How do I make my for loop delay for 1 second between iterations on JFrame?

Question

This is my function so far:

    public void slow_print(final String s, int interval){
        for (int i=0; i<s.length(); i++){
            txta_main.setText(
                txta_main.getText()
                + String.valueOf(s.charAt(i))
            );
        }
    }

I don't know how to make it wait in between setText calls. I can't use Thread.sleep as this is on a GUI and the sleep freezes the output until the whole string is done.

Answer 1

Use a Swing Timer for basic animation.

The Timer replaces your looping logic.

Every time the timer fires your increment your "index" variable and perform your processing.

Here is a simple that example that simply increments the index variable and stops when processing has completed 10 cycles.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;

public class TimerStop extends JPanel implements ActionListener
{
    private JLabel timeLabel;
    private int count = 0;

    public TimerStop()
    {
        timeLabel = new JLabel( new Date().toString() );
        add( timeLabel );

        Timer timer = new Timer(1000, this);
        timer.setInitialDelay(1);
        timer.start();
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        timeLabel.setText( new Date().toString() );
        count++;
        System.out.println(count);

        if (count == 10)
        {
            Timer timer = (Timer)e.getSource();
            timer.stop();
        }
    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("TimerStop");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new TimerStop() );
        frame.setLocationByPlatform( true );
        frame.pack();
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}

So you simply modify the timer logic to append a character to the text string each time the Timer fires and stop the timer then all the text is displayed.