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.