FileObserver getting strange events

Question

Ok, this is simple: I have a FileObserver class to observe a folder with music. So I implemented onEvent and all that stuff, but when I move or paste a file on that folder using a file manager, instead of getting a FileObserver.MOVED_TO or a FileObserver.CREATE, I'm getting weird events with numbers like 1073741656, that are not documented on: http://developer.android.com/reference/android/os/FileObserver.html

So how do I get those specific events like deleting, moving, creating and pasting?

[edit] Here is the code:

 private class MusicsFileObserver extends FileObserver {

    public MusicsFileObserver(String root) {
        super(root);

        if (!root.endsWith(File.separator)) {
            root += File.separator;
        }
    }

    @SuppressWarnings("unused")
    public void close() {
        super.finalize();
    }

    public void onEvent(final int event, String path) {
      //here is the problem, if you see the documentation, when a file is moved 
      //to this directory, event should be equal to FileObserver.MOVED_TO, 
      //a constant value of 128. But when debugging, instead of entering here one time
      //with event == 128, this method onEvent is being called 4~5 times with event
      //with numbers like 1073741656
        if (event != FileObserver.ACCESS || event != FileObserver.OPEN || event != 32768)
            runOnUiThread(new Runnable() {
                public void run() {
                    rescanMusics();
                }
            });
    }
}

Can you post some of your code and annotate it with some comments about where the issue is happening? — nicholas.hauschild, Jun 13 '11 at 21:23
Are you in the directory you think you are in? The if check in your Constructor isn't doing anything currently. If you have no File.spearator at the end of your root String passed in, it will remain that way, meaning it is looking for a file and not a directory... — nicholas.hauschild, Jun 14 '11 at 13:18
Hmm, now that you said, I'm moving a file to a subfolder of the directory I'm observing.. I'll test what event I get when I paste it on the directory itself — Paulo Cesar, Jun 14 '11 at 13:39
Found a way that works. Instead of checking the int "event", I'm checking the string path, because when somebody removes, copies, moves, and mess with a file, it always returns the path of the file — Paulo Cesar, Jun 14 '11 at 13:50

mvsjes2 · Answer 1 · 2021-07-19T18:43:13.827

14

For anyone else that runs into this, I found the MOVED_TO and MOVED_FROM events have high-order bits turned on in the event flag. MOVED_FROM is 0x40000040 and MOVED_TO is 0x40000080. The workaround is to simply 'and' ALL_EVENTS with the event code to turn off the high bits, i.e. "event &= FileObserver.ALL_EVENTS"

Update: I found the inotify flags that you can get from https://asyncinotify.readthedocs.io/en/latest/doc/asyncinotify.html, it would be nice if google added these bit flags to the FileObserver doc.

edited Jul 19 '21 at 18:43

answered May 04 '12 at 20:08

mvsjes2

1,254
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Is this true of all events or just MOVED_TO and MOVED_FROM? – robross0606 Jun 29 '18 at 19:51
The link you provided is dead. This comment is long 'cos... SO. – vesperto May 31 '21 at 16:16

score 5 · Answer 2 · answered Jun 19 '12 at 15:37

Observer event type like this:

public void onEvent(int event) {
      if ((FileObserver.CREATE & event)!=0) {
        // do what ever you want.
      } else if ((FileObserver.MODIFY & event)!=0) {
        // do what ever you want.           
      } ...... etc
}

score 1 · Answer 3 · edited Jun 20 '20 at 09:12

1

If anyone else comes here from Google, be aware of this from the documentation:

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.

edited Jun 20 '20 at 09:12

Community

1
1

answered Jul 28 '17 at 14:42

Jon McClung

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Thanks. This helped, but it does rather beg the question as to how one monitors for the creation of a specific file... when CREATE is one of the event types permitted as an argument.. – ejoftheweb May 02 '19 at 18:54

score 0 · Answer 4 · answered Jun 10 '14 at 15:44

Try to link reference to Observer in your Application class. like this

private ArrayList<FileObserver> mObservers = new ArrayList<FileObserver>();

public void addObserver(FileObserver observer){
    mObservers.add(observer);
}

public void removeObserver(FileObserver observer){
    mObservers.remove(observer);
}

This works for me!

FileObserver getting strange events

4 Answers4

startWatching()