Changing colors slowly, Java Graphics

Question

I have a gradient background and I want, slowly, for it to change colors, basically for it to go through different colors. The color has to blend through all the colors, I do not want it to flick through colors, is this possible? Please enlighten me with a solution, thanks.

Answer 1

Also consider java.awt.image.MemoryImageSource and a javax.swing.Timer, illustrated here and below.

Answer 2

Really too hard to say anything (whatever clever) to my defense, (try & enjoy)

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Random;
import javax.swing.*;

public class GradientPaintWithSwingTimerAndRunnable extends JFrame implements Runnable {

    private static final long serialVersionUID = 1L;
    private Queue<Icon> iconQueue = new LinkedList<Icon>();
    private JLabel label = new JLabel();
    private Random random = new Random();
    private JPanel buttonPanel = new JPanel();
    private JPanel labelPanel = new JPanel();
    private Timer backTtimer;
    private Timer labelTimer;
    private JLabel one = new JLabel("one");
    private JLabel two = new JLabel("two");
    private JLabel three = new JLabel("three");
    private final String[] petStrings = {"Bird", "Cat", "Dog",
        "Rabbit", "Pig", "Fish", "Horse", "Cow", "Bee", "Skunk"};
    private boolean runProcess = true;
    private int index = 1;
    private int index1 = 1;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                GradientPaintWithSwingTimerAndRunnable t = new GradientPaintWithSwingTimerAndRunnable();
            }
        });
    }

    public GradientPaintWithSwingTimerAndRunnable() {
        iconQueue.add(UIManager.getIcon("OptionPane.errorIcon"));
        iconQueue.add(UIManager.getIcon("OptionPane.informationIcon"));
        iconQueue.add(UIManager.getIcon("OptionPane.warningIcon"));
        iconQueue.add(UIManager.getIcon("OptionPane.questionIcon"));

        one.setFont(new Font("Dialog", Font.BOLD, 24));
        one.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        two.setFont(new Font("Dialog", Font.BOLD, 24));
        two.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        three.setFont(new Font("Dialog", Font.BOLD, 10));
        three.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        labelPanel.setLayout(new GridLayout(0, 3, 4, 4));

        labelPanel.add(one);
        labelPanel.add(two);
        labelPanel.add(three);
        //labelPanel.setBorder(new LineBorder(Color.black, 1));
        labelPanel.setOpaque(false);

        JButton button0 = createButton();
        JButton button1 = createButton();
        JButton button2 = createButton();
        JButton button3 = createButton();

        buttonPanel.setLayout(new GridLayout(0, 4, 4, 4));
        buttonPanel.add(button0);
        buttonPanel.add(button1);
        buttonPanel.add(button2);
        buttonPanel.add(button3);
        //buttonPanel.setBorder(new LineBorder(Color.black, 1));
        buttonPanel.setOpaque(false);

        label.setLayout(new BorderLayout());
        label.add(labelPanel, BorderLayout.NORTH);
        label.add(buttonPanel, BorderLayout.SOUTH);
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        label.setPreferredSize(new Dimension(d.width / 3, d.height / 3));

        add(label, BorderLayout.CENTER);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
        startBackground();
        startLabel2();
        new Thread(this).start();
        printWords(); // generating freeze Swing GUI durring EDT
    }

    private JButton createButton() {
        JButton button = new JButton();
        button.setBorderPainted(false);
        button.setBorder(null);
        button.setFocusable(false);
        button.setMargin(new Insets(0, 0, 0, 0));
        button.setContentAreaFilled(false);
        button.setIcon(nextIcon());
        button.setRolloverIcon(nextIcon());
        button.setPressedIcon(nextIcon());
        button.setDisabledIcon(nextIcon());
        nextIcon();
        return button;
    }

    private Icon nextIcon() {
        Icon icon = iconQueue.peek();
        iconQueue.add(iconQueue.remove());
        return icon;
    }

    // Update background at 4/3 Hz
    private void startBackground() {
        backTtimer = new javax.swing.Timer(750, updateBackground());
        backTtimer.start();
        backTtimer.setRepeats(true);
    }

    private Action updateBackground() {
        return new AbstractAction("Background action") {

            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent e) {
                label.setIcon(new ImageIcon(getImage()));
            }
        };
    }

    // Update Label two at 2 Hz
    private void startLabel2() {
        labelTimer = new javax.swing.Timer(500, updateLabel2());
        labelTimer.start();
        labelTimer.setRepeats(true);
    }

    private Action updateLabel2() {
        return new AbstractAction("Label action") {

            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent e) {
                two.setText(petStrings[index]);
                index = (index + 1) % petStrings.length;
            }
        };
    }

    // Update lable one at 3 Hz
    @Override
    public void run() {
        while (runProcess) {
            SwingUtilities.invokeLater(new Runnable() {

                @Override
                public void run() {
                    one.setText(petStrings[index1]);
                    index1 = (index1 + 1) % petStrings.length;
                }
            });
            try {
                Thread.sleep(300);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    // Note: blocks EDT
    private void printWords() {
        for (int i = 0; i < petStrings.length; i++) {
            String word = petStrings[i].toString();
            System.out.println(word);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            three.setText(word);
        }
        three.setText("<html> Concurency Issues in Swing<br>"
                + " never to use Thread.sleep(int) <br>"
                + " durring EDT, simple to freeze GUI </html>");
    }

    public BufferedImage getImage() {
        int w = label.getWidth();
        int h = label.getHeight();
        GradientPaint gp = new GradientPaint(0f, 0f, new Color(
                127 + random.nextInt(128),
                127 + random.nextInt(128),
                127 + random.nextInt(128)),
                w, w,
                new Color(random.nextInt(128), random.nextInt(128), random.nextInt(128)));
        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = bi.createGraphics();
        g2d.setPaint(gp);
        g2d.fillRect(0, 0, w, h);
        g2d.setColor(Color.BLACK);
        return bi;
    }
}