怎么在单个窗口的范围内监听所有键盘事件

public focustest() {//构造方法      ...............      Toolkit tk = Toolkit.getDefaultToolkit();       tk.addAWTEventListener(new GlobalEventListener(),AWTEvent.KEY_EVENT_MASK);  }      class GlobalEventListener implements AWTEventListener {//子类       public void eventDispatched(AWTEvent evt) {           if (evt instanceof KeyEvent) {               KeyEvent kevt = (KeyEvent) evt;               if (kevt.getID() == KeyEvent.KEY_PRESSED) {                   String modifier = KeyEvent.getKeyModifiersText(kevt.getModifiers());                   String key = KeyEvent.getKeyText(kevt.getKeyCode());                   System.out.println("Modifier:"+modifier+"|Key:"+key);               }           }       }  }