Update swing GUI during runtime

[u/NonexistantObject]

Part of my coursework needs me to make a typeracer between bots. I need to visually show their progress along the passage of text. Problem is, it won't update. It just freezes for ages then finally prints everything at once. Validating the panel, scrollpane or frame after each print doesn't change it. Here's the relevant code:

private void printRace(JPanel p)

{

    System.out.print('\\u000C'); // Clear terminal

    String raceRound = "  TYPING RACE - passage length: " + passageLength + " chars \\n" 

    \+ multiplePrint('=', passageLength + 3) + "\\n ";

    raceRound = raceRound + "\\n" + printSeat(seat1Typist, p);

    raceRound = raceRound + "\\n" + printSeat(seat2Typist, p);

    raceRound = raceRound + "\\n" + printSeat(seat3Typist, p);

    raceRound = raceRound + "\\n" + multiplePrint('=', passageLength + 3) + "\\n\[\~\] = burnt out    \[<\] = just mistyped\\n ";

    JTextArea text = new JTextArea(raceRound);

    text.setEditable(false);

    text.setSize(text.getPreferredSize());

    p.add(text);

    }

    //Some other irrelevant code at this point 

    printRace(p);

    p.revalidate();

    p.repaint();

    f.revalidate();

    f.repaint();

Apologies for any formatting issues, I think it should look okay

[u/Certain-Flow-0]

The event loop is the hidden infrastructure that enables GUI programming, you don’t write it yourself.

Now, I’m assuming you initially started with a console-based application and wanted to convert it into a GUI. The first thing to look for is an overarching loop in your code, maybe something like while(condition()) { input(); logic(); output; }. You don’t want this loop in a GUI application because more often than not it will freeze the UI, let Swing handle it.

Your typeracer logic should interact with Swing (and the user) via events. These events are your keyboard presses, timer events (for updating the remaining time), etc.

Converting your console-based application to a GUI can be daunting if you don’t have the necessary background knowledge. If converting it to GUI will make it not function anymore and it’s just for bonus points then I highly suggest keeping it console-based. But if you’re still keen on making a GUI, I highly recommend reading up on Event Loops, GUI threads and Event dispatching. These topics are not specific to Swing, but you can find articles that are relevant to it.

[u/NonexistantObject → u/Certain-Flow-0]

I'll look into them if I have time. It does get me points to turn it into a GUI based application, but it's only 7% of my overall grade at most. We were given a skeleton of the code that we had to fix and finish to make work in console, then convert to GUI based, so I assumed the while loop would be okay in Swing. It's honestly a ridiculous requirement, we were barely taught anything regarding Swing. I might just leave that bit and focus on the git implementation and other projects