JPanel is "Tearing" / Jerky

I used a CardLayout to put two JPanels on top of another for my application.
The first jpanel is of my game, which runs perfectly fine without slowdowns.
On the title screen, however, I am noticing some tearing and I can’t for the life of me figure out why.
The code (as far as I can see) is pretty much almost the same as the game’s in terms of structure.
The moving “FakeBlocks” tear occasionally and the animation is jerky (unlike in the game – which works perfectly).

Does it look like I’m missing an override, or as if I’m skipping / calling the wrong thing?
I’ve been looking at this code for a few hours now.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.ArrayList;
import java.util.*;
import java.io.*;


public class LevelSelect extends JPanel implements MouseMotionListener,MouseListener {
	public static Image bufferImage;
	public Image background = Toolkit.getDefaultToolkit().getImage("images/misc/background1.png");
	public Game GamePanel = new Game();
	public int ctr;
	private ArrayList a = new ArrayList();
	Random rnd = new Random();
	FontMetrics fm;
	Font cookies;
	AnimUpdate update;
	public LevelSelect() {
		setDoubleBuffered(false);
		setIgnoreRepaint(true);
		rnd.setSeed(System.currentTimeMillis());
		setLayout(new GridLayout());
		addMouseListener(this);
		addMouseMotionListener(this);
		add(GamePanel);
		GamePanel.setSize(this.getWidth(),this.getHeight());
		GamePanel.setVisible(false);
		cookies = GameScreens.cookies.deriveFont((float)24);
		fm = getFontMetrics(cookies);
		for (int i=0; i<1; i++) {
			FakeBlock fb = new FakeBlock();
			fb.blockType=rnd.nextInt(8)+1;
			fb.speed=(rnd.nextInt(4)+2)*2;
			fb.xPos=rnd.nextInt(481);
			fb.yPos=15+i*65;//112+i*35;
			fb.setImage();
			a.add(fb);
		}
		
		update = new AnimUpdate();
		update.start();
		setVisible(true);
	}	
	
	public void paintComponent(Graphics g) {
		Graphics2D g2;
		
		// Create bufferImage & set vars if it/they don't exist
		if (bufferImage == null) {
			bufferImage = createImage(this.getWidth(),this.getHeight());			
			g2 = (Graphics2D)bufferImage.getGraphics();
			g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
		}
		
		g2 = (Graphics2D)bufferImage.getGraphics();
		g2.setFont(cookies);

		String str2 = "Click to Continue";
		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
		
		g2.drawImage(GameScreens.background,0,0,null);
		AlphaComposite ac;
		ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER,(float).4);
		g2.setComposite(ac);
		for (int i=0; i<a.size(); i++) {
			FakeBlock fb = (FakeBlock)a.get(i);
			fb.move();
			g2.drawImage(fb.myPicture,fb.xPos,fb.yPos,null);
		}
		ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER,(float)1);
		g2.setComposite(ac);
		g2.drawImage(GameScreens.titleScr,0,0,null);
		
		ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER,(float)Math.abs(Math.sin(Math.toRadians(ctr%180))));
		g2.setComposite(ac);
		g2.drawString(str2,(int)((this.getWidth()-fm.stringWidth(str2))/2.0),320);
		g.drawImage(bufferImage,0,0,null);
	}
	
    public void update(Graphics g) {
    	paintImmediately(0,0,480,400);
    }
	
	public void paint(Graphics g) {
		paintComponent(g);
	}
		public void mouseDragged(MouseEvent e) {
	} //end method mouseDragged
	
	//for when the mouse is just moving
	public void mouseMoved(MouseEvent e) {
	} //end of method mouseMoved
	
	//for when the mouse button is held down
	public void mousePressed(MouseEvent e) {
	} //end of method mousePressed
	
	//for when the mouse button is released
	public void mouseReleased(MouseEvent e) {
		GameScreens.goGameScreen();
	} //end of method mouseReleased
	
	//some unused mouse methods
	public void mouseClicked(MouseEvent e) {
	}
	public void mouseEntered(MouseEvent e){ }
	public void mouseExited(MouseEvent e) { }
	
	class FakeBlock {
		public int blockType;
		public AlphaComposite alpha;
		public int xPos;
		public int yPos;
		public double speed;
		public double alphaOffset;
		public double alphaSpeed;
		public Image myPicture;
		
		public FakeBlock() {
			
		}
		
		public void setImage() {

			if (blockType == 0) {
				myPicture=GameScreens.one;
			} else if(blockType ==1) {
				myPicture=GameScreens.two;
			} else if (blockType == 2) {
				myPicture=GameScreens.thr;
			} else if (blockType == 3) {
				myPicture=GameScreens.fou;
			} else if(blockType == 4) {
				myPicture=GameScreens.fiv;
			} else if (blockType == 5) {
				myPicture=GameScreens.six;
			} else if (blockType == 6) {
				myPicture=GameScreens.sev;
			} else if (blockType == 7) {
				myPicture=GameScreens.eig;
			} else if (blockType == 8) {
				myPicture=GameScreens.nin;
			}
		}
		
		public void paint(Graphics g) {
			paintComponent(g);
		}
		
		public void move() {
			xPos += (int)speed;
			if (xPos > 481) {
				blockType=rnd.nextInt(8)+1;
				speed=(rnd.nextInt(4)+2)*2;
				xPos=-32-rnd.nextInt(200);

				setImage();
			}
		}
	}
	
	class AnimUpdate extends Thread {
		//the method run when .start() is called
		public void run() {
			while(Thread.currentThread() == update) {
				//paint & update the frame number
				paintImmediately(0,0,480,400);
				++ctr;
				try { //sleep try-catch
					Thread.sleep(16);	
				} catch(InterruptedException e) {
					System.out.println("InterruptedException @ AnimUpdate");
				} //end of try-catch block (sleep)
				
				
			} //end of while loop
		} //end of run() method
	} //end of class AnimUpdate
}
  1. I believe paintImmediately() skips the double buffering and paints directly to the screen. (Can someone confirm this?) You should use “repaint()” instead.

  2. You’ll get much better results if you use BufferStrategy instead of calling for constant repaints. Repaint() used to be the only solution for active rendering, but it was always inefficient. The BufferStrategy APIs, OTOH, give you direct access to the underlying DirectDraw/OpenGL pipelines for h9igh-performance rendering.

Yes, jbanes is most likely right about paintImmediately.

You are modifying the perspective or positions of entities from one thread while another thread is painting. There are two options AFAI can see:

  1. do everything from the event dispatch thread.
  2. do nothing from the event dispatch thread (you’ll have to queue e.g. keyboard or mouse input which is otherwise managed from the event dispatch thread so you can handle it elsewhere).