java - 键监听器和键绑定(bind)并非每次编译都有效

Question

基本上我已经创建了一个连接到我的 JPanel 的关键监听器..有时当我编译并运行它时它确实工作得很好并且没有任何问题..但有时当我编译时它不会工作。它无法识别按键。

这是我在 JPanels 更新方法中用于关键监听器的代码:

if(keyListener.getMovingRight() == KeyEvent.VK_RIGHT){
            player.playerMoveRight();
        }
        if(keyListener.getMovingLeft() == KeyEvent.VK_LEFT){
            player.playerMoveLeft();
        }
        if(keyListener.getMovingUp() == KeyEvent.VK_UP){
            player.playerMoveUp();
        }
        if(keyListener.getMovingDown() == KeyEvent.VK_DOWN){
            player.playerMoveDown();
        }

上面的代码知道是否从此类按下了按键:

public class KeyBoard implements KeyListener {

    private int playerMoveUp;
    private int playerMoveDown;
    private int playerMoveLeft;
    private int playerMoveRight;

    public KeyBoard(){
        playerMoveUp = 0;
        playerMoveDown = 0;
        playerMoveLeft = 0;
        playerMoveRight = 0;
    }

    @Override
    public void keyTyped(KeyEvent keyEvent) {
    }

    @Override
    public void keyPressed(KeyEvent keyEvent) {

        //Switch statement to get which keys were pressed
        switch(keyEvent.getKeyCode()){

            case KeyEvent.VK_UP:
                playerMoveUp = keyEvent.getKeyCode();
                break;

            case KeyEvent.VK_DOWN:
                playerMoveDown = keyEvent.getKeyCode();
                break;

            case KeyEvent.VK_LEFT:
                playerMoveLeft = keyEvent.getKeyCode();
                break;

            case KeyEvent.VK_RIGHT:
                playerMoveRight = keyEvent.getKeyCode();
                break;
        }
    }

    @Override
    public void keyReleased(KeyEvent keyEvent) {

        //Switch statement to get which keys were released
        switch(keyEvent.getKeyCode()){

            case KeyEvent.VK_UP:
                playerMoveUp = 0;
                break;

            case KeyEvent.VK_DOWN:
                playerMoveDown = 0;
                break;

            case KeyEvent.VK_LEFT:
                playerMoveLeft = 0;
                break;

            case KeyEvent.VK_RIGHT:
                playerMoveRight = 0;
                break;
        }
    }

    public int getMovingUp(){
        return playerMoveUp;
    }
    public int getMovingDown(){
        return playerMoveDown;
    }
    public int getMovingLeft(){
        return playerMoveLeft;
    }
    public int getMovingRight(){
        return playerMoveRight;
    }
}

我当然通过这样做将关键监听器添加到 JPanel:

panel.addKeyListener(KeyBoardClasshere);

由于它不能正常工作，我尝试了其他称为“Key Bindigs”的东西，因为我听说这会增加我的机会..

我将其添加到 JPanel 类中，并在更新方法中注释掉了关键监听器:

   

public void keyBindingsInitialize(ActionMap am, InputMap im){
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), "Right");
        am.put("Right", RightBind);

        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "Left");
        am.put("Left", LeftBind);

        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "Up");
        am.put("Up", UpBind);

        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "Down");
        am.put("Down", DownBind);
    }
    
    Action RightBind = new AbstractAction(){
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            player.playerMoveRight();
        }
    };
    Action LeftBind = new AbstractAction(){
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            player.playerMoveLeft();
        }
    };
    Action UpBind = new AbstractAction(){
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            player.playerMoveUp();
        }
    };
    Action DownBind = new AbstractAction(){
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            player.playerMoveDown();
        }
    };

这也有效，但有时当我编译并运行项目时，它不起作用，然后如果我终止项目然后再次运行它，它就会起作用。在我看来，这太奇怪了。有人有建议吗？

编辑:我按照这个问题的答案:KeyListener on JPanel randomly unresponsive

我确实通过单击出现的按钮和空格键得到了响应，但没有得到更新方法中使用的键。现在，在我添加按钮后，有时当我运行应用程序时，我得到的只是一个灰色窗口，必须重新启动几次才能使其再次正常，就像我链接的问题一样。

Answer 1

尝试添加

setFocusable(true);

到 JPanel 的构造函数。