在Java按鍵上啟動計時器

Question

我想在單擊“ d”按鈕時啟動一個計時器。 這是為了使播放器動畫。 按下鍵后計時器沒有啟動，該怎么辦？

我的代碼是這樣的：

public class Game extends JPanel implements KeyListener {
//Player variables
private BufferedImage playerStanding;
private BufferedImage playerWalking;
private BufferedImage playerFrame;
private boolean walking = false;
private final int PLAYER_HEIGHT = 100;
private final int PLAYER_WIDTH = 100;
private final int INITIAL_X = 0;
private final int INITIAL_Y = 500;
private int x = INITIAL_X;
private int y = INITIAL_Y;
//The timer I want to start on keypress-> "d"
private Timer playerAnimationTimer;



public Game() {
    setPreferredSize(new Dimension(800, 800));
    setBackground(Color.CYAN);
    //Player
    try {
        playerStanding = ImageIO.read(getClass().getResource("player1.gif"));
        playerWalking = ImageIO.read(getClass().getResource("player2.gif"));
        playerFrame = playerStanding;


    }
    catch (IOException ex) {
        ex.printStackTrace();
    }

    playerAnimationTimer = new Timer(500, new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            walking = !walking;
            playerFrame = walking ? playerWalking : playerStanding;
            x += 10;
            if (x > getWidth() - PLAYER_WIDTH) {
                x = INITIAL_X;
            }
            repaint();
        }
    });
    playerAnimationTimer.setRepeats(true);
}

public Dimension setPreferredSize() {
    return new Dimension(800, 800);
}



@Override
public void paintComponent(Graphics graphics) {
    super.paintComponent(graphics);

    Graphics2D graphics2D = (Graphics2D) graphics;
    if (playerFrame != null) {
        graphics2D.drawImage(playerFrame, x, y, PLAYER_WIDTH, PLAYER_HEIGHT, this);
    }


    graphics2D.dispose();
}

@Override
public void keyTyped(KeyEvent e) {
    //This doesn't work
    playerAnimationTimer.start();
}

@Override
public void keyPressed(KeyEvent e) {

}

@Override
public void keyReleased(KeyEvent e) {

}
}
//The class to hold the gamepanel
public class StartGame extends JFrame implements ActionListener {
private static JButton startGame = new JButton();

StartGame() {
    setDefaultCloseOperation(WindowConstants.HIDE_ON_CLOSE);
    setSize(200, 100);
    setVisible(true);
    setBackground(Color.BLUE);
    setLocationRelativeTo(null);

    startGame.setText("Play!");
    startGame.setSize(100, 25);
    startGame.addActionListener(this);
    add(startGame);
}

@Override
public void actionPerformed(ActionEvent e) {
    if (e.getSource() == startGame) {
        this.setVisible(false);
        new GameWindow();
    }
}
public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            new StartGame();
        }
    });
}
}

當我單擊“ d”按鈕時，如何使計時器啟動？

Answer 1

您的KeyListener無法正常工作，因為您絕不會將KeyListener添加到具有焦點的組件中，這是KeyListener正常工作所必需的。

我建議您改用“鍵綁定”作為更安全的方法來捕獲所需的按鍵。

順便說一句，切勿處置JVM提供給您的Graphics對象。

為了獲得更好的答案，請編輯您的代碼以使其符合mcve標准。 您不應該使用任何圖像文件，並且應不更改地為我們編譯和運行。

Answer 2

您可以像這樣設置私有計時器並像這樣啟動它...

public void startTimer(){
   timer.start();
   timer.setRepeats(true);
}