我正在使用Swing在Java中创建一个老式的Snake游戏。我已经读过为了实时捕获输入，我需要在一个新线程中运行我的游戏循环，这样它的wait()方法不会干扰输入捕获。我已经InputCapture课程实施了KeyListener，我实施了keyPressed()这样的方法：
public class InputCapture implements KeyListener {
private Direction capturedDirection;
//Methods
@Override
public void keyPressed(KeyEvent e) {
boolean inputConsoleDebug = true;
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
capturedDirection = Direction.left;
if (inputConsoleDebug) System.out.println("LEFT");
} else if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
capturedDirection = Direction.right;
if (inputConsoleDebug) System.out.println("RIGHT");
} else if (e.getKeyCode() == KeyEvent.VK_UP) {
capturedDirection = Direction.up;
if (inputConsoleDebug) System.out.println("UP");
} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
capturedDirection = Direction.down;
if (inputConsoleDebug) System.out.println("DOWN");
}
}
@Override
public void keyReleased(KeyEvent e) {
}
@Override
public void keyTyped(KeyEvent e) {
}
public Direction getCapturedDirection() {
return capturedDirection;
}
}
然后我将Game类扩展为Thread并将游戏循环代码放入run()方法中：
public class Game extends Thread {
private Board board;
private Snake snake;
private JFrame frame;
private long waitTime;
private int difficultyStep;
private Direction inputDirection;
private InputCapture inputManager;
//Constructors
Game(Dimension boardSize) {
//Set difficulty
int applesToWin = boardSize.width * boardSize.height - 1;
final int easiestWaitTime = 1000;
final int hardestWaitTime = 100;
difficultyStep = (easiestWaitTime - hardestWaitTime) / applesToWin;
waitTime = easiestWaitTime;
//Set starting point
final int startingPointX = boardSize.width / 2;
final int startingPointy = boardSize.height / 2;
//Set board and snake
board = new Board(boardSize);
snake = new Snake(board, startingPointX, startingPointy);
//Set window Frame
frame = new JFrame(SnakeApplication.getApplicationName());
frame.setContentPane(board);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.pack();
frame.setResizable(false);
frame.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
super.windowClosing(e);
interrupt();
}
});
//Set input manager
inputManager = new InputCapture();
frame.addKeyListener(inputManager);
inputDirection = null;
}
//Methods
public void run() {
board.spawnApple();
while (!isWon()) {
try {
sleep(waitTime);
} catch (InterruptedException e) {
return;
}
try {
inputDirection = inputManager.getCapturedDirection();
snake.move(inputDirection);
} catch (LosingMove e) {
showGameOverDialog();
return;
}
board.repaint();
}
showWinDialog();
}
JFrame getFrame() {
return frame;
}
private boolean isWon() {
for (int row = 0; row < board.getFields().length; row++) {
for (int col = 0; col < board.getFields()[0].length; col++) {
if (!(board.getFields()[row][col].getContent() instanceof Snake.SnakeNode)) return false;
}
}
return true;
}
private void showGameOverDialog() {
JFrame gameOverFrame = new JFrame();
JOptionPane.showMessageDialog(gameOverFrame, "Game Over!");
}
private void showWinDialog() {
JFrame gameOverFrame = new JFrame();
JOptionPane.showMessageDialog(gameOverFrame, "You Win!");
}
}
在我的MainMenu课程中，我点击了“新游戏”按钮时调用了startNewGame()方法。此方法创建Game对象并通过调用start()方法启动新线程。
public class MainMenu {
//Form components references
private JButton exitButton;
private JFrame frame;
private JPanel mainPanel;
private JButton newGameButton;
private JLabel titleLabel;
//Constructors
MainMenu() {
//Set window Frame
frame = new JFrame(SnakeApplication.getApplicationName());
frame.setContentPane(mainPanel);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setResizable(false);
frame.pack();
newGameButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
startNewGame();
}
});
exitButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
exitGame();
}
});
}
JFrame getFrame() {
return frame;
}
private Dimension showBoardSizeDialog() {
Frame boardSizeFrame = new Frame();
int width = Integer.parseInt(JOptionPane.showInputDialog(boardSizeFrame, "Set board's width:"));
int height = Integer.parseInt(JOptionPane.showInputDialog(boardSizeFrame, "Set board's height:"));
return new Dimension(width, height);
}
private void startNewGame() {
Dimension boardSize = showBoardSizeDialog();
frame.setVisible(false);
Game game = new Game(boardSize);
game.getFrame().setVisible(true);
//Starting game loop in a new thread
game.start();
try {
game.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
frame.setVisible(true);
}
}
但是在测试应用程序时，它会陷入游戏循环并且根本不捕获输入。为什么？我试图调试它，但每次启动新线程时它都会陷入游戏循环。仅当主线程结束执行时才会绘制Board本身。为什么？如果执行被卡在那里，它不应该在游戏循环中多次重新绘制吗？
另外，当单击帧的关闭按钮时，我已经进行了线程中断（红色X按钮），因此执行可以返回MainMenu并重新出现，但单击红色关闭按钮无效。
答案 0 :(得分：2)
由于game.join()中对startNewGame的调用，程序冻结了。 join使来自的线程继续执行，直到 on 上的线程终止。在你的情况下，join会破坏使用另一个线程的目的，所以你应该删除它。
但是还有其他问题。你可能不应该使用一个线程。 You should probably use a Swing Timer。 Swing isn't thread-safe，我已经可以看到一些代码不是线程安全的地方。 （例如，您需要将capturedDirection声明为volatile。）使用Swing编写正确的多线程代码有点复杂，只使用计时器会更简单。
否则，如果您不使用计时器，则需要使用例如游戏线程（写入共享游戏状态）和绘制的Swing线程（可能是从共享游戏状态读取）之间的同步。如果不这样做，您可能会遇到难以诊断的问题。
答案 1 :(得分：0)
您应该使Game课程延长Runnable而不是Thread。
然后让游戏进入另一个角色：
Game theGame = ... // initialization code here
new Thread(theGame).start();