Java 为什么我按下“时会出现NullPointerException”；新游戏；？

我正在制作数独游戏的控制器。当您运行我的SudokuMain.java文件，并单击页面顶部的“文件”，然后选择“新建游戏”时，我得到异常：

线程“AWT-EventQueue-0”java.lang.NullPointerException中出现异常

我有一个用于“新游戏”的ActionListener来创建一个名为“CreateBoard”的JDialog对象，并提示用户输入“每个区域的行数”和“每个区域的列数”，然后按“CreateBoard”，或者按“Cancel”将其删除

我不确定我做错了什么，但我觉得问题在于内部类菜单。感谢您的帮助

// Allow short name access to following classes
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

public class SudokuMain extends JComponent {

  public static void main(String[] args) {
    new SudokuMain();
  }

  private SudokuBase board;
  private SudokuView view;

  private JFrame win;
  private JPanel center;
  private JPanel west;
  private JPanel east;
  private JPanel cells;

  private final Dialog1 setWin1;

  public SudokuMain() {

   // start game
   view = new SudokuView(makeBoard());
   board = makeBoard();

   win = new JFrame("Sudoku");
   center = new JPanel();
   west = new JPanel();
   east = new JPanel();

   // "player" cells for current Sudoku board
   cells = new SetSymbols(view);
   // the 1st set-up window
   setWin1 = new Dialog1(this, "New Game", true);

   // create menu bar
   MenuAtTop menuBar = new MenuAtTop(this);
   win.setJMenuBar(menuBar);

   win.setLayout(new BorderLayout());
   view.setSelected(1, 1);
   west.setLayout(new BorderLayout());
   east.setLayout(new BorderLayout());
   center.setLayout(new FlowLayout());

   west.add(cells);
   east.add(view, BorderLayout.CENTER);
   center.add(west);
    center.add(east);

   win.add(center);

   win.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
   win.pack();
   win.setVisible(true);

 }

class SudokuControlButton extends JPanel {

  private int row;
  private int col;

  // row of selected cell
  private int selRow;
  // column of selected cell
  private int selCol;

  // the value that corresponds with the desired symbol
  private int value;

  /**
   * Constructs SudokuControlButton object; the graphic "button"
   * to control the board.
   */
  public SudokuControlButton(final SudokuView view) {

    setPreferredSize(new Dimension(40, 40));
    setBackground(Color.LIGHT_GRAY);

    //value = 0;

    addMouseListener(new MouseListener() {

      public void mouseClicked(MouseEvent e) {
        selRow = view.getSelectedRow();
        selCol = view.getSelectedColumn();

        if(!board.isGiven(selRow, selCol)) {
          board.setValue(selRow, selCol, value);

        view.repaint();
        } else {  // have system beep sound
          getToolkit().beep();
        }

        repaint();
      }

      public void mouseEntered(MouseEvent e){
        // set to "highlighted" color
        setBackground(Color.WHITE);

        repaint();
      }

      public void mouseExited(MouseEvent e){
        // set to default color
        setBackground(Color.LIGHT_GRAY);

        repaint();
      }

      public void mousePressed(MouseEvent e){
        // set to "active" color
        setBackground(Color.YELLOW);

        repaint();
      }

      public void mouseReleased(MouseEvent e){
      }

    });
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);

    switch(value) {
      case 0:
      drawSymbol(g, 0);
      break;
    case 1:
      drawSymbol(g, 1);
      break;
    case 2:
      drawSymbol(g, 2);
      break;
    case 3:
      drawSymbol(g, 3);
      break;
    case 4:
      drawSymbol(g, 4);
      break;
    case 5:
      drawSymbol(g, 5);
      break;
    case 6:
      drawSymbol(g, 6);
      break;
    case 7:
      drawSymbol(g, 7);
      break;
    case 8:
      drawSymbol(g, 8);
      break;
    case 9:
      drawSymbol(g, 9);
      break;
    case 10:
      drawSymbol(g, 10);
      break;
    case 11:
      drawSymbol(g, 11);
      break;
    case 12:
      drawSymbol(g, 12);
      break;
  }

}

/**
 * This method draws the symbol that corresponds with 
 * the specified value (0-12).
 * 
 * @param g The drawing mechanism.
 * @param value The specified value.
 */
public void drawSymbol(Graphics g, int value) {

  if(value < 0 || value > 12) {
    String msg = "Value cannot be less than 1 or greater than 12.";
    throw new IllegalArgumentException(msg);
  }

