public
abstract
class
FileObserver
extends Object
| java.lang.Object | |
| ↳ | android.os.FileObserver |
Monitors files (using inotify)
to fire an event after files are accessed or changed by by any process on
the device (including this one). FileObserver is an abstract class;
subclasses must implement the event handler onEvent(int, String).
Each FileObserver instance monitors a single file or directory. If a directory is monitored, events will be triggered for all files and subdirectories inside the monitored directory.
An event mask is used to specify which changes or actions to report. Event type constants are used to describe the possible changes in the event mask as well as what actually happened in event callbacks.
Warning: If a FileObserver is garbage collected, it will stop sending events. To ensure you keep receiving events, you must keep a reference to the FileObserver instance from some other live object.
Constants | |
|---|---|
int |
ACCESS
Event type: Data was read from a file |
int |
ALL_EVENTS
Event mask: All valid event types, combined |
int |
ATTRIB
Event type: Metadata (permissions, owner, timestamp) was changed explicitly |
int |
CLOSE_NOWRITE
Event type: Someone had a file or directory open read-only, and closed it |
int |
CLOSE_WRITE
Event type: Someone had a file or directory open for writing, and closed it |
int |
CREATE
Event type: A new file or subdirectory was created under the monitored directory |
int |
DELETE
Event type: A file was deleted from the monitored directory |
int |
DELETE_SELF
Event type: The monitored file or directory was deleted; monitoring effectively stops |
int |
MODIFY
Event type: Data was written to a file |
int |
MOVED_FROM
Event type: A file or subdirectory was moved from the monitored directory |
int |
MOVED_TO
Event type: A file or subdirectory was moved to the monitored directory |
int |
MOVE_SELF
Event type: The monitored file or directory was moved; monitoring continues |
int |
OPEN
Event type: A file or directory was opened |
Public constructors | |
|---|---|
FileObserver(String path)
Equivalent to FileObserver(path, FileObserver.ALL_EVENTS). |
|
FileObserver(String path, int mask)
Create a new file observer for a certain file or directory. |
|
Public methods | |
|---|---|
abstract
void
|
onEvent(int event, String path)
The event handler, which must be implemented by subclasses. |
void
|
startWatching()
Start watching for events. |
void
|
stopWatching()
Stop watching for events. |
Protected methods | |
|---|---|
void
|
finalize()
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
int ACCESS
Event type: Data was read from a file
Constant Value: 1 (0x00000001)
int ALL_EVENTS
Event mask: All valid event types, combined
Constant Value: 4095 (0x00000fff)
int ATTRIB
Event type: Metadata (permissions, owner, timestamp) was changed explicitly
Constant Value: 4 (0x00000004)
int CLOSE_NOWRITE
Event type: Someone had a file or directory open read-only, and closed it
Constant Value: 16 (0x00000010)
int CLOSE_WRITE
Event type: Someone had a file or directory open for writing, and closed it
Constant Value: 8 (0x00000008)
int CREATE
Event type: A new file or subdirectory was created under the monitored directory
Constant Value: 256 (0x00000100)
int DELETE
Event type: A file was deleted from the monitored directory
Constant Value: 512 (0x00000200)
int DELETE_SELF
Event type: The monitored file or directory was deleted; monitoring effectively stops
Constant Value: 1024 (0x00000400)
int MODIFY
Event type: Data was written to a file
Constant Value: 2 (0x00000002)
int MOVED_FROM
Event type: A file or subdirectory was moved from the monitored directory
Constant Value: 64 (0x00000040)
int MOVED_TO
Event type: A file or subdirectory was moved to the monitored directory
Constant Value: 128 (0x00000080)
int MOVE_SELF
Event type: The monitored file or directory was moved; monitoring continues
Constant Value: 2048 (0x00000800)
int OPEN
Event type: A file or directory was opened
Constant Value: 32 (0x00000020)
FileObserver (String path)
Equivalent to FileObserver(path, FileObserver.ALL_EVENTS).
| Parameters | |
|---|---|
path |
String
|
FileObserver (String path, int mask)
Create a new file observer for a certain file or directory.
Monitoring does not start on creation! You must call
startWatching() before you will receive events.
| Parameters | |
|---|---|
path |
String:
The file or directory to monitor |
mask |
int:
The event or events (added together) to watch for
|
Developers
void onEvent (int event,
String path)
The event handler, which must be implemented by subclasses.
This method is invoked on a special FileObserver thread.
It runs independently of any threads, so take care to use appropriate
synchronization! Consider using post(Runnable) to shift
event handling work to the main thread to avoid concurrency problems.
Event handlers must not throw exceptions.
| Parameters | |
|---|---|
event |
int:
The type of event which happened |
path |
String:
The path, relative to the main monitored file or directory,
of the file or directory which triggered the event
|
void startWatching ()
Start watching for events. The monitored file or directory must exist at this time, or else no events will be reported (even if it appears later). If monitoring is already started, this call has no effect.
void stopWatching ()
Stop watching for events. Some events may be in process, so events may continue to be reported even after this method completes. If monitoring is already stopped, this call has no effect.
void finalize ()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
A subclass overrides the 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.