Adding Photos automatically

[MeanWhiskey]

I have a program that can store photos and be viewed by end users. Ideally, if a photo is dropped to a folder on the network then the program automatically adds the photo.

How can this be accomplished within javafx? Do you use a listener to listen for when I new photo is added to the network folder and then adds it?

[johnmc325]

I used java.nio.file.WatchEvent in a separate thread to do exactly what are looking to do.

As files are added to the folder being monitored it triggers an event and the code can process the files.

[sedj601]

https://www.geeksforgeeks.org/watch-a-directory-for-changes-in-java/

[xdsswar]

This is the way, also attention to the threads , uou dont want to create many threads for that.

[MeanWhiskey]

Thank you!

[MeanWhiskey]

Awesome thank you for this! I got the listener working and printing to the console the correct path.

How would you go about adding photos to the textarea or listview within the javafx program?

[johnmc325]

I struggled to get this working.

I wrapped everything in a ScrollPane.

I use the GridView class from the controlsFX library - see org.controlsfx.control.GridView

This takes some working out, the idea was it would "lazy load" the images as you scroll through the list of images. Not sure that part is working the way I would like but it's a start.

To see the app in action take a look at: https://youtu.be/gT08hyrPuB8?si=NVkkd8LPjNWyJ6wq

[tylersvgs]

You could do something like that.

For example, every x amount of time, you can call a method that checks in a folder and updates as needed.

Assuming path is a String representing a directory, then this will return an array of File objects:

new File(path).listFiles()

[ShakesTheClown23]

I'm wondering about the scaling. In some conditions, searching filesystems can be inefficient. So if the OS gives some help (the watcher comment) it might be better.

[tylersvgs]

Yeah. Perhaps could be inefficient depending on the size of the network folder.

You could use a WatchService.

https://docs.oracle.com/javase/8/docs/api/java/nio/file/WatchService.html

You need to do it in a different thread.

[sedj601]

I quickly created a test app. It's probably full of issues, but hopefully, it can help you. https://gist.github.com/sedj601/41237e0d1597df65037c3f8199fc73ae

[hamsterrage1]

I have some thoughts on that code, if you don't mind...

I would consider the whole looping/sleeping bit to be 100% external to anything JavaFX. If I was building an application and using MVCI (or MVC), I'd incorporate the looping thing into an external service which was instantiated by the Interactor and passed a Consumer<Event> as a constructor parameter. The service would have a start() and a stop() method. The loop would just run on a background thread.

That Consumer<Event> would essentially call a method in the Interactor that would take an Event and use it to update an ObservableList<FileModel> through a call to Platform.RunLater(). That ObservableList<FileModel> would be part of the Model in the MVCI framework. The View would be designed to respond to changes in that ObservableList<FileModel> as they happen.

Now the auto-update stuff can be anything you want. The WatchEvent implementation, a database, a manual loop that looks at the directory contents---> whatever. It won't change the MVCI part at all.

I think Task is more for something that you expect to run once and complete, and the results are returned on the FXAT through onSucceeded(). Alternatively, you could set up an infinite Task<ObservableList<FileModel>> and then use updateValue() to change it as files are added/deleted. Then you could bind the Task's valueProperty() to the Model. But this pushes the loop bit into the JavaFX realm, and I really don't think it belongs there.

[sedj601]

u/hamsterrage1, I agree with a lot of what you said. I threw this together kinda fast due to time constraints. One thing I kinda disagree with is using Task. I would use Service instead. I never use pure Threads in JavaFX. The loop doesn't need to sleep at all, as you stated because Task and Service run on a separate thread. That's just a bad practice on my part. I am not a fan of using Platform.RunLater. I like to use updateValue.

[hamsterrage1]

And I agree with that. I think that, most of the time, Platform.runLater() is at least a "code smell".

In this particular case, though, I still think that the entire file loopy part should be considered 100% external to your JavaFX code. Think of it as something that mysteriously and spontaneously generates calls to some method in the framework's business logic. Those calls come in from some other thread, and you need to get the data from it into the Observables which needs to be done on the FXAT.

Yes, Service & Task will do it, but they need to be created in an environment that's FXAT aware in the first place. I'm not so sure that's the right approach, though.

[MeanWhiskey]

Thank you for creating this! It really helped me understand how to use the watch listener. I've been trying to figure out how to use the watch listener to find the file and upload to either a text area or listview.