Thread: paintComponent() instead of paint()

(sorry, previously posted in wrong topic)

OK, I am, as a programming rite, programming my own little version of conway's game of life, and it works fine, apart from trying to paint. I previously used the Paint method, which worked fine. This however, I have been told, is an inefficient way of doing this, so I tried to rearrange the code to use paintComponent(). This is the output that should have been produced, (and was produced using paint()):



Now, I have moved the paintComponent method out of the main swing class and into a separate one that extends JPanel. I apologise for the messiness of my layout code, I was rearranging everything to see whether it was in the right order :/

The grid of squares does not draw at all.

(I have not included the game code, but I run the GUI with InvokeLater.)

Main swing code(I have left out the other methods-yes i deleted the paint() method entirely):

(scroll down halfway and you will see my comment as I add the drawing.

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SpringLayout;
import javax.swing.SwingUtilities;
 
 
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.geom.*;
 
public class GUI extends JFrame implements MouseListener, ComponentListener{
 
	Game gam = new Game();
 
	JPanel mainPanel = new JPanel();
	JPanel gPanel = new JPanel();
	JPanel iPanel = new JPanel();
    JLabel Gen = new JLabel("Generation: " + gam.getGen());
    JLabel FPS = new JLabel("FPS: ");
 
 
 
	public GUI(){
		initUI();
	}
 
	public final void initUI(){
 
 
 
 
		SpringLayout layout = new SpringLayout();
		SpringLayout gLayout = new SpringLayout();
 
		setTitle("Game Of Life");
	    setSize(620, 750);
	    setLocationRelativeTo(null);
	    setDefaultCloseOperation(EXIT_ON_CLOSE);
 
 
	    setLayout(null);
 
		getContentPane().add(iPanel);
		getContentPane().add(gPanel);
 
 
		gPanel.setBounds(0, 0, getWidth(), (getHeight()/6)*5);
		iPanel.setBounds(0, (getHeight()/6)*5, getWidth(), getHeight()/6);
 
		gPanel.setLayout(gLayout);
		iPanel.setLayout(layout);
 
		addComponentListener(this);
		gPanel.addMouseListener(this);
 
 
 
	    gPanel.setOpaque(true);
 
 
 
	    //---------------------------- ADDING THE drawComponent class ------------------------------------------------------
	    GridDraw drawG = new GridDraw();
		gPanel.add(drawG);
		gPanel.repaint();
 
		gLayout.putConstraint(SpringLayout.NORTH, drawG, 20, SpringLayout.NORTH, gPanel);
		gLayout.putConstraint(SpringLayout.EAST, drawG, 10, SpringLayout.EAST, gPanel);
 
 
 
	       JButton PButton = new JButton("Pause");
 
 
	       layout.putConstraint(SpringLayout.HORIZONTAL_CENTER, PButton, 0, SpringLayout.HORIZONTAL_CENTER, iPanel);
	       layout.putConstraint(SpringLayout.NORTH, Gen, 2, SpringLayout.NORTH, iPanel);
	       layout.putConstraint(SpringLayout.WEST, Gen, 0, SpringLayout.WEST, iPanel);
	       layout.putConstraint(SpringLayout.NORTH, FPS, 2, SpringLayout.SOUTH, Gen);
 
 
	       PButton.addActionListener(new ActionListener() {
	           public void actionPerformed(ActionEvent event) {
	        	   gam.pause();
	        	   repaint();
	          }
	       });
 
 
 
		iPanel.add(PButton);
		iPanel.add(Gen);
		iPanel.add(FPS);
		getRootPane().setDefaultButton(PButton);
		gPanel.setVisible(true);
 
 
 
	}

and the PaintComponent code(much more palatable, but still unorganised at the moment):

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
 
import javax.swing.JPanel;
 
public class GridDraw extends JPanel{
 
 
	Graphics g;
 
 
	Game gam = new Game();
//	GUI gui = new GUI();
 
 
 
	@Override
	public void paintComponent(Graphics g){
 
//			super.paintComponent(g);
 
		Graphics2D g2 = (Graphics2D)g;
 
		boolean[][] grid = gam.getGrid();
		int gWidth = gam.getWidth();
		int gHeight = gam.getHeight();
 
 
//		gui.printGen();
 
		for(int i=1; i < gHeight+1; i++){
			for(int j=1; j < gWidth+1; j++){ //selecting an individual cell
				if(grid[j][i] == true){
					g2.setColor(Color.green);
					g2.fillRect(j*5 + j + 5, i*5 + i + 26, 5, 5);
					//on					
				}
				else{
					g2.setColor(Color.black);
					g2.fillRect(j*5 + j + 5, i*5 + i + 26, 5, 5);
					//off
				}
			}						
		}	
	}
 
 
}

Now everything shows up apart from the drawing drawn with the paintcomponent method. I have been googling for hours, but i can't understand why.

Thank you.