BufferStrategy - it doesn't update graphics

Newbie & Debugging Questions
#1

Hi, I’m having problems with BufferStrategy… for some reason I can’t manage to update the graphics in it:

public void Draw()
    {
        backbuffer = this.getBufferStrategy();
        
        do 
        {
            try{
                    graphics = backbuffer.getDrawGraphics();
                    DrawAll(); //this draws thing on "graphics"
            }
            finally
            {
                graphics.dispose();
            }

            backbuffer.show();
            Toolkit.getDefaultToolkit().sync();
        } while (backbuffer.contentsLost());
    }

It is necessary to say that I always call this method? but for some reason I can’t see my … new graphics?
If you need more details, just tell me.

Thanks.

#2

We’re probably gonna need to see more code to provide much useful help, for instance the DrawAll() method, and how/when things are initiated would be useful.

First, although I don’t think it should make a difference (could be wrong, it’s been awhile), I would dispose the graphics after backbuffer.show(), as per http://docs.oracle.com/javase/tutorial/extra/fullscreen/bufferstrategy.html

#3

the only way I actually managed to “correctly” update the drawing, is by drawing something over it, using:

graphics.setColor (getBackground ());
graphics.fillRect (0, 0, this.getSize().width, this.getSize().height);

but, isn’t

graphics.dispose();

supposed to clear the graphics and let space for the incoming?

thanks

#4

No. Graphics.dispose() basically destroys that particular graphics context, and any calls to it after are ignored.

Also, instead of setting the current color to the background color and fillRect, you can simply: clearRect()
That uses the background color (hence ‘clear’ as in wipe off) automatically.

#5

[quote]First, although I don’t think it should make a difference (could be wrong, it’s been awhile), I would dispose the graphics after backbuffer.show(), as per http://docs.oracle.com/javase/tutorial/extra/fullscreen/bufferstrategy.html
[/quote]
this link dispose the graphics before showing them from backbuffer

good tip

#6

Quick working example usage of BufferStrategy:


import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;

public class BSTest {
	
	public static void main(String[] a) throws InterruptedException {
		JFrame frame = new JFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(400, 400);
		frame.setVisible(true);
		frame.setLocationRelativeTo(null);
		
		frame.createBufferStrategy(2);
		
		while (true) {
			Graphics g = null;
			t: try {
				g = frame.getBufferStrategy().getDrawGraphics();
				if (g == null) break t;
				render(g);
			} finally {
				g.dispose();
			}
			frame.getBufferStrategy().show();
			Thread.sleep(20);
		}
	}
	
	private static void render(Graphics g) {
		g.clearRect(0, 0, 400, 400);
		g.setColor(Color.blue);
		g.fillOval((int) System.currentTimeMillis() % 400, (int) System.currentTimeMillis() % 400, 10, 10);
	}
}

This works fine for me, take from it what you will.

#7

Thanks, looks pretty similar to my approach, but I think that what does the trick is

    g.clearRect(0, 0, 400, 400);
      g.setColor(Color.blue);

so, Solved!