  // enable drawing with "thick" lines
  Graphics2D g2 = (Graphics2D) g;
  g2.setStroke(new BasicStroke(3));

  switch(value) {
    case 0:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      break;
    case 1:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      break;
    case 2:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      g2.drawLine(10, 5, 10, 45);
      break;
    case 3:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      g2.drawLine(10, 5, 10, 45);
      g2.drawLine(15, 5, 15, 45);
      break;
    case 4:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      g2.drawLine(10, 5, 10, 45);
      g2.drawLine(15, 5, 15, 45);
      g2.drawLine(20, 5, 20, 45);
      break;
    case 5:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      g2.drawLine(10, 5, 10, 45);
      g2.drawLine(15, 5, 15, 45);
      g2.drawLine(20, 5, 20, 45);
      g2.drawLine(25, 5, 25, 45);
      break;
    case 6:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 45);
      g2.drawLine(10, 5, 10, 45);
      g2.drawLine(15, 5, 15, 45);
      g2.drawLine(20, 5, 20, 45);
      g2.drawLine(25, 5, 25, 45);
      g2.drawLine(30, 5, 30, 45);
      break;
    case 7:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 20);
      g2.drawLine(10, 5, 10, 20);
      g2.drawLine(15, 5, 15, 20);
      g2.drawLine(20, 5, 20, 20);
      g2.drawLine(25, 5, 25, 20);
      g2.drawLine(30, 5, 30, 20);
      g2.drawLine(5, 30, 5, 45);
      break;
    case 8:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 20);
      g2.drawLine(10, 5, 10, 20);
      g2.drawLine(15, 5, 15, 20);
      g2.drawLine(20, 5, 20, 20);
      g2.drawLine(25, 5, 25, 20);
      g2.drawLine(30, 5, 30, 20);
      g2.drawLine(5, 30, 5, 45);
      g2.drawLine(10, 30, 10, 45);
      break;
    case 9:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g2.drawLine(5, 5, 5, 20);
      g2.drawLine(10, 5, 10, 20);
      g2.drawLine(15, 5, 15, 20);
      g2.drawLine(20, 5, 20, 20);
      g2.drawLine(25, 5, 25, 20);
      g2.drawLine(30, 5, 30, 20);
      g2.drawLine(5, 30, 5, 45);
      g2.drawLine(10, 30, 10, 45);
      g2.drawLine(15, 30, 15, 45);
      break;
    case 10:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g.drawLine(5, 5, 5, 20);
      g.drawLine(10, 5, 10, 20);
      g.drawLine(15, 5, 15, 20);
      g.drawLine(20, 5, 20, 20);
      g.drawLine(25, 5, 25, 20);
      g.drawLine(30, 5, 30, 20);
      g.drawLine(5, 30, 5, 45);
      g.drawLine(10, 30, 10, 45);
      g.drawLine(15, 30, 15, 45);
      g.drawLine(20, 30, 20, 45);
      break;
    case 11:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g.drawLine(5, 5, 5, 20);
      g.drawLine(10, 5, 10, 20);
      g.drawLine(15, 5, 15, 20);
      g.drawLine(20, 5, 20, 20);
      g.drawLine(25, 5, 25, 20);
      g.drawLine(30, 5, 30, 20);
      g.drawLine(5, 30, 5, 45);
      g.drawLine(10, 30, 10, 45);
      g.drawLine(15, 30, 15, 45);
      g.drawLine(20, 30, 20, 45);
      g.drawLine(25, 30, 25, 45);
      break;
    case 12:
      // draw borders
      g.drawRect(0, 0, 50, 50);
      // draw symbol
      g.drawLine(5, 5, 5, 20);
      g.drawLine(10, 5, 10, 20);
      g.drawLine(15, 5, 15, 20);
      g.drawLine(20, 5, 20, 20);
      g.drawLine(25, 5, 25, 20);
      g.drawLine(30, 5, 30, 20);
      g.drawLine(5, 30, 5, 45);
      g.drawLine(10, 30, 10, 45);
      g.drawLine(15, 30, 15, 45);
      g.drawLine(20, 30, 20, 45);
      g.drawLine(25, 30, 25, 45);
      g.drawLine(30, 30, 30, 45);
      break;
    }

