Question

I asked a question last week about Gui and Timers… well after lots of research i found nothing that would work with my code… If anyone could take my code and somehow manipulate it to work that would be amazing… I want my code to display a box and then making it overlap with a box with the same color as the back ground and then a new box being displayed right beside it with a delay

first code:

import java.awt.Graphics;
import javax.swing.JPanel;
import java.awt.Color;

public class MovingSomething extends JPanel
{
    public void paintComponent (final Graphics g)
    {     
        int i = 20;
        int cons = 50;
        int red = 40;
        int green = 50;

        g.setColor(Color.GREEN);
        g.fillRect(50, 50, 100, 100);

        while (i >= 0)
        {
            i -= 1;

            g.setColor(Color.RED);
            g.fillRect(red, cons, 100, 100);
            red += 10;

            g.setColor(Color.GREEN);
            g.fillRect(green, cons, 100, 100);
            green += 10;
        }
    }
}

Answer 1

Just for your little help to start with, I am posting this code. Though Please do try to learn from it and ask valid questions, that might will arise, to get a taste of the whole thingy. If you had searched it a little bit harder, no doubt, you could have reached this wonderful Doc, that explains exactly your needs in this example.

Code to programatically repaint the component whenever the user clicks or drags the mouse

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

public class MovingSquare
{
    private int x = 0;
    private int y = 100;
    private final int WIDTH = 100;
    private CustomPanel canvas;
    private Timer drawingTimer;
    private ActionListener timerAction = 
        new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            if ((x + WIDTH == 500))
            {
                x = 0;
                canvas.setValues(x, y, Color.BLUE);
            }
            else
            {
                x += WIDTH;
                canvas.setValues(x, y, Color.BLUE);
            }
        }
    };

    private void displayGUI()
    {
        JFrame frame = new JFrame("Moving Sqaure");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        canvas = new CustomPanel();
        frame.setContentPane(canvas);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        drawingTimer = new Timer(1000, timerAction);
        drawingTimer.start();
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new MovingSquare().displayGUI();
            }
        });
    }
}

class CustomPanel extends JPanel
{
    private final int WIDTH = 500;
    private final int HEIGHT = 500;
    private final int WSQUARE = 100;
    private final int HSQUARE = 50;

    private int x = 0;
    private int y = 100;
    private Color cSquare = Color.BLUE;

    /* 
     * This is where we updating the state
     * of different variables needed, and
     * thus calling repaint.
     */
    public void setValues(int x, int y, Color color)
    {
        cSquare = color;
        repaint(this.x, this.y, WSQUARE, HSQUARE);
        this.x = x;
        this.y = y;
        repaint(x, y, WSQUARE, HSQUARE);
    }

    /*
     * Always make this one customary
     * habbit, to override this method
     * when you extending a JComponent.
     */
    @Override
    public Dimension getPreferredSize()
    {
        return (new Dimension(WIDTH, HEIGHT));
    }

    /* 
     * This is where the actual Painting
     * Portion of the whole thingy will
     * reside. Better is, not to put any
     * calculations in this part, just
     * update the state at some another
     * location and convey it to repaint
     * as needed.
     */
    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.setColor(cSquare);
        g.fillRect(x, y, WSQUARE, HSQUARE);
    }
}

LATEST EDIT :

Please try this modified code, the CustomPanel Class is same as before :

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

public class MovingSquare
{
    private int x = 0;
    private int y = 100;
    private final int WIDTH = 100;
    private final int HEIGHT = 100;
    private Random random;
    private CustomPanel canvas;
    private Timer drawingTimer;
    private ActionListener timerAction = 
        new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            /*if ((x + WIDTH > 500) && (y + HEIGHT > 500))
            {
                x = random.nextInt(500 - WIDTH);
                canvas.setValues(x, y, Color.BLUE);
            }
            else
            {
                x += WIDTH;
                canvas.setValues(x, y, Color.BLUE);
            }*/
            x = random.nextInt(500 - WIDTH);
            y = random.nextInt(500 - HEIGHT);
            canvas.setValues(x, y, new Color(
                random.nextFloat(), random.nextFloat()
                , random.nextFloat(), random.nextFloat()));
        }
    };

    public MovingSquare()
    {
        random = new Random();
    }

    private void displayGUI()
    {
        JFrame frame = new JFrame("Moving Sqaure");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        canvas = new CustomPanel();
        frame.setContentPane(canvas);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        drawingTimer = new Timer(1000, timerAction);
        drawingTimer.start();
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new MovingSquare().displayGUI();
            }
        });
    }
}