java - Tic Tac Toe 游戏 - 数组没有保存值(value)？

Question

我正在创建一个 Tic Tac Toe 游戏(带有 GUI)，并且使用 2D 数组来确定获胜者。我发现当用户单击板上的某个位置后，数组不会保存以前的值。

所以如果 board[0][0] 是“X”，则数组是

[[X, 2, 3], [4, 5, 6], [7, 8, 9]]

之后，如果用户点击 board[1][1]，则数组应为:

[[X, 2, 3], [4, X, 6], [7, 8, 9]]

但它是:

[[1, 2, 3], [4, X, 6], [7, 8, 9]]

为什么会发生这种情况？

这是代码:

private class Play implements ActionListener{
    public void actionPerformed(ActionEvent event){
        JButton src = (JButton) event.getSource();

        //create board
        String[][] board = {  {"1","2","3"},
                              {"4","5","6"},
                              {"7","8","9"}
                            };
        // who's turn?
        count++;
        if(count == 1 || count == 3 || count == 5 || count == 7 || count == 9 )
            letter = playerChoice;
        else if(count == 2 || count == 4 || count == 6 || count == 8 || count == 10)
            letter = computerChoice;


        //player choice - show button
        if(src.equals(one)){
            one.setText(letter);
            one.setEnabled(false);
            board[0][0]= letter;
        }else if(src.equals(two)){
            two.setText(letter);
            two.setEnabled(false);
            board[0][1] = letter; 
        }else if(src.equals(three)){
            three.setText(letter);
            three.setEnabled(false);
            board[0][2] = letter;
        }else if(src.equals(four)){
            four.setText(letter);
            four.setEnabled(false);
            board[1][0] = letter;
        }else if(src.equals(five)){
            five.setText(letter);
            five.setEnabled(false);
            board[1][1] = letter;
        }else if(src.equals(six)){
            six.setText(letter);
            six.setEnabled(false);
            board[1][2] = letter;
        }else if(src.equals(seven)){
            seven.setText(letter);
            seven.setEnabled(false);
            board[2][0] = letter;
        }else if(src.equals(eight)){
            eight.setText(letter);
            eight.setEnabled(false);
            board[2][1] = letter;
        }else if(src.equals(nine)){
            nine.setText(letter);
            nine.setEnabled(false);
            board[2][2] = letter;
        }


        System.out.println(Arrays.deepToString(board)); 

Answer 1

每次调用 actionPerformed 时，您都会创建一个新的局部变量 board...

private class Play implements ActionListener {

    public void actionPerformed(ActionEvent event) {
        JButton src = (JButton) event.getSource();

        //create board
        String[][] board = {{"1", "2", "3"},
                            {"4", "5", "6"},
                            {"7", "8", "9"}
                            };
        //...

这意味着状态在调用之间永远不会保存，而是在每次调用时重新创建。

相反，board 应该是一个实例字段，例如...

private class Play implements ActionListener {

    private String[][] board = {{"1", "2", "3"},
                                {"4", "5", "6"},
                                {"7", "8", "9"}
                                };

    public void actionPerformed(ActionEvent event) {
        JButton src = (JButton) event.getSource();

        count++;
        if(count == 1 || count == 3 || count == 5 || count == 7 || count == 9 )
            letter = playerChoice;
        else if(count == 2 || count == 4 || count == 6 || count == 8 || count == 10)
            letter = computerChoice;
        //...