FileObserver doesn't work

Question

In my Android app I want to detect events from directory. Here is code:

String path = Environment.getExternalStorageDirectory()
            + File.separator + "test2";
    Log.d("test", "path is " + path);

    FileObserver fileObserver = new FileObserver(path, FileObserver.ALL_EVENTS) {
        @Override
        public void onEvent(int event, String path) {
            Log.d("test", "event dectect " + event + " " + path);
        }
    };

    fileObserver.startWatching();

I copy new file to the directory. But I don't get any event. Please show me where I made a mistake.

probably Activity is in Pause or Stop state when copying new file in directory. so try it by copying file in directory from `adb shell` without minimizing Activity — ρяσѕρєя K, Sep 05 '15 at 05:00
I copied the new file using wife transfer ( I uploaded it from my computer). So I don't think the Activity is in Pause or Stop. — TOP, Sep 05 '15 at 05:06

score 18 · Accepted Answer · answered Sep 05 '15 at 05:10

You cannot use a local variable to store your FileObserver, it would be available for garbage collection after the method is run.

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.

Solution: save it to a field.

score 1 · Answer 2 · answered May 31 '18 at 12:31

1

Adding storage permission worked for me.

answered May 31 '18 at 12:31

user3219477

134
3
10

score 0 · Answer 3 · answered May 31 '16 at 21:16

It seems that FileObserver does not work on symbolic links, which is what is returned by Environment.getExternalStorage().

The trick for me was to resolve the links using File.getCanonicalPath()

Example:

File file = new File(Environment.getExteranlStorage(), "myfile");
new FileObserver(file.getCanonicalPath()) ...

score 0 · Answer 4 · answered Oct 11 '21 at 15:49

0

Expanding on @user3219477's answer be sure to go in to Settings->Apps->YourApp and grant Storage permission if you aren't requesting it dynamically in your app.

answered Oct 11 '21 at 15:49

Lucy

436
5
8

FileObserver doesn't work

4 Answers4

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