Question

I need one colour fading example which is written in Java.
My requirement is I have two rectangles. One is filled up with colour red and another is filled up with white. When I click any button, I want that red colour to start fading and moving green colour. Once it is reached to green position then automatically another rectangle should start from yellow blue. Could anybody help me on this? If any example got which is written in Javaswing or SWT will be good. Thanks.

Answer 1

Checkout Trident animation library. It allows you to easily interpolate properties in your class. Also check these original tutorials from Kirill Grouchnikov (the author of Trident).

EDIT: animation example w/o Trident

The following sample is based on AnimatedGraphics example in Filthy Rich Clients:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class AnimatedGraphics extends JComponent implements ActionListener {

    Color startColor = Color.RED;   // where we start
    Color endColor = Color.GREEN;         // where we end
    Color currentColor = startColor;
    int animationDuration = 2000;   // each animation will take 2 seconds
    long animStartTime;         // start time for each animation

    public AnimatedGraphics() {
        Timer timer = new Timer(30, this);
        // initial delay while window gets set up
        timer.setInitialDelay(1000);
        animStartTime = 1000 + System.nanoTime() / 1000000;
        timer.start();
    }

    public void paintComponent(Graphics g) {
        g.setColor(getBackground());
        g.fillRect(0, 0, getWidth(), getHeight());
        g.setColor(currentColor);
        g.fillOval(0, 0, getWidth(), getHeight());
    }

    public void actionPerformed(ActionEvent ae) {
        // calculate elapsed fraction of animation
        long currentTime = System.nanoTime() / 1000000;
        long totalTime = currentTime - animStartTime;
        if (totalTime > animationDuration) {
            animStartTime = currentTime;
        }
        float fraction = (float)totalTime / animationDuration;
        fraction = Math.min(1.0f, fraction);
        // interpolate between start and end colors with current fraction
        int red = (int)(fraction * endColor.getRed() + 
                (1 - fraction) * startColor.getRed());
        int green = (int)(fraction * endColor.getGreen() + 
                (1 - fraction) * startColor.getGreen());
        int blue = (int)(fraction * endColor.getBlue() + 
                (1 - fraction) * startColor.getBlue());
        // set our new color appropriately
        currentColor = new Color(red, green, blue);
        // force a repaint to display our oval with its new color
        repaint();
    }

    private static void createAndShowGUI() {    
        JFrame f = new JFrame("Animated Graphics");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(200, 200);
        f.add(new AnimatedGraphics());
        f.setVisible(true);
    }

    public static void main(String args[]) {
        Runnable doCreateAndShowGUI = new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        };
        SwingUtilities.invokeLater(doCreateAndShowGUI);
    }
}