A simple abstract class developers can use to detect changes to a directory (nonrecursively) and fire callbacks as a result.
Monitors files (using inotify) to fire an event after files are accessed or changed by any process on the device (including this one). FileObserver is an abstract class; subclasses must implement the event handler onEvent(int, String).
Full Documentation Link: http://developer.android.com/reference/android/os/FileObserver.html