Thread: JavaFX - Main Program Loop

Hey, I'm working on my first JavaFX GUI for a Torrent Client I'm working on. I'm a little confused by the program flow.

In the code bellow you can see what I tried to do in the block for the File Select Button. I wanted to output text to the TextArea as the program runs updating the user on whats happening as some of the methods take a long time. You can see "textbox.setText("Contacting Tracker...");" and "textbox.setText("Getting peers...");". Obviously at that point the program has not reached Stage.show() so they are never outputted.

I know the way I have tried to do that is completely wrong and I have no idea of the correct way to implement it. I also would want TableView to be updated as soon as a new item is added to the ObservableList - displaylist not after all the code that follows it.

public class Main extends Application {
    int lastindex = 0;
 
    @Override
    public void init(){
    }
 
    @Override
    public void start(Stage stage){
        //crate list of torrents
        TorrentList torrentList = new TorrentList();
 
        ObservableList<Display> displaylist = FXCollections.observableArrayList();
        TableView<Display> table;
 
        //Text Box
        TextArea textbox = new TextArea();
        textbox.setPrefRowCount(4);
        textbox.setPrefHeight(150);
        textbox.setPrefWidth(300);
 
        //file select button
        FileChooser fileChooser = new FileChooser();
        Button openfile = new Button("Open Torrent");
        openfile.setOnAction(e -> {
            File selectedFile = fileChooser.showOpenDialog(stage);
            torrentList.Add(selectedFile);
            lastindex = torrentList.getLast();
 
            displaylist.add(new Display());
            displaylist.get(lastindex).setId(lastindex);
            displaylist.get(lastindex).setName(torrentList.List.get(lastindex).getName());
 
            textbox.setText("Contacting Tracker...");
            torrentList.List.get(lastindex).printAll();
            torrentList.List.get(lastindex).tracker.printall();
            textbox.setText("Getting peers...");
            torrentList.List.get(lastindex).tracker.getPeers();
            torrentList.List.get(lastindex).tracker.peers.printpeers();
            textbox.setText("");
 
        });
 
        //table columns
        TableColumn<Display, Integer> idcolumn = new TableColumn<>("ID");
        idcolumn.setMinWidth(100);
        idcolumn.setCellValueFactory(new PropertyValueFactory<Display, Integer>("id"));
 
        TableColumn<Display, String> namecolumn = new TableColumn<>("Name");
        namecolumn.setMinWidth(300);
        namecolumn.setCellValueFactory(new PropertyValueFactory<>("name"));
 
        //setup table
        table = new TableView<>();
        table.setItems(displaylist);
        table.getColumns().addAll(idcolumn, namecolumn);
 
        HBox root = new HBox();
 
        root.getChildren().addAll(table, openfile, textbox);
 
        Scene scene = new Scene(root, 900, 250);
        stage.setTitle("Rabbit Torrent");
 
        stage.setScene(scene);
        stage.show();
    }
 
    @Override
    public void stop(){
    }
 
}

Messing around with the GUI made me realise that the main guts of the actual program (not implemented above yet) need to run in a loop. I have no idea of how to have a main program loop inside the javaFX GUI code.

Originally Posted by Norm

Also posted at https://coderanch.com/t/714250/java/...n-Program-Loop

Yeah that was me. I posted on both forums.

^Ah I didn't know. Want me to delete one?

I had a similar disappointment with the way JavaFX expects you to start your program. The init() function is nice for background initialization, but try showing a GUI splash screen from there. Not happening!

What I did was make the start() function just spawn a new thread for all the background initialization work. Then the worker thread calls stage.show() near the beginning and then has a visible GUI to update while it's working. Remember to use Platform.runLater(Runnable r) when updating JFX components (including showing stages) from a non-GUI thread.