问为什么我的棋盘不出现？用java创建游戏

EN

CheckerBoard content = new CheckerBoard(); // Sets the CheckerBoard values into the content to be used in the next line
        application.setContentPane(content); // Container holds the values together, Content pane of the CheckerBoard
        application.pack();  // Use preferred size of content to set size of application.
        Dimension screensize = Toolkit.getDefaultToolkit().getScreenSize();
        application.setLocation( (screensize.width - application.getWidth())/2,
                (screensize.height - application.getHeight())/2 );
        application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); // Sets so that the application can be exited when the application is closed
        application.setResizable(false);  // This makes it so that the user can't change the application's size.
        application.setVisible(true); // Sets it so that the application can actually be seen

public CheckerBoard()  {
// This is going to be a constructor, this constructor will set the layout manager for the panel to be null, it will then add components to the panel
// and it will set their bounds.

    setLayout(null);  // So that it will match my requirement specification, I will do the layout myself
    setBackground(new Color(0,120,0));  // Dark Green Background colour.
    setPreferredSize(new Dimension(350,250)); // The size of the Panel

    BoardComplete checkerboardData = new BoardComplete();
    add(checkerboardData); // This will create the components and add them to the content pane
    add(NewGameButton);
    add(ResignButton);
    add(MessageDisplay);

 // I will now have to produce a method to set the position and size of each component by calling its setBounds() method
    checkerboardData.setBounds(20,20,164,164); // Sets the board dimensions
    NewGameButton.setBounds(210, 60, 120, 30); 
    ResignButton.setBounds(210, 120, 120, 30); 
    MessageDisplay.setBounds(20, 200, 350, 30); 
    }   

 BoardComplete() {
        setBackground(Color.BLACK);
        addMouseListener(this);
        ResignButton = new JButton("Resign");
        ResignButton.addActionListener(this);
        NewGameButton = new JButton("New Game");
        NewGameButton.addActionListener(this);
        MessageDisplay = new JLabel("",JLabel.CENTER);
        MessageDisplay.setFont(new  Font("Serif", Font.BOLD, 14));
        MessageDisplay.setForeground(Color.green);
        checkerboardData = new DataForCheckers();
        MakeaNewGame();
    }       

    public void PaintCheckerBoard(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        // This will draw a two-pixel black border around the edges of the canvas. 

        g.setColor(Color.black);
        g.drawRect(0,0,getSize().width-1,getSize().height-1);
        g.drawRect(1,1,getSize().width-3,getSize().height-3);

        // Draw the squares of the checkerboard and the checkers.

        for (int row = 0; row < 8; row++) {
            for (int col = 0; col < 8; col++) {
                if ( row % 2 == col % 2 )
                    g.setColor(Color.LIGHT_GRAY);
                else
                    g.setColor(Color.GRAY);
                g.fillRect(2 + col*20, 2 + row*20, 20, 20);
                switch (checkerboardData.PieceLocation(row,col)) {
                case DataForCheckers.RED:
                    g.setColor(Color.RED);
                    g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                    break;
                case DataForCheckers.BLACK:
                    g.setColor(Color.BLACK);
                    g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                    break;
                case DataForCheckers.RED_KING:
                    g.setColor(Color.RED);
                    g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                    g.setColor(Color.WHITE);
                    g.drawString("K", 7 + col*20, 16 + row*20);
                    break;
                case DataForCheckers.BLACK_KING:
                    g.setColor(Color.BLACK);
                    g.fillOval(4 + col*20, 4 + row*20, 15, 15);
                    g.setColor(Color.WHITE);
                    g.drawString("K", 7 + col*20, 16 + row*20);
                    break;
                }
            }
        }

        // If there is a game in progress, highlight the legal moves that the player can make.
        // It can be seen that in this process, LegalMoves is never null while a game is in progress     

        if (CheckerMatchInProgress) {
            /* First, draw a 2-pixel cyan border around the pieces that can be moved. */
            g.setColor(Color.cyan);
            for (int i = 0; i < LegalMoves.length; i++) {
                g.drawRect(2 + LegalMoves[i].fromCol*20, 2 + LegalMoves[i].fromRow*20, 19, 19);
                g.drawRect(3 + LegalMoves[i].fromCol*20, 3 + LegalMoves[i].fromRow*20, 17, 17);
            }
            // If a piece is selected to be moved, for example if ChosenRow>=0, then
            // draw a 2-pixel white border around that piece, and draw a green border
            // around each square that the piece can be legally moved to.

            if (ChosenRow >= 0) {
                g.setColor(Color.white);
                g.drawRect(2 + ChosenColumn*20, 2 + ChosenRow*20, 19, 19);
                g.drawRect(3 + ChosenColumn*20, 3 + ChosenRow*20, 17, 17);
                g.setColor(Color.green);
                for (int i = 0; i < LegalMoves.length; i++) {
                    if (LegalMoves[i].fromCol == ChosenColumn && LegalMoves[i].fromRow == ChosenRow) {
                        g.drawRect(2 + LegalMoves[i].toCol*20, 2 + LegalMoves[i].toRow*20, 19, 19);
                        g.drawRect(3 + LegalMoves[i].toCol*20, 3 + LegalMoves[i].toRow*20, 17, 17);
                    }
                }
            }
        }

    }  // end PaintCheckerBoard()