FileBackupHelper

Kotlin |Java

public class FileBackupHelper
extends Object implements BackupHelper

java.lang.Object
↳	android.app.backup.FileBackupHelper

A helper class that can be used in conjunction with BackupAgentHelper to manage the backup of a set of files. Whenever backup is performed, all files changed since the last backup will be saved in their entirety. When backup first occurs, every file in the list provided to FileBackupHelper(Context, String) will be backed up.

During restore, if the helper encounters data for a file that was not specified when the FileBackupHelper object was constructed, that data will be ignored.

Note: This should be used only with small configuration files, not large binary files.

Summary

Public constructors
`FileBackupHelper(Context context, String... files)` Construct a helper to manage backup/restore of entire files within the application's data directory hierarchy.

Public methods
`void`	`performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState)` Based on `oldState`, determine which of the files from the application's data directory need to be backed up, write them to the data stream, and fill in `newState` with the state as it exists now.
`void`	`restoreEntity(BackupDataInputStream data)` Restore one record [representing a single file] from the restore dataset.
`void`	`writeNewStateDescription(ParcelFileDescriptor fd)` Called by `BackupAgentHelper` after a restore operation to write the backup state file corresponding to the data as processed by the helper.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          android.app.backup.BackupHelper

`abstract void`	`performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState)` 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.
`abstract void`	`restoreEntity(BackupDataInputStream data)` Called by `BackupAgentHelper` to restore a single entity from the restore data set.
`abstract void`	`writeNewStateDescription(ParcelFileDescriptor newState)` Called by `BackupAgentHelper` after a restore operation to write the backup state file corresponding to the data as processed by the helper.

Public constructors

FileBackupHelper

Added in API level 8

public FileBackupHelper (Context context, 
                String... files)

Construct a helper to manage backup/restore of entire files within the application's data directory hierarchy.

Parameters
`context`	`Context`: The backup agent's Context object
`files`	`String`: A list of the files to be backed up or restored.

Public methods

performBackup

Added in API level 8

public void performBackup (ParcelFileDescriptor oldState, 
                BackupDataOutput data, 
                ParcelFileDescriptor newState)

Based on oldState, determine which of the files from the application's data directory need to be backed up, write them to the data stream, and fill in newState with the state as it exists now. When oldState is null, all the files will be backed up.

This should only be called directly from within the BackupAgentHelper implementation. See BackupAgent.onBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor) for a description of parameter meanings.

Parameters
`oldState`	`ParcelFileDescriptor`: An open, read-only `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 `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

public void restoreEntity (BackupDataInputStream data)

Restore one record [representing a single file] from the restore dataset.

This should only be called directly from within the BackupAgentHelper implementation.

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

writeNewStateDescription

Added in API level 8

public void writeNewStateDescription (ParcelFileDescriptor fd)

Called by BackupAgentHelper after a restore operation to write the backup state file corresponding to the data as processed by the helper. The data written here will be available to the helper during the next call to its performBackup() method.

This method will be called even if the handler's restoreEntity() method was never invoked during the restore operation.

Note: The helper should not close or seek the newState file descriptor.

Parameters
`fd`	`ParcelFileDescriptor`: A `ParcelFileDescriptor` to which the new state will be written.