public class FileBackupHelper extends Object implements BackupHelper
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(android.content.Context, java.lang.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.
Constructor and Description |
---|
FileBackupHelper(Context context,
String... files)
Construct a helper to manage backup/restore of entire files within the
application's data directory hierarchy.
|
Modifier and Type | Method and Description |
---|---|
protected void |
finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
|
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) |
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
writeNewStateDescription
public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState)
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.
performBackup
in interface BackupHelper
oldState
- 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
- 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
- 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.public void restoreEntity(BackupDataInputStream data)
This should only be called directly from within the BackupAgentHelper
implementation.
restoreEntity
in interface BackupHelper
data
- An open BackupDataInputStream
from which the backup data can be read.protected void finalize() throws Throwable
Object
finalize
method to dispose of
system resources or to perform other cleanup.
The general contract of finalize
is that it is invoked
if and when the JavaTM virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize
method may take any action, including
making this object available again to other threads; the usual purpose
of finalize
, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize
method of class Object
performs no
special action; it simply returns normally. Subclasses of
Object
may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize
method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize
method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize
method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize
method causes
the finalization of this object to be halted, but is otherwise
ignored.
public void writeNewStateDescription(ParcelFileDescriptor fd)