Added in API level 8

SharedPreferencesBackupHelper


open class SharedPreferencesBackupHelper : BackupHelper
kotlin.Any
   ↳ android.app.backup.SharedPreferencesBackupHelper

A helper class that can be used in conjunction with android.app.backup.BackupAgentHelper to manage the backup of android.content.SharedPreferences. Whenever a backup is performed, it will back up all named shared preferences that have changed since the last backup operation.

To use this class, the application's backup agent class should extend android.app.backup.BackupAgentHelper. Then, in the agent's BackupAgent#onCreate() method, an instance of this class should be allocated and installed as a backup/restore handler within the BackupAgentHelper framework. For example, an agent supporting backup and restore for an application with two groups of android.content.SharedPreferences data might look something like this:

import android.app.backup.BackupAgentHelper;
  import android.app.backup.SharedPreferencesBackupHelper;
 
  public class MyBackupAgent extends BackupAgentHelper {
      // The names of the SharedPreferences groups that the application maintains.  These
      // are the same strings that are passed to <code><a docref="android.content.Context$getSharedPreferences(kotlin.String, kotlin.Int)">Context#getSharedPreferences(String, int)</a></code>.
      static final String PREFS_DISPLAY = "displayprefs";
      static final String PREFS_SCORES = "highscores";
 
      // An arbitrary string used within the BackupAgentHelper implementation to
      // identify the SharedPreferenceBackupHelper's data.
      static final String MY_PREFS_BACKUP_KEY = "myprefs";
 
      // Allocate a helper and install it.
      public void onCreate() {
          SharedPreferencesBackupHelper helper =
                  new SharedPreferencesBackupHelper(this, PREFS_DISPLAY, PREFS_SCORES);
          addHelper(MY_PREFS_BACKUP_KEY, helper);
      }
  }

No further implementation is needed; the BackupAgentHelper mechanism automatically dispatches the BackupAgent.onBackup() and BackupAgent.onRestore() callbacks to the SharedPreferencesBackupHelper as appropriate.

Summary

Public constructors
SharedPreferencesBackupHelper(context: Context!, vararg prefGroups: String!)

Construct a helper for backing up and restoring the android.content.SharedPreferences under the given names.

Public methods
open Unit

Backs up the configured android.content.SharedPreferences groups.

open Unit

Restores one entity from the restore data stream to its proper shared preferences file store.

open Unit

Public constructors

SharedPreferencesBackupHelper

Added in API level 8
SharedPreferencesBackupHelper(
    context: Context!,
    vararg prefGroups: String!)

Construct a helper for backing up and restoring the android.content.SharedPreferences under the given names.

Parameters
context Context!: The application android.content.Context
prefGroups String!: The names of each android.content.SharedPreferences file to back up

Public methods

performBackup

Added in API level 8
open fun performBackup(
    oldState: ParcelFileDescriptor!,
    data: BackupDataOutput!,
    newState: ParcelFileDescriptor!
): Unit

Backs up the configured android.content.SharedPreferences groups.

Parameters
oldState ParcelFileDescriptor!: An open, read-only android.os.ParcelFileDescriptor pointing to the last backup state provided by the application. May be null, in which case no prior state is being provided and the application should perform a full backup.
data BackupDataOutput!: An open, read/write BackupDataOutput pointing to the backup data destination. Typically the application will use backup helper classes to write to this file.
newState ParcelFileDescriptor!: An open, read/write android.os.ParcelFileDescriptor pointing to an empty file. The application should record the final backup state here after writing the requested data to the data output stream.

restoreEntity

Added in API level 8
open fun restoreEntity(data: BackupDataInputStream!): Unit

Restores one entity from the restore data stream to its proper shared preferences file store.

Parameters
data BackupDataInputStream!: An open BackupDataInputStream from which the backup data can be read.

writeNewStateDescription

Added in API level 8
open fun writeNewStateDescription(fd: ParcelFileDescriptor!): Unit
Parameters
newState A android.os.ParcelFileDescriptor to which the new state will be written.