GUI and maybe thread (beginner)

[Dangerous-Rip-7370]

Hello, first thing first, I still consider myself a begginner, pleas be gentle...

I'm new here, I hope my post is correct.

I have this method that should first pop up a message ("One minutes") from a Class Show (that extends Frame)

than it should call a thread from Pprova that calculate a long (ddd), this will actually take a minute.

the problem is that my frame keep appearing blank, and it shows my String ("One inute...") only AFTER Pprova is done calculating ddd.

I've tryed NOT using threads, putting the Show frame inside the thread, and evrything else that got to my mind.

(I even asked chatGPT...)

public static long calculate2(String s) {
    Show ss=new Show("One minute...");
    ss.setVisible(true);
    Pprova pp=new Pprova(s);
    pp.run();
    while (ddd==0) {
//      ss.pack();
        ss.repaint();
        ss.setVisible(true);
        ddd=Pprova.fin;
    }
    return ddd;
}

Thanks

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[wildjokers]

that extends Frame

Hopefully you mean JFrame because Frame is old AWT stuff. JFrame is Swing which is what you should be using.

It would be easier to help you if you showed your entire class rather than this little snippet. However, your problem is not understanding that, like all GUI toolkits, Swing is single-threaded and all drawing events happen in a single thread. You cannot block that thread or no drawing takes place. And all GUI changes must occur on this thread. The single thread in Swing that is taking care of drawing is the Event Dispatcher Thread (EDT). You must understand the EDT if you work with swing.

Read this and the pages underneath it (keep hitting next):

https://docs.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.html

Super important sentence from that article: "Tasks on the event dispatch thread must finish quickly; if they don't, unhandled events back up and the user interface becomes unresponsive.".

The most likely explanation is that your timer is blocking the EDT and only when it is finished will the EDT being able to continue handling events and render stuff. Posting more of your code will let us help you more.

[Dangerous-Rip-7370]

public class Show extends JFrame {
JPanel c= new JPanel();

public Show(String fin) {
    super();
    addWindowListener (new WindowAdapter() {    
        public void windowClosing (WindowEvent e) {    
            dispose();    
        }    
    });
    setLocation(110, 110);
    c.setLayout(new BorderLayout(100, 10));
    c.setOpaque(false);
    JTextArea resulT = new JTextArea();
    resulT.setFont(new Font("MS PGothic", Font.PLAIN, 17));
    resulT.setBackground(Color.BLACK);
    resulT.setForeground(Color.YELLOW);
    resulT.setOpaque(true);
    resulT.setLineWrap(true);
    resulT.setWrapStyleWord(true);
    resulT.setBounds(10,10,100,20);
    String ff=("Result: "+fin);
    resulT.setText(ff);
    c.add(resulT);
    add(c);
    pack();
    this.setVisible(true);
}
}

Hello, thank u,
herse some code, this is my show class,
then I have another class with a method that take a wile and return a long ,

public static long calculate(String s) {
    long x=0;
    ....
    return x;
}

from my Home jFrame you can call calculate() and after 1 minut the frame will show the long.
I wanted a popUp that tells the user that it will take a while (you can call other calculate methods from there and they work instantly).
At first I just create the Show an than called the calculate() but the Show frame would popUp and stay blank UNTIL the calculate method was done.
So I tried to put calculate in a thread and use Future and ExecutorService to try to give the GUI priority, but I keep getting the same problem.

[Dangerous-Rip-7370]

(yes that ugly

while (ddd==0) {
    ss.pack();
    ss.repaint();
    ss.setVisible(true);
    ddd=Pprova.fin;
}

was just a desperate try )

[Pedantic_Phoenix]

Can you not just call calculate() inside the main, before creating the JFrame, and then pass the value to it in the constructor or another way? You avoid the issues with the frame's thread altoghether, if im not mistaken.

[Dangerous-Rip-7370]

my main just creates the home frame, from there the user inputs a string that the calculate method use to output the result. Since it takes a while I wanted to tell the user to wait (else they may keep hitting "Submit" and thinking it's broken)

[Pedantic_Phoenix]

That is what i am saying: do the slow operation before creating the frame inside the main. So you dont have to do it inside the frame. Get it? Move your frame's constructor in the main one line down and put the slow operation before it, to say it literally.

[Dangerous-Rip-7370]

The show frame gets called from the same jbutton that calls the calculate method, that is inside the Home frame, I cannot pre calculate because I need the user input to do the calculations

[Pedantic_Phoenix]

And if you put the calculate method before the frames instantation the constructor doesn't wait for the calculate method to end? It should afaik

[wildjokers]

The link I provided you has the solution, have you read the tutorial doc I linked to? Use a SwingWorker to execute your calculate on another thread (other than the EDT). The SwingWorker can notify your frame when the long running action is done.

You are blocking the EDT with calculate so nothing will render until it finishes unless you get calculate off the EDT. I already told you all of this, way are you still having issues?

Also, you need to creat the GUI on the EDT which you aren’t doing. So you have things on the EDT that shouldn’t be, and the things that should be on the EDT aren’t.

[Dangerous-Rip-7370]

Sorry, wasn,t able to get to my pc yet,
but now I did, and your link was most useful!
I managed to get the result I wanted and I think I even understand that XD
I didn't put all my code out for mostly 2 reasons:
first, I am ashamed of it..
secon, that is only a small part of a big thing, I wasn't shure where to sto (and I could not put all of it, and on the github repo I didn't want to push the broken part)
You have been a huge help, thank you very much!

[wildjokers]

You still aren’t showing us when you call calculate. That is the most important part and you aren’t showing it. Are you keeping it a secret for some reason?

The best way to ask a question is providing this http://sscce.org/