Question

I’m working on making a board game for chess and checkers (and a few variations that I want to make). I’ve got a Board class that extends JPanel and sets up a doubly dimensioned array of JPanels to act as my board. Here’s some of the code for my board class:

public class Board extends JPanel {

  private static final int COLS = 8;
  private static final int ROWS = 8;

  private JPanel[][] board = new JPanel[COLS][ROWS];
  private JPanel chessBoard;

  public Board() {
    super();
    super.setLayout(new BorderLayout());

    chessBoard = new JPanel();
    chessBoard.setLayout(new GridLayout(COLS,ROWS));

    // Set up JPanels on bottom and right to display letters and numbers for the board
    // JPanels are called south and west
    super.add(chessBoard, BorderLayout.CENTER);
    super.add(south, BorderLayout.SOUTH);
    super.add(west, BorderLayout.WEST);

    for (int i=0; i<COLS; i++) {
      for (int j=0; j<ROWS; j++) {
        // Set up the grid
        board[i][j] = new JPanel();
        board[i][j].setBackground(getColor(i,j));
        chessBoard.add(board[i][j]);
      }
    }
    super.validate();
  }

  private Color getColor(int x, int y) {
    if ((x + y) % 2 == 0) {
      return Constants.GOLD;
    } else {
      return Constants.PURPLE;
    }
  }

  public void addPiece(Piece piece) {
    JLabel p = piece.getImage();

    board[piece.getX()][piece.getY()].add(p);
    chessBoard.validate();
  }
}

Piece is an interface that that I’m going to use for all my pieces. I’ve set up the interface and set up one class that implements the interface (Checker class). I have all of that set up. The pieces are JLabels with ImageIcons in them. The only problem I’m having so far is writing a move method. I can figure out the logic make sure a move is a valid one, I just don’t know how to actually make the move happen.

EDIT: I’m not even asking about mouse listeners or anything like that, I just want some pseudocode to explain making a piece move from one spot in the array to another.

EDIT 2: Here’s the code for my Checkers class.

public class Checker implements Piece {
  private int side,xPos,yPos; 
  private JLabel img;

  public Checker(int team, int x, int y) {
    BufferedImage image;

    try {
      if (team == 0)
        image = ImageIO.read(new File("img/RedPiece.png"));
      else
        image = ImageIO.read(new File("img/BlackPiece.png"));
    } catch(IOException e) {
      image = null;
      System.out.printf("Image file wasn't found!!!");
      System.exit(1);
    }

    img = new JLabel(new ImageIcon(image), SwingConstants.CENTER);
    img.setVerticalAlignment(SwingConstants.CENTER);

    xPos = x;
    yPos = y;
  }

  // TODO Figure out move method
  public void move(int dx, int dy) {

  }

  // Also typical gets and sets for instance variables

So my thought is I call the move method for a checkers piece and, assuming I’m moving from the bottom of the screen to the top it would be piece.move(-1,1); and I have to remove the piece from it’s current position, then it’s new position in the array is [x + dx][y + dy]

Answer 1

Can you use something like this:

public void movePiece(Piece piece, int dx, int dy) {
  // Save current position, so we can erase the piece.
  int oldX = piece.getX();
  int oldY = piece.getY();

  // Update the location.
  piece.setX(oldX + dx);
  piece.setY(oldY + dy);

  // Remove piece from old position
  board[oldX][oldY].clear();

  // Add it to the new position.
  addPiece(piece);
}

You’d probably want to use a Point instead of individual x and y coordinates; I just thought this would be easier to understand.