Graphics flickering

Newbie & Debugging Questions
#1

Hello,

Im quite new to java programmming, but i made a dos tetris game about 10 years ago with c++ so i know some programming.

Im currently making my first javagame. It needs 2d graphics so im using graphics 2d. I understand it makes a doublebuffer but my graphics are still flickering.

I get no flickering on the graphics that are not moving. But moving my players on the field makes them flicker a bit. And if I try to use g.drawString(player.name,player.x,player.y); to show the players name under the player while he is moving, the text flickers like mad.

My game runs in windowed mode.

So, any ideas why my doublebuffered game graphics are flickering?

#2

Well probably you’re not buffering it right :slight_smile:

create an offscreen image . render your scene to its Graphics2D - that is , everything . background, characters, and stuff .
Only after completing the above step , draw the offscreen Image to the screen. That’s just about it .

#3

We’d need to know more about how you’re using the double buffering.

#4

Huh,

I searched for lots of tutorials about this and they only made it worse.

I finally found this one which is almost the same as my original code.

http://www.idevgames.com/forum/showthread.php?t=5301 near the bottom is an example code and it makes the text flicker like it did before, but the game runs fine.

I tried other ways also, where i used Buffered offscreen image and it caused the game to slow down very dramatically. And it didnt even look like doublebuffered. The text was flickering but very slowly.

#5

post your code then, so we can take a look

#6

Obviously posting what you actually have will result in more direct feedback, but this could also be a good place to start: http://fivedots.coe.psu.ac.th/~ad/jg/ch1/ch1.pdf It’s about creating a animation loop and displaying your game in a Swing component, which seems to be what you’re trying to do.

#7

Theres some of the code. Its based on coke and coke Space invaders tutorial. I couldnt post it all. Theres a 10000 character limit…

public class ThegameFrame extends Canvas implements MouseListener {

/** The stragey that allows us to use accelerate page flipping */
private BufferStrategy strategy;

public ThegameFrame() {

 	JFrame container = new JFrame("Death Match");
	
	// get hold the content of the frame and set up the resolution of the game
	JPanel panel = (JPanel) container.getContentPane();
	panel.setPreferredSize(new Dimension(1024,768));
	panel.setLayout(null);
	
	// setup our canvas size and put it into the content of the frame
	setBounds(0,0,1024,768);
	panel.add(this);
	
    addMouseListener(this);

// finally make the window visible
container.pack();
container.setResizable(false);
container.setVisible(true);

	setIgnoreRepaint(true);
	container.setIgnoreRepaint(true);
	panel.setIgnoreRepaint(true);
	
	
	//Setting up Double Buffering
	createBufferStrategy(2);
	BufferStrategy strategy = getBufferStrategy();
	
	// add a listener to respond to the user closing the window. If they
	// do we'd like to exit the game
	container.addWindowListener(new WindowAdapter() {
		public void windowClosing(WindowEvent e) {
			System.exit(0);
				}
	});

public void gameLoop()
{
long lastLoopTime = System.currentTimeMillis();
// long animtimer = System.currentTimeMillis();
// long delta = System.currentTimeMillis();

	Random generator = new Random();

while (matchon)
{

		// work out how long its been since the last update, this
		// will be used to calculate how far the entities should
		// move this loop
		long delta = System.currentTimeMillis() - lastLoopTime;
		lastLoopTime = System.currentTimeMillis();
		
		
		if (strategy == null)	{
			createBufferStrategy(2);
			strategy = getBufferStrategy();
		}

		// Get hold of a graphics context for the accelerated 
		// surface and blank it out

		Graphics g = null;
		g = strategy.getDrawGraphics();

		g.setColor(Color.white);
//		g.fillRect(0,0,1024,768);
		g.fillRect(0,0,1024,200);
		g.fillRect(0,570,1024,198);
		

                       LOTS OF DRAWING AND COUNTING HERE

g.dispose();

// drawScreen();
if (!strategy.contentsLost()) {
strategy.show();
Toolkit.getDefaultToolkit().sync();
}

