File observer stops working after some time

Question

I want to listen to the changes occured in file system.I am using FileObserver.Here is my code:

Code:

class MyDirObserver extends FileObserver {
    String superPath;
    public MyDirObserver(String path) {
        super(path, ALL_EVENTS);
        this.superPath = path;
    }


    public void onEvent(int event, String path) {
        Log.e("onEvent of Directory", "=== onEvent ===");
        try {
            _Dump("dir", event, path, superPath);
        } catch (NullPointerException ex) {
            Log.e("ERROR", "I am getting error");
        }
    }
}


private void _Dump(final String tag, int event, String path, String superPath) {
    Log.d(tag, "=== dump begin ===");
    Log.d(tag, "path=" + path);
    Log.d(tag, "super path=" + superPath);
    Log.d(tag, "event list:");
    if ((event & FileObserver.OPEN) != 0) {
        Log.d(tag, "  OPEN");
    }
    if ((event & FileObserver.CLOSE_NOWRITE) != 0) {
        Log.d(tag, "  CLOSE_NOWRITE");
    }
    if ((event & FileObserver.CLOSE_WRITE) != 0) {


        Log.d(tag, "  CLOSE_WRITE");
        Log.i("NEWFILEOBSERVER", "File is Modified");
        if (path != null) {
            Log.d("---------FilePath", superPath + path);
        }


    }
    if ((event & FileObserver.CREATE) != 0) {
        isCreate = true;
        Log.i("NEWFILEOBSERVER", "File is Created ");
        if (path != null) {
            Log.d("---------FilePath", superPath + path);
        }
        Log.d(tag, "  CREATE");


    }
    if ((event & FileObserver.DELETE) != 0) {
        Log.i("NEWFILEOBSERVER", "File is deleted");
        if (path != null) {
            Log.d("---------FilePath", superPath + path);
        }
        //  startMyActivity("A new file is deleted thats="+superPath); 


        Log.d(tag, "  DELETE");


    }

    if ((event & FileObserver.DELETE_SELF) != 0) {
        Log.d(tag, "  DELETE_SELF");
    }

    if ((event & FileObserver.ACCESS) != 0) {
        Log.d(tag, "  ACCESS");
    }

    if ((event & FileObserver.MODIFY) != 0) {
        if (!isModified)
            isModified = true;

        if (isModified && isOpen)
            isAgainModified = true;
        Log.d(tag, "  MODIFY");
    }

    if ((event & FileObserver.MOVED_FROM) != 0) {
        Log.d(tag, "  MOVED_FROM");
        if (path != null) {
            Log.d("---------FilePath", superPath + path);
        }
    }

    if ((event & FileObserver.MOVED_TO) != 0) {
        Log.d(tag, "  MOVED_TO");
        if (path != null) {
            Log.d("---------FilePath", superPath + path);
        }
    }

    if ((event & FileObserver.MOVE_SELF) != 0) {
        Log.d(tag, "  MOVE_SELF");
    }

    if ((event & FileObserver.ATTRIB) != 0) {
        Log.d(tag, "  ATTRIB");
    }

    Log.d(tag, "=== dump end ===");
}

it stops after some time.I dont get the exact time but doesnt work always though I call startWatching() in service in a loop which runs for all the folders of sdcard and calls startWatching() for each of them. It shows unpredictable behaviour and stops listening for some folders and runs perfectly for the others.

I hope you guys help me. I tried many ways but it doesn't work perfectly. Am I doing something wrong? Or is there some other way to do this.

Answer 1

http://developer.android.com/reference/android/os/FileObserver.html

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.

Answer 2

Declare FileObserver as Static and global which will retain the instance of Fileobserver and restrict OS to take service into garbage collector.