Как реализовать FileObserver на java в Android?

Пробую создать простой FileObserver. Сервис запускается и работает, но события не приходят. Разрешение READ_EXTERNAL_STORAGE есть.

public class MyService extends Service {
public MyService() {
}

public static FileObserver observer;

@Override
public int onStartCommand(Intent intent, int flags, int startId) {

    final String pathToWatch = android.os.Environment.getExternalStorageDirectory().toString() + "/DCIM/Camera/";
    File file = new File(pathToWatch);
    Log.i("MyService", "My Service Started and trying to watch " + pathToWatch);

    observer = new FileObserver(file,FileObserver.ALL_EVENTS) { 
        @Override
        public void onEvent(int event, String file) {
            Log.i("MyService", "File created");
        }
    };
    observer.startWatching();
    return Service.START_STICKY;
}

@Override
public void onCreate() {
    super.onCreate();
}

@Override
public IBinder onBind(Intent intent) {
    //TODO for communication return IBinder implementation
    return null;
}

запускаю вот так

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
        ActivityCompat.requestPermissions(MainActivity.this,
                new String[]{
                        Manifest.permission.READ_EXTERNAL_STORAGE,
                },
                1);
    } else {

        Intent intent = new Intent(this, MyService.class);
        this.startService(intent);
    }
}