Java：使用KeyAdapter的帮助

Question

public class Board extends JPanel implements ActionListener{

Timer timer;
Tank tank = new Tank();

boolean boardset;

public Board(){
setBackground(Color.BLACK);

ImageIcon alien1ii = new ImageIcon(this.getClass().getResource("si_Alien1.png"));
Image alien1 = alien1ii.getImage();
ImageIcon alien2ii = new ImageIcon(this.getClass().getResource("si_Alien2.png"));
Image alien2 = alien2ii.getImage();
ImageIcon alien3ii = new ImageIcon(this.getClass().getResource("si_Alien3.png"));
Image alien3 = alien3ii.getImage();

timer = new Timer(5, this);
timer.start();

addKeyListener(new TAdapter());

JButton button = new JButton(new AbstractAction("hello2"){
    @Override
    public void actionPerformed(ActionEvent e){
        boardset = false;
    }
}); 
this.add(button);

//actual game
setFocusable(true);
setDoubleBuffered(true);
}

public void paint(Graphics g){
    super.paint(g);
    g.setColor(Color.WHITE);

    Graphics2D g2d = (Graphics2D) g;
    g2d.drawImage(tank.getTank(), tank.getx(), tank.getY(), this);

    g2d.drawLine(0, (tank.getY()+25), 400, (tank.getY()+25));

    Toolkit.getDefaultToolkit().sync();     
    g.dispose();
}

public class TAdapter extends KeyAdapter{
    public void keyPressed(KeyEvent e){
        tank.keyPressed(e);
        System.out.println("pressedddddddddddddddddd");
    }
    public void keyReleased(KeyEvent e){
        tank.keyReleased(e);
    }
}

public void setBoardset(boolean x){
    boardset = x;
}

public boolean getBoardset(){
    return boardset;
}

@Override
public void actionPerformed(ActionEvent e) {
        repaint();
        tank.move();
    }

}

在我看来，这应该是非常简单的，现在我使用这个print语句来查看类是否真的识别按键：public class TAdapter extends KeyAdapter{public void keyPressed（KeyEvent e）{tank.keyPressed(e)；system.out.println（“presseddddddddddddddddddddd”）；}

但是，没有输出。所以我怀疑它根本无法识别任何击键。但我想不出为什么。如果有人有任何建议，我将不胜感激。显然，我有更多的代码可以共享，如果有人认为它对解决这个bug有用的话。

Answer 1

1）使用KeyBindings KeyListener有两个大问题，第一，你监听所有的键，第二，你必须有焦点和可聚焦。相反，KeyBinding你为一个键绑定，你不必在焦点上。

简单的例子：

AbstractAction escapeAction = new AbstractAction() {
    @Override
    public void actionPerformed(ActionEvent e) {
         //code here example
         ((JComponent)e.getSource()).setVisible(Boolean.FALSE);
    }};
 String key = "ESCAPE";
 KeyStroke keyStroke = KeyStroke.getKeyStroke(key);
 component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(keyStroke, key);
 component.getActionMap().put(key, escapeAction);

可以使用这些JComponent常量

WHEN_ANCESTOR_OF_FOCUSED_COMPONENT 
WHEN_FOCUSED 
WHEN_IN_FOCUSED_WINDOW 

public class Board extends JPanel implements ActionListener{

 public class Board{
   private JPanel panel;

    private class MyActionListener implements ActionListener{
       //code here
    }
  }