JTextArea append issue

[Ascalonian]

I am sure several of you have had this issue:

I have a JTextArea in one of my swing apps. At a given point, I am pumping a lot of text to the JTextArea via the append() method.

The issue I see is that it doesn't display right away. Rather, it hangs and won't display until the very end. I would like this to display each append individually.

I am pretty sure this is a threading issue. Anyone know a solution so that each line I am appending to the JTextArea can be seen?

Thanks!

 

[stefanwagner]

Search for a Tutorial about the event dispatching thread, EDT.

When you append from the EDT (because a button was clicked, i.e.), the EDT is blocked.

don't visit my homepage:

http://home.arcor.de/hirnstrom/minis/index.html

 

[Ascalonian]

I have tried all exampled I could find online and have not been able to get this to work. I tried invokeLater, using Runnable classes, and more.

Does anyone have a specific example for this?

Here is more info:

Throughout my Swing code, instead of writing anything to System.out, I write it to the JTextArea. I created a method to do the writing, which is below:

private void writeOutput(String newOutput) {
    outputData.setForeground(Color.BLACK);
		
    if(outputData.getText() != null) {
        saveButton.setEnabled(true);
    }
		
    outputData.append(newOutput + "\n");
    outputData.setForeground(Color.BLACK);
}

I am then calling this in a for-loop that has over 700 items. So this can be called 700+ times. However, it will not display until the very end.

Thank you all for your help.

 

[Ascalonian]

I actually got this to work. I was just looking at this incorrectly. I was trying to wrap the method writeOutput in a runnable... when I should have been wrapping the method that calls all those.

I had a method called validate() that had the for-loop inside. I had a JButton that had an ActionListener on it that called this method. I just had to make validate() be called from a Runnable.

So I had:

runButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ae) {
        // Some code checked on some radio buttons
        if(radioButton.isSelected()) {
            if(radioButton.getText().equals("VALIDATE")) {
               validate();
            }
        }
    }

});

And now I have:

class ValidateThread implements Runnable {
    public void run() {
        validate();
    }
}

runButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ae) {
        // Some code checked on some radio buttons
        if(radioButton.isSelected()) {
            if(radioButton.getText().equals("VALIDATE")) {
               Runnable runnable = new ValidateThread();
               Thread thread = new Thread(runnable);
               thread.start();
            }
        }
    }

});

Voila! This worked just fine. I added some other stuff to make sure the runButton will not be clicked again, but this is the important part.

Hope this helps anyone else!