  }

 }

class MenuAtTop extends JMenuBar implements ActionListener{

  private SudokuMain main;

  private JMenu fileMenu;
  private JMenuItem newGame;

  private JDialog createNewWin; 

  public MenuAtTop(final SudokuMain m) {

    fileMenu = new JMenu("File");
    add(fileMenu);

    newGame = new JMenuItem("New Game");
    newGame.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N,
                                                  ActionEvent.CTRL_MASK));
    fileMenu.add(newGame);
    newGame.addActionListener(this);

  }

  public void actionPerformed(ActionEvent e) {
    setEnabled(false);
    createNewWin = new Dialog1(main, "Create New Board", true);
  }

}

class Dialog1 extends JDialog {

  private JTextField rows;
  private JTextField cols;
  private JButton createBoard; 
  private JButton cancel;
  private JLabel rowLabel;
  private JLabel colLabel;
  private JLabel errorMes;


  private JPanel center;
  private JPanel north;
  private JDialog setUpWin2;

  /**
   * Constructs Dialog1 object.
   * 
   * @param win The window containing the dialog box.
   * @param header The title of dialog box.
   * @param modal Whether dialog box is modal or not.
   */
  public Dialog1(final SudokuMain win, String header, boolean modal) {
    // call superclass constructor
    super();

    // instantiate and bind to references
    rows = new JTextField(2);
    cols = new JTextField(2);
    createBoard = new JButton("Create Board");
    cancel = new JButton("Cancel");
    rowLabel = new JLabel("Rows per region: ");
    colLabel = new JLabel("Columns per region: ");
    errorMes = new JLabel();

    north = new JPanel(new FlowLayout());
    center = new JPanel(new FlowLayout());

    // set characteristics
    setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
    setTitle(header);
    setModal(modal);
    setLayout(new BorderLayout());

    // set characteristics of error message
    errorMes.setForeground(Color.RED);
    errorMes.setFont(new Font("Arial", Font.ITALIC, 12));
    errorMes.setVisible(false);

    cancel.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        setVisible(false);
      }
    });

    createBoard.addActionListener(new ActionListener() {

      public void actionPerformed(ActionEvent e) {
        int newRows;
        int newCols;
        int newSize;

        try{
          newRows = Integer.parseInt(rows.getText());
          newCols = Integer.parseInt(cols.getText());
        } catch (NumberFormatException exc) {
          newRows = 0;
          newCols = 0;
        }

        newSize = newRows * newCols;
        // input validation
        if(newSize <= 0 && newSize > 12) {
          errorMes.setText("Rows times columns cannot be greater than 12!");
          errorMes.setVisible(true);
          pack();

        } else{ // valid input
          errorMes.setVisible(false);
          setVisible(false);
          setUpWin2 = new Dialog2(win, "New Sudoku", newRows, newCols, true);
        }
      }});


    // place error message in the center
    center.add(errorMes);

    // place labels for rows and columns at the top 
    north.add(rowLabel);
    north.add(rows);
    north.add(colLabel);
    north.add(cols);

    add(center, BorderLayout.CENTER);
    add(north, BorderLayout.NORTH);

    pack();

    if(!win.win.isVisible()) {
      dispose();
    }

  }
}

class Dialog2 extends JDialog {

  private SudokuView view;

  private JPanel panel;
  private JPanel northPanel;
  private JPanel cells;

  private JButton setGivens; 
  private JButton cancel;

  /**
   * Constructs Dialog2 object.
   * 
   * @param win The window containing the dialog box.
   * @param header The title of the dialog box.
   * @param rows the rows to the new SudokuBoard to be constructed in the dialog box
   * @param cols the columns to the new SudokuBoard to be constructed in the dialog box
   * @param modal boolean value for whether the box is modal or not
   */
  public Dialog2(final SudokuMain mainWin, String header, int rows, int cols,
                 boolean modal) {
    // call superclass constructor
    super();

    // instantiate and bind to references
    view = new SudokuView(new SudokuBoard(rows, cols));
    panel = new JPanel();
    northPanel = new JPanel();
    setGivens = new JButton("Set Givens");
    cancel = new JButton("Cancel");
    cells = new SetSymbols(view);

    // set up characteristics 
    setTitle(header);
    setModal(modal);
    setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    setLayout(new FlowLayout());
    panel.setLayout(new BorderLayout());
    northPanel.setLayout(new FlowLayout());


    setGivens.addActionListener(new ActionListener() {

      public void actionPerformed(ActionEvent e) {
        // set "given" cells
        makeBoard().fixGivens();

