How to change a JLabel text for x Seconds

问题

I want to change the JLabel text for a short moment (there's a counter and if someone types in the wrong answer in a text field, I want to show a "wrong answer" instead of the counter. After a few seconds I want to show the counter again.)

回答1:

For the fixed-delay execution of some code you want to use a timer object, in this case javax.swing.Timer. Here is a demo that applies to your situation:

public static void main(String[] args) {
    SwingUtilities.invokeLater(()->{
        JFrame frame = new JFrame();
        frame.setLayout(new FlowLayout());
        JLabel label = new JLabel("One");
        JButton button = new JButton("Ok");
        button.addActionListener(e -> {
            String oldText = label.getText();
            label.setText("Changed");
            Timer timer = new Timer(2000, event -> {
                label.setText(oldText);
            });
            timer.setRepeats(false);
            timer.start();
        });
        frame.add(label);
        frame.add(button);
        frame.pack();
        frame.setVisible(true);
    });
}

The listener for the button changes the text of the label and starts a Swing timer (here with a fuse of 2 seconds). Once the timer times out, it sends an action event to its (the timer's) registered listener, which in this case reverts the text to the original one.

回答2:

Use a variable from outside your paint() void, to tell your paint() method to draw over or not draw the counter on the screen. For example,

boolean wrongAnswer = true;
public void paint(Graphics g){
    if(b){
        g.drawString("Wrong Answer.", x, y);
        //It's best to use a timer, see the link provided
    }
    else{
        g.drawString(counter+"", x, y)
    }
}

why not to use thread.sleep for no reason, and explain it to a programmer

回答3:

// change text to error
Thread.sleep(5000); // 5000ms = 5 seconds
// change text to counter

This a easy how you could do it. Obviously you should replace the comments with actual code.

来源：https://stackoverflow.com/questions/58357255/how-to-change-a-jlabel-text-for-x-seconds

标签

java

swing

timer

jlabel