Swing graphics in multithreaded program

Question

I'm coding a game; something like this: http://i.stack.imgur.com/HBrEE.png

I have a class named Canvas which extends JLabel and in overriden paintComponent() , put an image of gridlines as background, then paint the player and obstacles (walls).

By using createGraphics() , I get a Graphics2D object. I need this to paint weapons and bullets from their classes, too. (As you see, there are several weapons that shoot bullets in specific time intervals.)

For implementing all these, using SwingUtilities.invokeLater() I paint the gridlines, player and walls in Canvas class. I thought of creating a thread per weapon and one per bullet; I know, it's an overkill but since I'm new to multithreading I have no other ideas!

And another problem is with Graphics2D object: I need to share this object between threads so I thought of using final keyword; but it's not possible because the value of Graphics2D object will be determined in paintComponent() .

Thanks in advance for any help you are able to provide.

Answer 1

You shouldn't use multi-threaded rendering threads ever (well, in 99% of the cases at least). Most graphics programs keep the full scene state in some object tree that only one thread renders every so often (1/60th of a second). The rendering thread goes through each object in the render tree and invoke .paint or whatever else will get the object to be drawn. Rinse and repeat and you're done.