If you simply return from update() without rendering anything then
repaint() calls will have no effect. The typical way to relieve
flickering is to have update() call paint() directly as in:
public void update(Graphics g) {
paint(g);
}
...jim
Ken Warner wrote:
Jim,
I figured out my problem. It had nothing to do with MemoryImageSource.
It was all my own dumb mistake. I've been almost entirely programming
in Swing for the last 5 years. Swing does all the buffering.
I started a little applet project in AWT just to get a small, light, fast
applet. It turns out that Component.update() either has changed or what
I was doing before never had a problem with update().
update() clears the drawing area -- in this case a Canvas -- to the
background
color and then calls paint(). One must over ride update() to stop the
flickering and tearing. I just override update in MyCanvas to a stub.
update()
{
return;
}
Either I knew this once and forgot or it's changed since the last time
I made my own custom component from Canvas. It was all me.
And I pretty much am relying on BufferStrategy now so no offscreen drawing
what so ever. It works flawlessly now.
Thanks for responding....
Ken
Jim Graham wrote:
When you set the animated attribute to true on a MIS it will never be
"complete" so drawImage will never return true.
The return value of drawImage should probably be ignored for
99.999999% of code - it doesn't tell you anything that you really need
to know. All it is telling you is if all of the image data has been
completely loaded from the source, but your ImageObserver will be
notified when new data is available so there isn't much you need to do
with the return value other than its informative (novelty?) value. In
particular, if you immediately reissue the drawImage call it will
paint exactly the same thing it painted the previous time until new
data arrives (which isn't likely to happen if you are wasting all of
the CPU time repainting something that hasn't changed yet).
With respect to the change in behavior in 1.4 vs. 1.5, I'm not sure
what might be causing that without a standalone test case. The only
odd thing I see is that you are double buffering things - dumping
pixels into canvasImage with newPixels and then immediately
transferring them to buffer with drawImage and later the pixels get
dumped from buffer to the screen with the drawImage in the paint
method - why not just use the drawImage to the screen directly?
...jim
Ken Warner wrote:
I'm haveing a strange problem -- I've used MemoryImageSource before with
great success. But now, doing the same thing I've done before in
Java 1.4
I'm getting flickering on newPixels() in Java 1.5...
That is, when I send new pixels to my MemoryImageSource mis and
repaint() the image flickers badly. Didn't do this in 1.4.
The odd thing is that --
while((status = bg.drawImage(canvasImage,0,0,thisW, thisH,this)) ==
false);
never breaks because bg.drawImage never returns true. Do I have to
use a MediaTracker
or something???
Here's what I'm doing -- I've tried it using BufferStrategy and get
the same flicker
//this is an AWT Canvas
private Image canvasImage = null;
private Image buffer = null;
private Graphics2D bg = null;
private MemoryImageSource mis = null;
private ColorModel cm = null;
init()
{
thisW = this.getWidth();
thisH = this.getHeight();
mis = new MemoryImageSource(thisW,thisH,pixels,0,thisW);
mis.setAnimated(true);
mis.setFullBufferUpdates(true);
canvasImage = this.createImage(mis);
buffer = this.createImage(thisW, thisH);
bg = (Graphics2D)buffer.getGraphics();
}
public void paint(Graphics g)
{
g.drawImage(buffer,0,0,thisW, thisH,this);
}
public void newPixels(int [] newPixels)
{
mis.newPixels(newPixels, ColorModel.getRGBdefault(),0, thisW);
boolean status = false;
//while((status = bg.drawImage(canvasImage,0,0,thisW,
thisH,this)) == false);
bg.drawImage(canvasImage,0,0,thisW, thisH,this);
this.repaint();
}
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