Question

Say if I have a Java Graphics object, and I want to draw a line or a rectangle on it. When I issue the command to draw, it appears on screen immediately. I just wonder how could I make this progress as a fade-in / fade-out effect, same as what you can achieve in Javascript.

Any thoughts?

Many thanks for the help and suggestions in advance!

Answer 1

You could try painting the image over and over again but with a different opacity (alpha) value. Start from 0 (completely transparent) and gradually increase to 1 (opaque) in order to produce a fade-in effect. Here is some test code which might help:

float alpha = 0.0f;

public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D) g;

    //set the opacity
    g2d.setComposite(AlphaComposite.getInstance(
            AlphaComposite.SRC_OVER, alpha));
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

    //do the drawing here
    g2d.drawLine(10, 10, 110, 110);
    g2d.drawRect(10, 10, 100, 100);

    //increase the opacity and repaint
    alpha += 0.05f;
    if (alpha >= 1.0f) {
        alpha = 1.0f;
    } else {
        repaint();
    }

    //sleep for a bit
    try {
        Thread.sleep(200);
    } catch (InterruptedException e) {

        e.printStackTrace();
    }
}