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So the program I am making uses 2 threads: One for the GUI and one to do the work.

I want updates from the work thread/class to print out on JTextArea in GUI class. Everything I tried didn't seem to work. I added lines to print out text on the console right after lines to add text to the JTextArea to make sure it had got to the line but everytime console got text but no changes happened to JTextArea in the GUI.

public static void consoleText(String consoleUpdate){
    GUI.console.append(consoleUpdate);
}

I tried this in the work class but nothing happened. Anyone know how to fix my problem?

Edit:

MAIN.JAVA

public class main {
public static void main(String[] args) {
    Thread t1 = new Thread(new GUI());
    t1.start();
}

GUI.JAVA

public class GUI extends JFrame implements Runnable{

public static JTextArea console;
private final static String newline = "\n";

public void run(){
    GUI go = new GUI();
    go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    go.setSize(350, 340);
    go.setVisible(true);
}

public GUI(){
setLayout(new FlowLayout());
console = new JTextArea(ConsoleContents, 15, 30);
add(console);
}

WORK.JAVA

...{
consoleText("\nI want this text on the JText Area");
}

public static void consoleText(String consoleUpdate){
    GUI.console.append(consoleUpdate);
}
Emm
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    no idea how to anyone can help you with that, for better help sooner post an [SSCCE](http://sscce.org/) , short, runnable, compilable, only about `JTextArea#append("String")` – mKorbel Oct 24 '12 at 16:11
  • welcome on this forum, please [see FAQ](http://stackoverflow.com/faq) – mKorbel Oct 24 '12 at 16:12
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    Ok I'll try truncate it enough to post – Emm Oct 24 '12 at 16:15
  • I'm no expert on Swing, but everything I've ever seen is to make your GUI in a Runnable instead of a Thread. I couldn't even tell you why, but that's just what I've seen. Someone else may comment to correct me. – Andy Oct 24 '12 at 16:26
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    @Andy Runnable is just a way to wrap some job to do in a class. Thread is directly related to parallel execution. Anyway, in Swing, everything (GUI-related) should be performed on the EDT (Event Dispatching Thread) and a simple technique to ensure that your code is run on the EDT, is to wrap it in a `Runnable` and give it to `SwingUtilities.invokeLater(Runnable)`. This may have you lead to think that you need a Runnable rather than a Thread. – Guillaume Polet Oct 24 '12 at 16:48
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    Here's an [example](http://stackoverflow.com/a/3245805/230513). – trashgod Oct 24 '12 at 16:57
  • Thanks :) It works fine now; how do I set my question to "answered"? – Emm Oct 25 '12 at 08:13

1 Answers1

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First, as has been said, your GUI should only run on the Event dispatch thread.

As it is written, your GUI class does two things : it's a frame, and a runnable, and both are used completely independently. As a matter of fact, calling "run" on a your GUI object creates another, unrelated GUI object. That's probably the reason why you see nothing.

So I suggest making your main the following:

... main(...) {
  SwingUtilities.invokeLater(new Runnable() {
      public void run() {
          GUI gui= new GUI();
          gui.setVisible(true); // and other stuff
      }
  });
}

(I would also suggest getting rid of all "static" fields BTW. It's probably the source of your problems, along with the weird place of the "run" method).

Now, your "consoleText" method, which I assume you call from another thread, should not modify the text directly, but call SwingUtilities.invokeLater() to do so :

public void consoleText(final String consoleUpdate){
 SwingUtilities.invokeLater(new Runnable() {
    public void run() {
      console.append(consoleUpdate);
    }
 });

}

(the "final" declaration is important, as it allows the Runnable to use the consoleUpdate variable).

khaemuaset
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