在 JFrame 中更新 JLabel

Question

I've been searching around this site and the internet for hours trying to figure out how to fix this problem. I'm creating a game and it's my first time using graphics. I figured out how to create a JFrame, JPanel and JLabel, and the only problem I can't seem to get around is updating the JLabel. Let's say I start it out like this:

JLabel testing = new JLabel ("blah", JLabel.CENTER);
testing.setAlignmentX(0);
testing.setAlignmentY(0);
frame.add(testing);

I am able to change the text after a Thread.sleep(2500) by using testing.setText("hi"); , but the previous state of the JLabel (which says blah) is still there. The "hi" just appears on top. I've tried testing.setVisible(false); , and so many other things but nothing is letting me display the JLabel, hide it, and then change it.

Any ideas what could be wrong? Thanks

Answer 1

Don't sleep or otherwise block on the AWT Event Dispatch Thread (EDT).

Use javax.swing.Timer instead. Note: not any other class of the same name in a different package.

            javax.swing.Timer timer =
                new javax.swing.Timer(2500, event -> {
                    testing.setText("hi");
                });
            timer.setRepeats(false);
            timer.start();