for '" + authorityName + "': " + syncEnabled);
	}
	}
	}

	private Bundle createSyncInitializationBundle() {
	Bundle extras = new Bundle();
	extras.putBoolean(ContentResolver.SYNC_EXTRAS_INITIALIZE, true);
	return extras;
	}

	@Override
	public void writeNewStateDescription(ParcelFileDescriptor newState) {

	}
	}