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FileObserver.javaAPI DocAndroid 5.1 API8103Thu Mar 12 22:22:10 GMT 2015android.os

FileObserver

public abstract class FileObserver extends Object
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 {@link #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.

Fields Summary
public static final int
ACCESS
Event type: Data was read from a file
public static final int
MODIFY
Event type: Data was written to a file
public static final int
ATTRIB
Event type: Metadata (permissions, owner, timestamp) was changed explicitly
public static final int
CLOSE_WRITE
Event type: Someone had a file or directory open for writing, and closed it
public static final int
CLOSE_NOWRITE
Event type: Someone had a file or directory open read-only, and closed it
public static final int
OPEN
Event type: A file or directory was opened
public static final int
MOVED_FROM
Event type: A file or subdirectory was moved from the monitored directory
public static final int
MOVED_TO
Event type: A file or subdirectory was moved to the monitored directory
public static final int
CREATE
Event type: A new file or subdirectory was created under the monitored directory
public static final int
DELETE
Event type: A file was deleted from the monitored directory
public static final int
DELETE_SELF
Event type: The monitored file or directory was deleted; monitoring effectively stops
public static final int
MOVE_SELF
Event type: The monitored file or directory was moved; monitoring continues
public static final int
ALL_EVENTS
Event mask: All valid event types, combined
private static final String
LOG_TAG
private static ObserverThread
s_observerThread
private String
m_path
private Integer
m_descriptor
private int
m_mask
Constructors Summary
public FileObserver(String path)
Equivalent to FileObserver(path, FileObserver.ALL_EVENTS).

        this(path, ALL_EVENTS);
public 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 {@link #startWatching()} before you will receive events.

param
path The file or directory to monitor
param
mask The event or events (added together) to watch for

        m_path = path;
        m_mask = mask;
        m_descriptor = -1;
Methods Summary
protected voidfinalize()

        stopWatching();
public abstract voidonEvent(int event, java.lang.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 {@link Handler#post(Runnable)} to shift event handling work to the main thread to avoid concurrency problems.

Event handlers must not throw exceptions.

param
event The type of event which happened
param
path The path, relative to the main monitored file or directory, of the file or directory which triggered the event

public voidstartWatching()
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.
        if (m_descriptor < 0) {
            m_descriptor = s_observerThread.startWatching(m_path, m_mask, this);
        }
    
public voidstopWatching()
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.
        if (m_descriptor >= 0) {
            s_observerThread.stopWatching(m_descriptor);
            m_descriptor = -1;
        }