        // have window refer to new board
        west.remove(mainWin.view);
        mainWin.east.remove(mainWin.cells);

        mainWin.view = view;
        mainWin.cells = cells;

        mainWin.west.add(mainWin.view);
        mainWin.east.add(mainWin.cells);

        setVisible(false);

      }});

    cancel.addActionListener(new ActionListener() {
     public void actionPerformed(ActionEvent e) {
        setVisible(false);
    }});

    // place buttons at the top
    northPanel.add(setGivens);
    northPanel.add(cancel);

    panel.add(view, BorderLayout.CENTER);
    panel.add(northPanel, BorderLayout.NORTH);

    add(panel);
    add(cells);

    setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    pack();
    setVisible(true);

  }

}

class SetSymbols extends JPanel {

// temporary board to help create graphic "buttons"
private SudokuBoard tempBd;

/**
 * Constructs SetSymbols object.
 * @param view The SudokuView object for SetSymbols.
 */
public SetSymbols(final SudokuView view) {
  // instantiate and bind to reference
  tempBd = new SudokuBoard(1, board.getBoardSize() + 1);

  setLayout(new GridLayout((tempBd.getBoardSize())/2 + 1, 2));

  for(int colCell = 0; colCell < tempBd.getBoardSize(); colCell++) {

    // cannot be changed after set/instantiated
    final int value = colCell;
    final JPanel cell = new JPanel();
    final Color defaultColor = cell.getBackground();

    // set characteristics
    cell.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    // set value for each graphic "button"
    tempBd.setValue(0, colCell, colCell);
    // add the appropriate symbol to each graphic "button"
    cell.add(view.new SudokuCell(0, colCell, tempBd));

    cell.addMouseListener(new MouseListener() {
      // whether inside graphic "button" or not
      boolean insideCell;

      public void mouseClicked(MouseEvent e) {
        int selRow = view.getSelectedRow();
        int selCol = view.getSelectedColumn();

        if(!board.isGiven(selRow, selCol)) {
          board.setValue(selRow, selCol, value);

          view.repaint();
        }
        else {  // have system beep sound
          cell.getToolkit().beep();
        }

      }

      public void mouseEntered(MouseEvent e) {
        insideCell = true;
        // set to "highlighted" color
        cell.setBackground(Color.WHITE);

        view.repaint();
      }

      public void mouseExited(MouseEvent e) {
        insideCell = false;
        // set to default color
        cell.setBackground(defaultColor);

        view.repaint();
      }

      public void mousePressed(MouseEvent e) {
        // set to "active" color
        cell.setBackground(Color.YELLOW);

        view.repaint();
      }

      public void mouseReleased(MouseEvent e) {
        if(insideCell) {
          cell.setBackground(Color.YELLOW);
        }
        else {  // outside of symbol's cell
          cell.setBackground(defaultColor);
        }

        view.repaint();
      }
    });

    // add graphic "button"
    add(cell);

  }

  // handle possible "empty" graphic "button"
  if(tempBd.getBoardSize() % 2 != 0) {
    JPanel empty = new JPanel();
    empty.setBackground(Color.LIGHT_GRAY);
    empty.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    add(empty);
   }

   }

  }

  public static SudokuBase makeBoard() {
    SudokuBase board = new SudokuBoard(2, 3);
    board.setValue(0, 3, 6);
    board.setValue(0, 5, 1);
    board.setValue(1, 2, 4);
    board.setValue(1, 4, 5);
    board.setValue(1, 5, 3);
    board.setValue(2, 3, 3);
    board.setValue(3, 2, 6);
    board.setValue(4, 0, 2);
    board.setValue(4, 1, 3);
    board.setValue(4, 3, 1);
    board.setValue(5, 0, 6);
    board.setValue(5, 2, 1);
    board.fixGivens();
    return board;
  }