		// finally pause for a bit. Note: this should run us at about
		// 100 fps but on windows this might vary each loop due to
		// a bad implementation of timer
		try { Thread.sleep(10); } catch (Exception e) {}
	}
}
#8

Hello

Here is a template I use for creating my game. It’s very simple

ackage basicGame;

import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.image.BufferStrategy;

import javax.swing.JFrame;
import javax.swing.JPanel;


public class Game implements Runnable{
	
	final int WIDTH = 1000;
	final int HEIGHT = 700;
	
	JFrame frame;
	Canvas canvas;
	BufferStrategy bufferStrategy;
	
	public Game(){
		frame = new JFrame("Basic Game");
		
		JPanel panel = (JPanel) frame.getContentPane();
		panel.setPreferredSize(new Dimension(WIDTH, HEIGHT));
		panel.setLayout(null);
		
		canvas = new Canvas();
		canvas.setBounds(0, 0, WIDTH, HEIGHT);
		
		panel.add(canvas);
		
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.pack();
		frame.setResizable(false);
		frame.setVisible(true);
		
		canvas.createBufferStrategy(2);
		bufferStrategy = canvas.getBufferStrategy();
		
		canvas.requestFocus();
		canvas.addMouseListener(new MouseControl());
	}
	
	private class MouseControl extends MouseAdapter{
		
	}
	
	long desiredFPS = 60;
    long desiredDeltaLoop = (1000*1000*1000)/desiredFPS;
    
    long desiredDeltaUpdate = 10;
    
	boolean running = true;
	
	public void run(){
		
		long beginLoopTime;
		long endLoopTime;
		long currentUpdateTime = System.nanoTime();
		long lastUpdateTime;
		long deltaLoop;
		
		while(running){
			beginLoopTime = System.nanoTime();
			
			render();
			
			lastUpdateTime = currentUpdateTime;
			currentUpdateTime = System.nanoTime();
			update((int) ((currentUpdateTime - lastUpdateTime)/(1000*1000)));
			
			endLoopTime = System.nanoTime();
			deltaLoop = endLoopTime - beginLoopTime;
	        
	        if(deltaLoop > desiredDeltaLoop){
	            //Do nothing. We are already late
	        }else{
	            try{
	                Thread.sleep((desiredDeltaLoop - deltaLoop)/(1000*1000));
	            }catch(InterruptedException e){
	                //Do nothing
	            }
	        }
		}
	}
	
	protected void render() {
		Graphics2D g = (Graphics2D) bufferStrategy.getDrawGraphics();
		g.clearRect(0, 0, WIDTH, HEIGHT);
		//Drawing code here
		g.dispose();
		bufferStrategy.show();
	}

	protected void update(int deltaTime) {
		//Update code here
	}
	
	public static void main(String [] args){
		Game ex = new Game();
		new Thread(ex).start();
	}

}
#9

Caused no issues for me, but it’s probably caused by the frame re-painting itself automatically. You need to disable this when using active rendering using the ‘setIgnoreRepaint’ method. Second; you should also do all of the setup code before calling pack and setVisible. Typically those calls should always be last. Some code is automatically run by the classes behind the scenes which connects the frame to the display by those methods, and it’s caused issues for me in the past.

My constructor for your code is:

public Game(){
		frame = new JFrame("Basic Game");
                frame.setIgnoreRepaint( true );
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		canvas = new Canvas();
		canvas.setBounds(0, 0, WIDTH, HEIGHT);
                canvas.setIgnoreRepaint(true);
		canvas.createBufferStrategy(2);
		canvas.addMouseListener(new MouseControl());
                
		bufferStrategy = canvas.getBufferStrategy();
                
		JPanel panel = (JPanel) frame.getContentPane();
		panel.setPreferredSize(new Dimension(WIDTH, HEIGHT));
		panel.setLayout(null);
		panel.add(canvas);
                
		frame.pack();
		frame.setResizable(false);
		frame.setVisible(true);
		canvas.requestFocus();
	}
#10

I tried to use your constructor code.

I had to move the buferstategy codes to last, because they caused the game to crash. It said something like “component must have a valid peer”.

