Question

写的这个Java小例子不能响应键盘事件是怎么回事？

public class frame extends JFrame{

JLabel lb = new JLabel("hello");
public frame() {
this.setSize(700, 400);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.add(lb);
lb.addKeyListener(new kyeMonitor());
this.setVisible(true);
}

public static void main(String[] args) {
frame f = new frame();
}

private class kyeMonitor extends KeyAdapter {

@Override
public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_ENTER){
lb.setText("Enter text " );
}
}
}

}

Answer 1

给JLabel添加键盘事件，焦点不在Jlabel上的话，不会触发事件