Smoother animation - Please help...

Question

Hi,
I'm writing a graphical editor where multiple shapes can be moved , resized and so on.
Let's say I want to move around a rectangular Shape.
*What is the best way to avoid redrawing all the elements of the screen - just the ones that get "dirty" by the Shape's movement??? If I keep all the Shapes in a Vector , then test which Shapes intersect with the moving box and only redraw those - would that be a fast or a slow thing to do???
*Is there any way to take a "screenshot" of the shapes that stay foot so that I least I won't have to regenerate all the shapes to be drawn , just "paste" this screenshot then draw above it the box in its new position??? ( I mean something like copyArea(x,y,width,height, 0 , 0 )
* If the above makes sence , can I have multiple layers - like the first for the background , the second for the "bottom" objects and so on - then sort of
super-compose one in top of the other???
Please give me detailed solutions (with some code if possible ) It ' s not like I have no idea how to do it , I just want to know how to get things faster...
Thanks!!!

Answer 1

When you repaint a shape, user repaint(myShape.getBounds()). In the paint-method, use these bounds to draw a subimage off a BufferedImage. Oh, and before drawing the subimage, do this:
Vector myShapes = ...;
for(int i = 0; i < myShapes.size(); i++) {
if(((Shape)myShapes.elementAt(i)).getBounds().intersects(myRectangle))
((Graphics2D).fill(((Shape)myShapes.elementAt(i));
myShapes = a Vector containing all the shapes.
myRectangle = the the bounds of the shape in need of repaint.
Now this is as optimized as it gets: It paints a small part of the screen, it paints only the shapes needed, and it only paints a small part of the BufferedImage. If you need movement, though, you might have to work a bit on this.
Nille