displaying problem

[Savanna Ray]

Hi,

I'm trying to display a 3X3 grid for a tictactoe game, here's the code so far:

import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;
 
public class Lab11 extends Applet implements MouseListener {
 
    private Board tictac;
 
    public void init() {
 
        tictac = new Board(3, 3);
        this.addMouseListener(this);
    }
 
    public void mouseClicked(MouseEvent e) {
 
         e.getX();
         e.getY();
    }
 
    public void  mouseReleased(MouseEvent e) {
    }
 
    public void  mousePressed(MouseEvent e) {
    }
 
    public void  mouseEntered(MouseEvent e) {
    }
 
    public void  mouseExited(MouseEvent e) {
    }
}
 
class Board {
 
    private Cell[][] board;
    private int rowIndex;
    private int colIndex;
    private int cellSize = 50;
    private final int xStart = 100;
    private final int yStart = 70;
 
    private int sum;
 

    public Board(int rows, int columns) {
 
        Cell[][] board = new Cell[rows][columns];
        for(int row = 0; row < board.length; row++) {
            for(int col = 0; col < board[0].length; col++) {
                board[row][col] = new Cell(xStart + col * cellSize, yStart + row * cellSize, cellSize);
            }
        }
    }
 
    public void display(Graphics g) {
 
        for(int row = 0; row < board.length; row++) {
            for(int col = 0; col < board[0].length; col++) {
                board[row][col].draw(g);
            }
        }
    }
}
 
class Cell {
 
    private int x;
    private int y;
    private int cellSize;
    private String contents;
 
    public Cell(int x, int y, int size) {
 
        this.x = x;
        this.y = y;
        this.cellSize = cellSize;
 
    }
 
    public void draw(Graphics g) {
 
        g.drawRect(x, y, cellSize, cellSize);
    }
}

This program actually compiles, but for some reason it won't display anything when I run the program? Any help would be appreciated. Thanks.

Savanna

[Ernest Friedman-Hill]

There's nothing here that will ever call "display()". You could override the paint(Graphics) method of Applet and call it there:

public void paint(Graphics g) {
  tictac.display(g);
}

That will get you started.

The next problem you're likely to face is that the dimensions of the board aren't based on those of the applet, so probably you'll only see part of the board. Instead of the sizes being fixed in Board, the Board should get the sizes from the applet, either as constructor arguments, or by being made into a Component itself, added to the applet, which would have its own coordinates.

[Savanna Ray]

Thanks for replying, Ernest!

I tried adding the paint method, tictac.display(g), but nothing appeared on the display. The "dos" window shows a 'NullPointerException' at Board.display line 63. Maybe there's a problem in passing the values to the draw method?