Why is screen flashing when I call repaint()?

[colin shuker]

Hi, I'm pretty new to applets, but I'm trying to turn my Fractal
explorer program into an applet.
In the original application, I was calling the paintComponent(Graphics g) method, and within this, I was displaying a image, as well as other things, and whenever I had to repaint() the frame many times, it was fine.

But now, I'm using an applet and a paint(Graphics g) method. Again I'm initially displaying an image, and a moving box, but whenever repaint() is called, the screen flashes, the basic code is shown below:

public void paint(Graphics g)
{
   super.paint(g);
   g.drawImage(images[n],0,0,this);
   Graphics2D g2 = (Graphics2D)g;
   g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                       RenderingHints.VALUE_ANTIALIAS_ON);
   // more code here to draw box
   //    
}

I didn't want to use a JFrame, becuz I wanted the output to go into a rectangle on the HTML screen.
There is an alternative I can think of, using an OverlayLayout, but
I would rather see if there is anyway around this first.
Thanks for any help.

[Ernest Friedman-Hill]

Short answer: use a JApplet instead of an Applet, and use paintComponent(). You'll get double-buffering just like you got in your JFrame.

[colin shuker]

Ahh, but hmmm.
I was invoking this from an HTML file using the tag:

<APPLET code="FractalApplet.class" width=500 height=500></APPLET>

So would that still be ok, to use that?

OK, sorry, I just checked API, and JApplet extends Applet, so it should be ok.
[ November 02, 2005: Message edited by: colin shuker ]

[colin shuker]

I just tried extending JApplet instead of applet, and using paintComponent
instead of paint, and it didn't work.
Can't see why?
Any ideas?

[Ulf Dittmer]

it didn't work.

What does that mean?

[colin shuker]

Oh sorry, I should have explained better.
Using JApplet instead of Applet, and paintComponent(Graphics g) instead of paint(Graphics g) now just shows a blank grey screen, except for the panel of 4 buttons at the bottom.

I've created a new small JApplet (see my other post about JApplet), I can't
even get this to draw a line.
I'm probably missing something stupid, but I don't know what.
Any advice is much appreciated, thanks.

[Ulf Dittmer]

I've never used JApplets, but there's an introduction over at java.sun.com.

[colin shuker]

Thanks, I was looking at it earlier.
I looked at an example, they had an inner class of the class that extends
JApplet, which extended JPanel.
I copied this idea for my applet, but it wouldn't upload when I tried to
use Geocities for my website, because of the $ in the inner class name.

But then I figured out how to write the classes separatly and it worked.
Its taken me the whole day to get this far, but I've finally done it.