IBackupHelper.PerformBackup Method
Definition
Important
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Based on oldState, determine what application content
needs to be backed up, write it to data, and fill in
newState with the complete state as it exists now.
[Android.Runtime.Register("performBackup", "(Landroid/os/ParcelFileDescriptor;Landroid/app/backup/BackupDataOutput;Landroid/os/ParcelFileDescriptor;)V", "GetPerformBackup_Landroid_os_ParcelFileDescriptor_Landroid_app_backup_BackupDataOutput_Landroid_os_ParcelFileDescriptor_Handler:Android.App.Backup.IBackupHelperInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")]
public void PerformBackup (Android.OS.ParcelFileDescriptor? oldState, Android.App.Backup.BackupDataOutput? data, Android.OS.ParcelFileDescriptor? newState);[<Android.Runtime.Register("performBackup", "(Landroid/os/ParcelFileDescriptor;Landroid/app/backup/BackupDataOutput;Landroid/os/ParcelFileDescriptor;)V", "GetPerformBackup_Landroid_os_ParcelFileDescriptor_Landroid_app_backup_BackupDataOutput_Landroid_os_ParcelFileDescriptor_Handler:Android.App.Backup.IBackupHelperInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")>]
abstract member PerformBackup : Android.OS.ParcelFileDescriptor * Android.App.Backup.BackupDataOutput * Android.OS.ParcelFileDescriptor -> unitParameters
- 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.
- Attributes
Remarks
Based on oldState, determine what application content needs to be backed up, write it to data, and fill in newState with the complete state as it exists now.
Implementing this method is much like implementing BackupAgent#onBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor) onBackup() — the method parameters are the same. When this method is invoked the oldState descriptor points to the beginning of the state data written during this helper's previous backup operation, and the newState descriptor points to the file location at which the helper should write its new state after performing the backup operation. <p class="note"> <strong>Note:</strong> The helper should not close or seek either the oldState or the newState file descriptors. It is essential that when reading the helper's saved state from the oldState file, no extra content is consumed beyond what was stored by this helper. If more old state data is read, even accidentally, it will make it impossible for additional helpers that may be invoked after this one to properly reconstruct their prior state.
Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.