}

//允许短名称访问以下类
导入java.awt.*；
导入java.awt.event.*；
导入javax.swing.*；
导入java.util.*；
公共类SudokuMain扩展了JComponent{
公共静态void main（字符串[]args）{
新SudokuMain（）；
}
私人SudokuBase板；
私人SudokuView视图；
私营部门赢得；
私人杰帕内尔中心；
私人杰帕内尔西；
私人杰帕内尔东区；
私人JPanel细胞；
私有最终对话框1 setWin1；
公共SudokuMain（）{
//开始比赛
视图=新的SudokuView（makeBoard（））；
board=makeBoard（）；
win=新的JFrame（“数独”）；
中心=新的JPanel（）；
west=新JPanel（）；
east=新JPanel（）；
//当前数独板的“玩家”单元
单元格=新的设置符号（视图）；
//第一个设置窗口
setWin1=newdialog1（这是“新游戏”，true）；
//创建菜单栏
MenuAtTop menuBar=新的MenuAtTop（此菜单）；
win.setJMenuBar（菜单栏）；
win.setLayout（新的BorderLayout（））；
视图（1，1）；
setLayout（新的BorderLayout（））；
setLayout（新的BorderLayout（））；
setLayout（新的FlowLayout（））；
添加（单元格）；
添加（视图、边框布局、中心）；
中加（西）；
中加（东）；
win.add（中心）；
win.setDefaultCloseOperation（JFrame.DISPOSE\u ON\u CLOSE）；
win.pack（）；
win.setVisible（true）；
}
类SudokuControlButton扩展了JPanel{
私人int row；
私人国际学院；
//选定单元格的行
私家车；
//选定单元格的列
私家车；
//与所需符号对应的值
私有int值；
/**
*构造SudokuControlButton对象；图形“按钮”
*控制董事会。
*/
公共数独控制按钮（最终数独视图）{
setPreferredSize（新尺寸（40,40））；
立根背景（颜色：浅灰色）；
//数值=0；
addMouseListener（新MouseListener（）{
公共无效mouseClicked（MouseEvent e）{
selRow=view.getSelectedRow（）；
selCol=view.getSelectedColumn（）；
如果（！board.isGiven（selRow，selCol））{
线路板设置值（selRow、selCol、value）；
view.repaint（）；
}否则{//系统会发出嘟嘟声
getToolkit（）.beep（）；
}
重新油漆（）；
}
公共无效鼠标事件（鼠标事件e）{
//设置为“突出显示”颜色
挫折地面（颜色：白色）；
重新油漆（）；
}
公共无效mouseExited（MouseEvent e）{
//设置为默认颜色
立根背景（颜色：浅灰色）；
重新油漆（）；
}
公共无效鼠标按下（MouseEvent e）{
//设置为“活动”颜色
挫折地面（颜色：黄色）；
重新油漆（）；
}
公共无效MouseEvent（MouseEvent e）{
}
});
}
公共组件（图形g）{
超级组件（g）；
开关（值）{
案例0：
绘图符号（g，0）；
打破
案例1：
绘图符号（g，1）；
打破
案例2：
绘图符号（g，2）；
打破
案例3：
绘图符号（g，3）；
打破
案例4：
绘图符号（g，4）；
打破
案例5：
绘图符号（g，5）；
打破
案例6：
绘图符号（g，6）；
打破
案例7：
绘图符号（g，7）；
打破
案例8：
绘图符号（g，8）；
打破
案例9：
绘图符号（g，9）；
打破
案例10：
绘图符号（g，10）；
打破
案例11：
绘图符号（g，11）；
打破
案例12：
绘图符号（g，12）；
打破
}
}
/**
*此方法绘制与对应的符号
*指定的值（0-12）。
* 
*@param g是绘图机制。
*@param value指定的值。
*/
公共空白绘图符号（图形g，int值）{
如果（值<0 | |值>12）{
String msg=“值不能小于1或大于12。”；
抛出新的IllegalArgumentException（msg）；
}
//启用“粗”线绘图
图形2d g2=（图形2d）g；
g2.设定行程（新基本行程（3））；
开关（值）{
案例0：
//划界
g、 drawRect（0,0,50,50）；
打破
案例1：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
打破
案例2：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
g2.抽绳（10,5,10,45）；
打破
案例3：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
g2.抽绳（10,5,10,45）；
g2.抽绳（15,5,15,45）；
打破
案例4：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
g2.抽绳（10,5,10,45）；
g2.抽绳（15,5,15,45）；
g2.抽绳（20,5,20,45）；
打破
案例5：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
g2.抽绳（10,5,10,45）；
g2.抽绳（15,5,15,45）；
g2.抽绳（20,5,20,45）；
g2.抽绳（25,5,25,45）；
打破
案例6：
//划界
g、 drawRect（0,0,50,50）；
//绘图符号
g2.抽绳（5,5,5,45）；
g2.抽绳（10,5,10,45）；
g2.抽绳（15,5,15,45）；
g2.抽绳（20,5,20,45）；
G