连接 GUI 和游戏

Question

我正在尝试在 java 中使用游戏 class 构建 GUI。我一直收到 NullPointerException 并且我不知道为什么，我以为我正在将对象 "cPlayer" 传递给小程序，然后小程序将它传递给 JPanel 部分（它应该与 cPlayer 比较命中或未命中）但是我不知道我做错了什么。有没有其他方法可以将 cPlayer 对象传递给小程序，然后传递给 JPanel？

public class gamePlay {
    public final static ComputerBoard cPlayer = new ComputerBoard();

    public static void main(String args){
        BattleshipApplet play = new BattleshipApplet();
        play.setBoard(cPlayer);

    }
}

public class BattleshipApplet extends JApplet {
    private final JButton playButton = new JButton("Play");
    private final JLabel msgBar = new JLabel("Click Play to start game");
    private BoardPanel panel;
    private ComputerBoard game;


    public BattleshipApplet(){
        playButton.addActionListener(this::playButtonClicked);  
    }

    public void init(){
        configureGui();
    }

    private void configureGui(){
        setLayout(new BorderLayout());
        JPanel buttons = new JPanel(new FlowLayout(FlowLayout.LEFT));
        buttons.setBorder(BorderFactory.createEmptyBorder(0,5,0,0));
        buttons.add(playButton);
        add(buttons, BorderLayout.NORTH);
        msgBar.setBorder(BorderFactory.createEmptyBorder(10,10,5,5));
        add(createBoardPanel(), BorderLayout.CENTER);
        add(msgBar, BorderLayout.SOUTH);
    }

    private BoardPanel createBoardPanel(){
        panel = new BoardPanel(game);
        return panel;
    }

    private void displayMessage(String msg){
        msgBar.setText(msg);
    }

    private void playButtonClicked(ActionEvent event){
        displayMessage("Game has started!");

    }

    void setBoard(ComputerBoard b){
        game = b;
    }

}

public class BoardPanel extends JPanel  {
    private static final int ROWS = 10;
    private static final int CELL_WIDTH = 28;
    private static final int PAD = 20;
    private static final Color GRID_COLOR = Color.blue;
    private static final Color CIRCLE_COLOR_HIT = Color.red;
    private static final Color CIRCLE_COLOR_MISS = Color.white;
    private static final Color TEXT_COLOR = Color.blue;
    private static final int SML_GAP = 2;
    private boolean[][] grid = new boolean[ROWS][ROWS];
    private int counter;
    private int x, y;
    private boolean gameBoardpiece;
    ComputerBoard gameBoard;


    public BoardPanel(ComputerBoard b) {
        addMouseListener((MouseListener) new MyMouse());
        counter =0;
        gameBoard = b;
        gameBoardpiece = false;
    }



    public void reset() {
        grid = new boolean[ROWS][ROWS]; // fills grid with false
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);


        // draws grid
        g.setColor(GRID_COLOR);
        for (int i = 0; i <= ROWS; i++) {
            int x1 = PAD + i * CELL_WIDTH;
            int y1 = PAD;
            int x2 = x1;
            int y2 = PAD + CELL_WIDTH * ROWS;
            g.drawLine(x1, y1, x2, y2);
            g.drawLine(y1, x1, y2, x2);

        }

        // iterate through the grid boolean array
        // draw circles if the grid value is true.
        int w = CELL_WIDTH - 2 * SML_GAP; // width of the circle to draw
        int h = w;
        // nested for loop to go through the grid array
        for (int r = 0; r < grid.length; r++) {
            for (int c = 0; c < grid[r].length; c++) {
                if (grid[r][c]) {
                    //if was a hit
                    if(gameBoardpiece == false){
                        g.setColor(CIRCLE_COLOR_HIT);
                    }
                    //shot was a miss
                    else{
                        g.setColor(CIRCLE_COLOR_MISS);
                    }
                    int x = PAD + c * CELL_WIDTH + SML_GAP;
                    int y = PAD + r * CELL_WIDTH + SML_GAP;
                    g.fillOval(x, y, w, h);
                }
            }
        }
        //states the number of shots in the game
        g.setColor(TEXT_COLOR);
        g.drawString("Shots: "+counter, 305,300 );
    }



    private class MyMouse extends MouseAdapter {
        public void mousePressed(MouseEvent e) {
            x = e.getX();
            y = e.getY();

            if (x < PAD || y < PAD  ) {
                // clicked above or to right of grid
                return;
            }

            int r = (y - PAD) / CELL_WIDTH;
            int c = (x - PAD) / CELL_WIDTH;

            // if clicked to right or below grid.
            if (r >= ROWS || c >= ROWS) {
                return;
            }

            if(gameBoard.matchBoard(r,c) == 0){
                gameBoardpiece = true;
            }
            if(gameBoard.matchBoard(r,c) == 1){
                gameBoardpiece = false;
            }
            counter++;
            grid[r][c] = true;
            repaint();
        }
    }
}

我收到的错误信息是：

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
    at battleship.BoardPanel$MyMouse.mousePressed(BoardPanel.java:113)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access0(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

小程序的生命周期不同于应用程序的生命周期。如果此小程序在小程序通常运行所在的环境中运行，则不会调用 main() 方法。上下文调用小程序的构造函数后，生命周期将从调用小程序的 init() 方法开始。

因此像下面这样的东西会更好。

public void init(){
    ComputerBoard cPlayer = new ComputerBoard();
    setBoard(cPlayer);
    configureGui();
}

或者完全取消 setBoard 方法并编写

public void init(){
    game = new ComputerBoard();
    configureGui();
}

连接 GUI 和游戏

Connecting GUI with game

java

swing

applet