(JPanel switching ) add delay in seconds btween two panels switching (java)

Question

I am trying to add delay between two JPanels switching on same JFrame, both are changing visibility type in loop. I also try thread.sleep but it not working thanks in advance :)

panel 1 color is red

panel 2 color is black

 for (int i = 0; i < LENGTH; i++) {
    panel1.setVisible(true)
/*************************************
   here i want to add delay 
**************************************/  
    panel1.setVisible(false)
    panel2.setVisible(true);
    for (int k = 0; k < rSIZE; k++) {
        tempr[i][k].setBackground(labelsGrid[i][k].getBackground());
    }
}

Answer 1

You need to use Swing Timers to trigger delays between your UI toggling. Here's a simple example.

package app;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class App extends JFrame
{
    private JLabel label;
    private Timer timer;
    private int counter = 10; // the duration
    private int delay = 1000; // every 1 second
    private static final long serialVersionUID = 1L;

    public App()
    {
        super("App");
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        label = new JLabel("Wait for " + counter + " sec", JLabel.CENTER);
        JPanel contentPane = (JPanel) getContentPane();
        contentPane.add(label, BorderLayout.CENTER);
        contentPane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        pack();

        ActionListener action = new ActionListener()
        {   
            @Override
            public void actionPerformed(ActionEvent event)
            {
                if(counter == 0)
                {
                    timer.stop();
                    label.setText("The time is up!");
                }
                else
                {
                    label.setText("Wait for " + counter + " sec");
                    counter--;
                }
            }
        };

        timer = new Timer(delay, action);
        timer.setInitialDelay(0);
        timer.start();

        setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new App();
            }
        });
    }
}

This simple timer will trigger ActionListener every second and update label after decrementing counter values.