Why doesn't setText work for JLabel component?

Question

I have a JLabel which I want to change momentarily, here is the code I have written to do so:

infoLabel.setText("Added");
try {
   TimeUnit.MILLISECONDS.sleep(300);
}
catch(InterruptedException ex)
{
}

infoLabel.setText("Action"); //funny part is when I comment this line it works

My default text for the label is 'Action'

Wow! We've never seen a problem like this before. Well at least, never before in this particular *hour*. Try searching in future.. — Andrew Thompson, Oct 28 '13 at 02:26
sarcasm buddy? well its kinda difficult to search for this in the net for me — Snedden27, Oct 28 '13 at 03:52

MadProgrammer · Accepted Answer · 2013-10-28T02:25:28.187

Swing is a single threaded frame work, that means, if you do anything that stops this thread, then it can't respond to any new events, including paint requests.

Basically, TimeUnit.MILLISECONDS.sleep(300) is causing the Event Dispatching Thread to be put to sleep, preventing it from processing any new paint requests (amongst other things).

Instead, you should use a javax.swing.Timer

Take a look at

For more details

For example...

infoLabel.setText("Added");

Timer timer = new Timer(300, new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        infoLabel.setText("Action");
    }
});
timer.setRepeats(false);
timer.start();

Note, 300 milliseconds is a really short time, you might like to start with a value a little larger like 2000, which is 2 seconds ;)

score 1 · Answer 2 · answered Oct 28 '13 at 02:20

1

You're sleeping the Swing event thread putting the entire GUI to sleep. Don't do that. Use a Swing Timer instead.

answered Oct 28 '13 at 02:20

Hovercraft Full Of Eels

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score 0 · Answer 3 · answered Oct 28 '13 at 02:20

0

Your application is run on a single thread, so when you sleep the thread, you prevent it from making any GUI updates.

answered Oct 28 '13 at 02:20

Matt Clark

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score 0 · Answer 4 · edited May 23 '17 at 11:50

0

Are you sure you are doing things properly? By doing everything (including sleep) in the GUI thread, it will always be busy and never get back to Java in order to let the GUI be redrawn.

Search for EDT (Event dispatch thread) for more info. Here is one question on the subject: Processing code doesn't work (Threads, draw(), noLoop(), and loop())

edited May 23 '17 at 11:50

Community

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answered Oct 28 '13 at 02:21

John3136

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Why doesn't setText work for JLabel component?

4 Answers4