Recovery database

I appreciate your help Mr. James. On the first read I did not quite get it, could you post the full code so I can understand it better. Thank you so much for this, in order to keep it for other people, can you propose a name for this question?

And here is some questions: What is Environment? Is Android referring to Gallery by Directory? What is the startWatching() and the onEvent() methods

So would I do something like this?

String recoveryPhotoPath;
recoveryPhotoPath = 
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString();

Hey Farouk!

Yes, exactly what you have written is correct for the path.

Typically, we only provide pointers in the Community just so that we can get around to more people but I'm still willing to provide you with some code for you to take a look at.

I've gone ahead and set up a FileObserver in an activity, it looks a bit like this:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        // Get the path where pictures are generally stored.
        String recoveryPhotoPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
                .toString();
        // Let's just check where Android thought that was.
        Log.d("MainActivity", "Path: " + recoveryPhotoPath);

        // Let's create a new FileObserver. I've created it as an anonymous inner class here, you don't have to.
        FileObserver observer = new FileObserver(recoveryPhotoPath) {
            @Override
            public void onEvent(int event, String path) {
                // if the event is a DELETE event, run this code:
                if (event == FileObserver.DELETE) {
                    Log.d("MainActivity", "FILE DELETED AT " + path);
                    showToast();
                }
                // else if it's not, we're just going to break out of here. Let's not waste resources processing code!
            }
        };

        // Tell the observer to start watching for changes.
        observer.startWatching();
    }

    // Toasts need to be shown outside of the anonymous inner class.
    public void showToast() {
        Toast.makeText(this, "It's working!", Toast.LENGTH_LONG).show();
    }

Note that this is inside an activity and on most devices (This happened on mine when testing) you will find this code doesn't work as the activity gets destroyed when the app is closed. When the activity is destroyed, the observer then stops watching, so we're not notified of anything that happens. If you want to test it, you could delete a file by running code to do so inside your app.

This is where them Services that I mentioned earlier come into play - you can set one up so that the FileObserver remains watching, even when the app is closed. Go ahead and read this document to learn how to set one up! I would say a service is mandatory for making this type of app, so that it works on all devices.

As for your questions, Environment gives us access to environment variables. These are generally set by the phone manufacturer and allow us developers to say "Give me the pictures directory" to the Environment class and we'll then be given that directory for the specific device (Note that I have added a log statement just to check this, as it's not always correct so it may have to be adjusted for some devices). Hopefully this should also answer your second question in that we're using the Environment to get the directory where images are being stored.

As for the two methods, startWatching() is used to tell the FileObserver to start watching the directory we've specified for any changes. Nothing will happen if we don't call this method. onEvent() is called whenever there is an "event" relating to the files in the directory we're watching. This method is called whenever we try to access a file in the directory, create a new file, delete a file etc... The full list of events can be found on the Constants of FileObserver

Hopefully this should explain everything for you! As always, if you have any more questions, feel free to give me a shout :)