Now the game behaves like it did before.

I draw black text and background that dont move. Those look great. The players on the field are ok. I think they flicker a bit. Not much. But the white text under the ball carrying player that indicates his name flickers like mad.

	if ( ball.state == 1 || ball.state == 2 )
			{				
				g.setColor(Color.white);
				g.drawString(messageballcarrier,(int)ball.x -20,(int)ball.y + 20);
			}

I started to think that maybe I am doing doublebuffermode ok, but the ball.x double to int coordinate conversion could make some flickering kind of effect?

My current constructor code:

public ThegameFrame() {
		
	JFrame frame = new JFrame("Death Match Manager");
    frame.setIgnoreRepaint( true );
	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

	Canvas canvas = new Canvas();
	canvas.setBounds(0, 0, 1024, 768);
    canvas.setIgnoreRepaint(true);

// canvas.createBufferStrategy(2);
// canvas.addMouseListener(new MouseControl());

    canvas.addMouseListener(this);     
    canvas.addKeyListener(new KeyInputHandler());

// strategy = canvas.getBufferStrategy();

	JPanel panel = (JPanel) frame.getContentPane();
	panel.setPreferredSize(new Dimension(1024, 768));
	panel.setLayout(null);
	panel.add(canvas);
	
	
            
	frame.pack();
	frame.setResizable(false);
	frame.setVisible(true);
	panel.setVisible(true);
	canvas.setVisible(true);
	canvas.requestFocus();

// nämä piti siirtää setvisiblen alle
canvas.createBufferStrategy(2);
strategy = canvas.getBufferStrategy();

 	//OMAAA
 	gamestate = 1;	// 1 = Setup phase, 2 = Game on,

// score1 = 0;
// score2 = 0;
matchon = true;

 	for ( int i = 0; i < 8; i++)
			message[i] = " ";
	
	
	// add a key input system (defined below) to our canvas
	// so we can respond to key pressed
	
	
	// request the focus so key events come to us

// requestFocus();

	Random generator = new Random();
	
	// ALUSTETAAN DEBUGGAUS JOUKKUEET
	
	Player player = new Player(this,"ogrelay.png",370,350,1);
	player.makeOgre();
	player.name = "Ogre dude";
	entities.add(player);
	
	for ( int i = 0; i < 9; i++)
	{
		player = new Player(this,"lay.png",generator.nextInt(300),generator.nextInt(768),1);
	 	player.makeHuman();
		entities.add(player);
		player.name = "Lineman dude";
		if ( i == 6)
		{
			player.name = "Wing dude";
			player.position = 3;	//WING
		}
		if ( i == 5)
		{
			player.name = "Thrower dude";
			player.position = 2;	//THrower
		}
	}
	player.name = "Wing dude 2";
	player.position = 3;	//WING
	
	for ( int i = 0; i < 10; i++)
	{
		player = new Player(this,"xlay.png",(generator.nextInt(300)+700),generator.nextInt(768),2);
	 	player.makeHuman();
		entities.add(player);
		player.name = "Lineman dude";
		if ( i == 6)
		{
			player.name = "Wing dude";
			player.position = 3;	//WING
		}
		if ( i == 5)
		{
			player.name = "Thrower dude";
			player.position = 2;	//THrower
		}
	}
	player.name = "Wing dude 2";
	player.position = 3;	//WING

// container.setIgnoreRepaint(true);
// panel.setIgnoreRepaint(true);

	}
#11

Im starting to find the problem :smiley:

The doublebuffering is working ok, im quite sure, and allways was working.

I tried to draw every players name under them and it worked ok :smiley: no flickering.

There must be some bug in the codes between the ball and the player carrying it, that causes it not to draw the text every cycle.

Well, thanks for your help anyways :smiley:

status = feeling dumb;

#12

Hello,

I agree with you for the setIgnoreRepaint (still it doesn’t change a lot but it’s better to have it)

But your second point is half wrong. You absolutely need to make your frame visible before doing createBufferStrategy(2) or it will cause an error. But I could have put the mouseListener before making it visible.